xref: /petsc/src/snes/tutorials/ex30.c (revision 327415f76d85372a4417cf1aaa14db707d4d6c04)
1 static const char help[] = "Steady-state 2D subduction flow, pressure and temperature solver.\n\
2        The flow is driven by the subducting slab.\n\
3 ---------------------------------ex30 help---------------------------------\n\
4   -OPTION <DEFAULT> = (UNITS) DESCRIPTION.\n\n\
5   -width <320> = (km) width of domain.\n\
6   -depth <300> = (km) depth of domain.\n\
7   -slab_dip <45> = (degrees) dip angle of the slab (determines the grid aspect ratio).\n\
8   -lid_depth <35> = (km) depth of the static conductive lid.\n\
9   -fault_depth <35> = (km) depth of slab-wedge mechanical coupling\n\
10      (fault dept >= lid depth).\n\
11 \n\
12   -ni <82> = grid cells in x-direction. (nj adjusts to accommodate\n\
13       the slab dip & depth). DO NOT USE -da_grid_x option!!!\n\
14   -ivisc <3> = rheology option.\n\
15       0 --- constant viscosity.\n\
16       1 --- olivine diffusion creep rheology (T&P-dependent, newtonian).\n\
17       2 --- olivine dislocation creep rheology (T&P-dependent, non-newtonian).\n\
18       3 --- Full mantle rheology, combination of 1 & 2.\n\
19 \n\
20   -slab_velocity <5> = (cm/year) convergence rate of slab into subduction zone.\n\
21   -slab_age <50> = (million yrs) age of slab for thermal profile boundary condition.\n\
22   -lid_age <50> = (million yrs) age of lid for thermal profile boundary condition.\n\
23 \n\
24   FOR OTHER PARAMETER OPTIONS AND THEIR DEFAULT VALUES, see SetParams() in ex30.c.\n\
25 ---------------------------------ex30 help---------------------------------\n";
26 
27 /*F-----------------------------------------------------------------------
28 
29     This PETSc 2.2.0 example by Richard F. Katz
30     http://www.ldeo.columbia.edu/~katz/
31 
32     The problem is modeled by the partial differential equation system
33 
34 \begin{eqnarray}
35          -\nabla P + \nabla \cdot [\eta (\nabla v + \nabla v^T)] & = & 0  \\
36                                            \nabla \cdot v & = & 0   \\
37                     dT/dt + \nabla \cdot (vT) - 1/Pe \triangle^2(T) & = & 0  \\
38 \end{eqnarray}
39 
40  \begin{eqnarray}
41         \eta(T,Eps\_dot) &  = & \hbox{constant                        }    \hbox{if ivisc} ==0  \\
42                       &  = & \hbox{diffusion creep (T,P-dependent)    }     \hbox{if ivisc} ==1  \\
43                       &  = & \hbox{dislocation creep (T,P,v-dependent)}  \hbox{if ivisc} ==2  \\
44                       &  = & \hbox{mantle viscosity (difn and disl)   }  \hbox{if ivisc} ==3
45 \end{eqnarray}
46 
47     which is uniformly discretized on a staggered mesh:
48                       -------$w_{ij}$------
49                   $u_{i-1j}$    $P,T_{ij}$   $u_{ij}$
50                       ------$w_{ij-1}$-----
51 
52   ------------------------------------------------------------------------F*/
53 
54 #include <petscsnes.h>
55 #include <petscdm.h>
56 #include <petscdmda.h>
57 
58 #define VISC_CONST   0
59 #define VISC_DIFN    1
60 #define VISC_DISL    2
61 #define VISC_FULL    3
62 #define CELL_CENTER  0
63 #define CELL_CORNER  1
64 #define BC_ANALYTIC  0
65 #define BC_NOSTRESS  1
66 #define BC_EXPERMNT  2
67 #define ADVECT_FV    0
68 #define ADVECT_FROMM 1
69 #define PLATE_SLAB   0
70 #define PLATE_LID    1
71 #define EPS_ZERO     0.00000001
72 
73 typedef struct { /* holds the variables to be solved for */
74   PetscScalar u,w,p,T;
75 } Field;
76 
77 typedef struct { /* parameters needed to compute viscosity */
78   PetscReal A,n,Estar,Vstar;
79 } ViscParam;
80 
81 typedef struct { /* physical and miscelaneous parameters */
82   PetscReal width, depth, scaled_width, scaled_depth, peclet, potentialT;
83   PetscReal slab_dip, slab_age, slab_velocity, kappa, z_scale;
84   PetscReal c, d, sb, cb, skt, visc_cutoff, lid_age, eta0, continuation;
85   PetscReal L, V, lid_depth, fault_depth;
86   ViscParam diffusion, dislocation;
87   PetscInt  ivisc, adv_scheme, ibound, output_ivisc;
88   PetscBool quiet, param_test, output_to_file, pv_analytic;
89   PetscBool interrupted, stop_solve, toggle_kspmon, kspmon;
90   char      filename[PETSC_MAX_PATH_LEN];
91 } Parameter;
92 
93 typedef struct { /* grid parameters */
94   DMBoundaryType   bx,by;
95   DMDAStencilType  stencil;
96   PetscInt         corner,ni,nj,jlid,jfault,inose;
97   PetscInt         dof,stencil_width,mglevels;
98   PetscReal        dx,dz;
99 } GridInfo;
100 
101 typedef struct { /* application context */
102   Vec       x,Xguess;
103   Parameter *param;
104   GridInfo  *grid;
105 } AppCtx;
106 
107 /* Callback functions (static interface) */
108 extern PetscErrorCode FormFunctionLocal(DMDALocalInfo*,Field**,Field**,void*);
109 
110 /* Main routines */
111 extern PetscErrorCode SetParams(Parameter*, GridInfo*);
112 extern PetscErrorCode ReportParams(Parameter*, GridInfo*);
113 extern PetscErrorCode Initialize(DM);
114 extern PetscErrorCode UpdateSolution(SNES,AppCtx*, PetscInt*);
115 extern PetscErrorCode DoOutput(SNES,PetscInt);
116 
117 /* Post-processing & misc */
118 extern PetscErrorCode ViscosityField(DM,Vec,Vec);
119 extern PetscErrorCode StressField(DM);
120 extern PetscErrorCode SNESConverged_Interactive(SNES, PetscInt, PetscReal, PetscReal, PetscReal, SNESConvergedReason*, void*);
121 extern PetscErrorCode InteractiveHandler(int, void*);
122 
123 /*-----------------------------------------------------------------------*/
124 int main(int argc,char **argv)
125 /*-----------------------------------------------------------------------*/
126 {
127   SNES           snes;
128   AppCtx         *user;               /* user-defined work context */
129   Parameter      param;
130   GridInfo       grid;
131   PetscInt       nits;
132   MPI_Comm       comm;
133   DM             da;
134 
135   PetscFunctionBeginUser;
136   PetscCall(PetscInitialize(&argc,&argv,(char*)0,help));
137   PetscOptionsSetValue(NULL,"-file","ex30_output");
138   PetscOptionsSetValue(NULL,"-snes_monitor_short",NULL);
139   PetscOptionsSetValue(NULL,"-snes_max_it","20");
140   PetscOptionsSetValue(NULL,"-ksp_max_it","1500");
141   PetscOptionsSetValue(NULL,"-ksp_gmres_restart","300");
142   PetscOptionsInsert(NULL,&argc,&argv,NULL);
143 
144   comm = PETSC_COMM_WORLD;
145 
146   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
147      Set up the problem parameters.
148      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
149   PetscCall(SetParams(&param,&grid));
150   PetscCall(ReportParams(&param,&grid));
151 
152   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
153      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
154   PetscCall(SNESCreate(comm,&snes));
155   PetscCall(DMDACreate2d(comm,grid.bx,grid.by,grid.stencil,grid.ni,grid.nj,PETSC_DECIDE,PETSC_DECIDE,grid.dof,grid.stencil_width,0,0,&da));
156   PetscCall(DMSetFromOptions(da));
157   PetscCall(DMSetUp(da));
158   PetscCall(SNESSetDM(snes,da));
159   PetscCall(DMDASetFieldName(da,0,"x-velocity"));
160   PetscCall(DMDASetFieldName(da,1,"y-velocity"));
161   PetscCall(DMDASetFieldName(da,2,"pressure"));
162   PetscCall(DMDASetFieldName(da,3,"temperature"));
163 
164   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
165      Create user context, set problem data, create vector data structures.
166      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
167   PetscCall(PetscNew(&user));
168   user->param = &param;
169   user->grid  = &grid;
170   PetscCall(DMSetApplicationContext(da,user));
171   PetscCall(DMCreateGlobalVector(da,&(user->Xguess)));
172 
173   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
174      Set up the SNES solver with callback functions.
175      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
176   PetscCall(DMDASNESSetFunctionLocal(da,INSERT_VALUES,(PetscErrorCode (*)(DMDALocalInfo*,void*,void*,void*))FormFunctionLocal,(void*)user));
177   PetscCall(SNESSetFromOptions(snes));
178 
179   PetscCall(SNESSetConvergenceTest(snes,SNESConverged_Interactive,(void*)user,NULL));
180   PetscCall(PetscPushSignalHandler(InteractiveHandler,(void*)user));
181 
182   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
183      Initialize and solve the nonlinear system
184      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
185   PetscCall(Initialize(da));
186   PetscCall(UpdateSolution(snes,user,&nits));
187 
188   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
189      Output variables.
190      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
191   PetscCall(DoOutput(snes,nits));
192 
193   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
194      Free work space.
195      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
196   PetscCall(VecDestroy(&user->Xguess));
197   PetscCall(VecDestroy(&user->x));
198   PetscCall(PetscFree(user));
199   PetscCall(SNESDestroy(&snes));
200   PetscCall(DMDestroy(&da));
201   PetscCall(PetscPopSignalHandler());
202   PetscCall(PetscFinalize());
203   return 0;
204 }
205 
206 /*=====================================================================
207   PETSc INTERACTION FUNCTIONS (initialize & call SNESSolve)
208   =====================================================================*/
209 
210 /*---------------------------------------------------------------------*/
211 /*  manages solve: adaptive continuation method  */
212 PetscErrorCode UpdateSolution(SNES snes, AppCtx *user, PetscInt *nits)
213 {
214   KSP                 ksp;
215   PC                  pc;
216   SNESConvergedReason reason = SNES_CONVERGED_ITERATING;
217   Parameter           *param   = user->param;
218   PetscReal           cont_incr=0.3;
219   PetscInt            its;
220   PetscBool           q = PETSC_FALSE;
221   DM                  dm;
222 
223   PetscFunctionBeginUser;
224   PetscCall(SNESGetDM(snes,&dm));
225   PetscCall(DMCreateGlobalVector(dm,&user->x));
226   PetscCall(SNESGetKSP(snes,&ksp));
227   PetscCall(KSPGetPC(ksp, &pc));
228   PetscCall(KSPSetComputeSingularValues(ksp, PETSC_TRUE));
229 
230   *nits=0;
231 
232   /* Isoviscous solve */
233   if (param->ivisc == VISC_CONST && !param->stop_solve) {
234     param->ivisc = VISC_CONST;
235 
236     PetscCall(SNESSolve(snes,0,user->x));
237     PetscCall(SNESGetConvergedReason(snes,&reason));
238     PetscCall(SNESGetIterationNumber(snes,&its));
239     *nits += its;
240     PetscCall(VecCopy(user->x,user->Xguess));
241     if (param->stop_solve) goto done;
242   }
243 
244   /* Olivine diffusion creep */
245   if (param->ivisc >= VISC_DIFN && !param->stop_solve) {
246     if (!q) PetscCall(PetscPrintf(PETSC_COMM_WORLD,"Computing Variable Viscosity Solution\n"));
247 
248     /* continuation method on viscosity cutoff */
249     for (param->continuation=0.0;; param->continuation+=cont_incr) {
250       if (!q) PetscCall(PetscPrintf(PETSC_COMM_WORLD," Continuation parameter = %g\n", (double)param->continuation));
251 
252       /* solve the non-linear system */
253       PetscCall(VecCopy(user->Xguess,user->x));
254       PetscCall(SNESSolve(snes,0,user->x));
255       PetscCall(SNESGetConvergedReason(snes,&reason));
256       PetscCall(SNESGetIterationNumber(snes,&its));
257       *nits += its;
258       if (!q) PetscCall(PetscPrintf(PETSC_COMM_WORLD," SNES iterations: %" PetscInt_FMT ", Cumulative: %" PetscInt_FMT "\n", its, *nits));
259       if (param->stop_solve) goto done;
260 
261       if (reason<0) {
262         /* NOT converged */
263         cont_incr = -PetscAbsReal(cont_incr)/2.0;
264         if (PetscAbsReal(cont_incr)<0.01) goto done;
265 
266       } else {
267         /* converged */
268         PetscCall(VecCopy(user->x,user->Xguess));
269         if (param->continuation >= 1.0) goto done;
270         if (its<=3)      cont_incr = 0.30001;
271         else if (its<=8) cont_incr = 0.15001;
272         else             cont_incr = 0.10001;
273 
274         if (param->continuation+cont_incr > 1.0) cont_incr = 1.0 - param->continuation;
275       } /* endif reason<0 */
276     }
277   }
278 done:
279   if (param->stop_solve && !q) PetscCall(PetscPrintf(PETSC_COMM_WORLD,"USER SIGNAL: stopping solve.\n"));
280   if (reason<0 && !q) PetscCall(PetscPrintf(PETSC_COMM_WORLD,"FAILED TO CONVERGE: stopping solve.\n"));
281   PetscFunctionReturn(0);
282 }
283 
284 /*=====================================================================
285   PHYSICS FUNCTIONS (compute the discrete residual)
286   =====================================================================*/
287 
288 /*---------------------------------------------------------------------*/
289 static inline PetscScalar UInterp(Field **x, PetscInt i, PetscInt j)
290 /*---------------------------------------------------------------------*/
291 {
292   return 0.25*(x[j][i].u+x[j+1][i].u+x[j][i+1].u+x[j+1][i+1].u);
293 }
294 
295 /*---------------------------------------------------------------------*/
296 static inline PetscScalar WInterp(Field **x, PetscInt i, PetscInt j)
297 /*---------------------------------------------------------------------*/
298 {
299   return 0.25*(x[j][i].w+x[j+1][i].w+x[j][i+1].w+x[j+1][i+1].w);
300 }
301 
302 /*---------------------------------------------------------------------*/
303 static inline PetscScalar PInterp(Field **x, PetscInt i, PetscInt j)
304 /*---------------------------------------------------------------------*/
305 {
306   return 0.25*(x[j][i].p+x[j+1][i].p+x[j][i+1].p+x[j+1][i+1].p);
307 }
308 
309 /*---------------------------------------------------------------------*/
310 static inline PetscScalar TInterp(Field **x, PetscInt i, PetscInt j)
311 /*---------------------------------------------------------------------*/
312 {
313   return 0.25*(x[j][i].T+x[j+1][i].T+x[j][i+1].T+x[j+1][i+1].T);
314 }
315 
316 /*---------------------------------------------------------------------*/
317 /*  isoviscous analytic solution for IC */
318 static inline PetscScalar HorizVelocity(PetscInt i, PetscInt j, AppCtx *user)
319 /*---------------------------------------------------------------------*/
320 {
321   Parameter   *param = user->param;
322   GridInfo    *grid  = user->grid;
323   PetscScalar st, ct, th, c=param->c, d=param->d;
324   PetscReal   x, z,r;
325 
326   x  = (i - grid->jlid)*grid->dx;  z = (j - grid->jlid - 0.5)*grid->dz;
327   r  = PetscSqrtReal(x*x+z*z);
328   st = z/r;
329   ct = x/r;
330   th = PetscAtanReal(z/x);
331   return ct*(c*th*st+d*(st+th*ct)) + st*(c*(st-th*ct)+d*th*st);
332 }
333 
334 /*---------------------------------------------------------------------*/
335 /*  isoviscous analytic solution for IC */
336 static inline PetscScalar VertVelocity(PetscInt i, PetscInt j, AppCtx *user)
337 /*---------------------------------------------------------------------*/
338 {
339   Parameter   *param = user->param;
340   GridInfo    *grid  = user->grid;
341   PetscScalar st, ct, th, c=param->c, d=param->d;
342   PetscReal   x, z, r;
343 
344   x = (i - grid->jlid - 0.5)*grid->dx;  z = (j - grid->jlid)*grid->dz;
345   r = PetscSqrtReal(x*x+z*z); st = z/r;  ct = x/r;  th = PetscAtanReal(z/x);
346   return st*(c*th*st+d*(st+th*ct)) - ct*(c*(st-th*ct)+d*th*st);
347 }
348 
349 /*---------------------------------------------------------------------*/
350 /*  isoviscous analytic solution for IC */
351 static inline PetscScalar Pressure(PetscInt i, PetscInt j, AppCtx *user)
352 /*---------------------------------------------------------------------*/
353 {
354   Parameter   *param = user->param;
355   GridInfo    *grid  = user->grid;
356   PetscScalar x, z, r, st, ct, c=param->c, d=param->d;
357 
358   x = (i - grid->jlid - 0.5)*grid->dx;  z = (j - grid->jlid - 0.5)*grid->dz;
359   r = PetscSqrtReal(x*x+z*z);  st = z/r;  ct = x/r;
360   return (-2.0*(c*ct-d*st)/r);
361 }
362 
363 /*  computes the second invariant of the strain rate tensor */
364 static inline PetscScalar CalcSecInv(Field **x, PetscInt i, PetscInt j, PetscInt ipos, AppCtx *user)
365 /*---------------------------------------------------------------------*/
366 {
367   Parameter   *param = user->param;
368   GridInfo    *grid  = user->grid;
369   PetscInt    ilim   =grid->ni-1, jlim=grid->nj-1;
370   PetscScalar uN,uS,uE,uW,wN,wS,wE,wW;
371   PetscScalar eps11, eps12, eps22;
372 
373   if (i<j) return EPS_ZERO;
374   if (i==ilim) i--;
375   if (j==jlim) j--;
376 
377   if (ipos==CELL_CENTER) { /* on cell center */
378     if (j<=grid->jlid) return EPS_ZERO;
379 
380     uE = x[j][i].u; uW = x[j][i-1].u;
381     wN = x[j][i].w; wS = x[j-1][i].w;
382     wE = WInterp(x,i,j-1);
383     if (i==j) {
384       uN = param->cb; wW = param->sb;
385     } else {
386       uN = UInterp(x,i-1,j); wW = WInterp(x,i-1,j-1);
387     }
388 
389     if (j==grid->jlid+1) uS = 0.0;
390     else                 uS = UInterp(x,i-1,j-1);
391 
392   } else {       /* on CELL_CORNER */
393     if (j<grid->jlid) return EPS_ZERO;
394 
395     uN = x[j+1][i].u;  uS = x[j][i].u;
396     wE = x[j][i+1].w;  wW = x[j][i].w;
397     if (i==j) {
398       wN = param->sb;
399       uW = param->cb;
400     } else {
401       wN = WInterp(x,i,j);
402       uW = UInterp(x,i-1,j);
403     }
404 
405     if (j==grid->jlid) {
406       uE = 0.0;  uW = 0.0;
407       uS = -uN;
408       wS = -wN;
409     } else {
410       uE = UInterp(x,i,j);
411       wS = WInterp(x,i,j-1);
412     }
413   }
414 
415   eps11 = (uE-uW)/grid->dx;  eps22 = (wN-wS)/grid->dz;
416   eps12 = 0.5*((uN-uS)/grid->dz + (wE-wW)/grid->dx);
417 
418   return PetscSqrtReal(0.5*(eps11*eps11 + 2.0*eps12*eps12 + eps22*eps22));
419 }
420 
421 /*---------------------------------------------------------------------*/
422 /*  computes the shear viscosity */
423 static inline PetscScalar Viscosity(PetscScalar T, PetscScalar eps, PetscScalar z, Parameter *param)
424 /*---------------------------------------------------------------------*/
425 {
426   PetscReal   result   =0.0;
427   ViscParam   difn     =param->diffusion, disl=param->dislocation;
428   PetscInt    iVisc    =param->ivisc;
429   PetscScalar eps_scale=param->V/(param->L*1000.0);
430   PetscScalar strain_power, v1, v2, P;
431   PetscScalar rho_g = 32340.0, R=8.3144;
432 
433   P = rho_g*(z*param->L*1000.0); /* Pa */
434 
435   if (iVisc==VISC_CONST) {
436     /* constant viscosity */
437     return 1.0;
438   } else if (iVisc==VISC_DIFN) {
439     /* diffusion creep rheology */
440     result = PetscRealPart((difn.A*PetscExpScalar((difn.Estar + P*difn.Vstar)/R/(T+273.0))/param->eta0));
441   } else if (iVisc==VISC_DISL) {
442     /* dislocation creep rheology */
443     strain_power = PetscPowScalar(eps*eps_scale, (1.0-disl.n)/disl.n);
444 
445     result = PetscRealPart(disl.A*PetscExpScalar((disl.Estar + P*disl.Vstar)/disl.n/R/(T+273.0))*strain_power/param->eta0);
446   } else if (iVisc==VISC_FULL) {
447     /* dislocation/diffusion creep rheology */
448     strain_power = PetscPowScalar(eps*eps_scale, (1.0-disl.n)/disl.n);
449 
450     v1 = difn.A*PetscExpScalar((difn.Estar + P*difn.Vstar)/R/(T+273.0))/param->eta0;
451     v2 = disl.A*PetscExpScalar((disl.Estar + P*disl.Vstar)/disl.n/R/(T+273.0))*strain_power/param->eta0;
452 
453     result = PetscRealPart(1.0/(1.0/v1 + 1.0/v2));
454   }
455 
456   /* max viscosity is param->eta0 */
457   result = PetscMin(result, 1.0);
458   /* min viscosity is param->visc_cutoff */
459   result = PetscMax(result, param->visc_cutoff);
460   /* continuation method */
461   result = PetscPowReal(result,param->continuation);
462   return result;
463 }
464 
465 /*---------------------------------------------------------------------*/
466 /*  computes the residual of the x-component of eqn (1) above */
467 static inline PetscScalar XMomentumResidual(Field **x, PetscInt i, PetscInt j, AppCtx *user)
468 /*---------------------------------------------------------------------*/
469 {
470   Parameter   *param=user->param;
471   GridInfo    *grid =user->grid;
472   PetscScalar dx    = grid->dx, dz=grid->dz;
473   PetscScalar etaN,etaS,etaE,etaW,epsN=0.0,epsS=0.0,epsE=0.0,epsW=0.0;
474   PetscScalar TE=0.0,TN=0.0,TS=0.0,TW=0.0, dPdx, residual, z_scale;
475   PetscScalar dudxW,dudxE,dudzN,dudzS,dwdxN,dwdxS;
476   PetscInt    jlim = grid->nj-1;
477 
478   z_scale = param->z_scale;
479 
480   if (param->ivisc==VISC_DIFN || param->ivisc>=VISC_DISL) { /* viscosity is T-dependent */
481     TS = param->potentialT * TInterp(x,i,j-1) * PetscExpScalar((j-1.0)*dz*z_scale);
482     if (j==jlim) TN = TS;
483     else         TN = param->potentialT * TInterp(x,i,j) * PetscExpScalar(j*dz*z_scale);
484     TW = param->potentialT * x[j][i].T        * PetscExpScalar((j-0.5)*dz*z_scale);
485     TE = param->potentialT * x[j][i+1].T      * PetscExpScalar((j-0.5)*dz*z_scale);
486     if (param->ivisc>=VISC_DISL) { /* olivine dislocation creep */
487       epsN = CalcSecInv(x,i,j,  CELL_CORNER,user);
488       epsS = CalcSecInv(x,i,j-1,CELL_CORNER,user);
489       epsE = CalcSecInv(x,i+1,j,CELL_CENTER,user);
490       epsW = CalcSecInv(x,i,j,  CELL_CENTER,user);
491     }
492   }
493   etaN = Viscosity(TN,epsN,dz*(j+0.5),param);
494   etaS = Viscosity(TS,epsS,dz*(j-0.5),param);
495   etaW = Viscosity(TW,epsW,dz*j,param);
496   etaE = Viscosity(TE,epsE,dz*j,param);
497 
498   dPdx = (x[j][i+1].p - x[j][i].p)/dx;
499   if (j==jlim) dudzN = etaN * (x[j][i].w   - x[j][i+1].w)/dx;
500   else         dudzN = etaN * (x[j+1][i].u - x[j][i].u)  /dz;
501   dudzS = etaS * (x[j][i].u    - x[j-1][i].u)/dz;
502   dudxE = etaE * (x[j][i+1].u  - x[j][i].u)  /dx;
503   dudxW = etaW * (x[j][i].u    - x[j][i-1].u)/dx;
504 
505   residual = -dPdx                          /* X-MOMENTUM EQUATION*/
506              +(dudxE - dudxW)/dx
507              +(dudzN - dudzS)/dz;
508 
509   if (param->ivisc!=VISC_CONST) {
510     dwdxN = etaN * (x[j][i+1].w   - x[j][i].w)  /dx;
511     dwdxS = etaS * (x[j-1][i+1].w - x[j-1][i].w)/dx;
512 
513     residual += (dudxE - dudxW)/dx + (dwdxN - dwdxS)/dz;
514   }
515 
516   return residual;
517 }
518 
519 /*---------------------------------------------------------------------*/
520 /*  computes the residual of the z-component of eqn (1) above */
521 static inline PetscScalar ZMomentumResidual(Field **x, PetscInt i, PetscInt j, AppCtx *user)
522 /*---------------------------------------------------------------------*/
523 {
524   Parameter   *param=user->param;
525   GridInfo    *grid =user->grid;
526   PetscScalar dx    = grid->dx, dz=grid->dz;
527   PetscScalar etaN  =0.0,etaS=0.0,etaE=0.0,etaW=0.0,epsN=0.0,epsS=0.0,epsE=0.0,epsW=0.0;
528   PetscScalar TE    =0.0,TN=0.0,TS=0.0,TW=0.0, dPdz, residual,z_scale;
529   PetscScalar dudzE,dudzW,dwdxW,dwdxE,dwdzN,dwdzS;
530   PetscInt    ilim = grid->ni-1;
531 
532   /* geometric and other parameters */
533   z_scale = param->z_scale;
534 
535   /* viscosity */
536   if (param->ivisc==VISC_DIFN || param->ivisc>=VISC_DISL) { /* viscosity is T-dependent */
537     TN = param->potentialT * x[j+1][i].T      * PetscExpScalar((j+0.5)*dz*z_scale);
538     TS = param->potentialT * x[j][i].T        * PetscExpScalar((j-0.5)*dz*z_scale);
539     TW = param->potentialT * TInterp(x,i-1,j) * PetscExpScalar(j*dz*z_scale);
540     if (i==ilim) TE = TW;
541     else         TE = param->potentialT * TInterp(x,i,j) * PetscExpScalar(j*dz*z_scale);
542     if (param->ivisc>=VISC_DISL) { /* olivine dislocation creep */
543       epsN = CalcSecInv(x,i,j+1,CELL_CENTER,user);
544       epsS = CalcSecInv(x,i,j,  CELL_CENTER,user);
545       epsE = CalcSecInv(x,i,j,  CELL_CORNER,user);
546       epsW = CalcSecInv(x,i-1,j,CELL_CORNER,user);
547     }
548   }
549   etaN = Viscosity(TN,epsN,dz*(j+1.0),param);
550   etaS = Viscosity(TS,epsS,dz*(j+0.0),param);
551   etaW = Viscosity(TW,epsW,dz*(j+0.5),param);
552   etaE = Viscosity(TE,epsE,dz*(j+0.5),param);
553 
554   dPdz  = (x[j+1][i].p - x[j][i].p)/dz;
555   dwdzN = etaN * (x[j+1][i].w - x[j][i].w)/dz;
556   dwdzS = etaS * (x[j][i].w - x[j-1][i].w)/dz;
557   if (i==ilim) dwdxE = etaE * (x[j][i].u   - x[j+1][i].u)/dz;
558   else         dwdxE = etaE * (x[j][i+1].w - x[j][i].w)  /dx;
559   dwdxW = 2.0*etaW * (x[j][i].w - x[j][i-1].w)/dx;
560 
561   /* Z-MOMENTUM */
562   residual = -dPdz                 /* constant viscosity terms */
563              +(dwdzN - dwdzS)/dz
564              +(dwdxE - dwdxW)/dx;
565 
566   if (param->ivisc!=VISC_CONST) {
567     dudzE = etaE * (x[j+1][i].u - x[j][i].u)/dz;
568     dudzW = etaW * (x[j+1][i-1].u - x[j][i-1].u)/dz;
569 
570     residual += (dwdzN - dwdzS)/dz + (dudzE - dudzW)/dx;
571   }
572 
573   return residual;
574 }
575 
576 /*---------------------------------------------------------------------*/
577 /*  computes the residual of eqn (2) above */
578 static inline PetscScalar ContinuityResidual(Field **x, PetscInt i, PetscInt j, AppCtx *user)
579 /*---------------------------------------------------------------------*/
580 {
581   GridInfo    *grid =user->grid;
582   PetscScalar uE,uW,wN,wS,dudx,dwdz;
583 
584   uW = x[j][i-1].u; uE = x[j][i].u; dudx = (uE - uW)/grid->dx;
585   wS = x[j-1][i].w; wN = x[j][i].w; dwdz = (wN - wS)/grid->dz;
586 
587   return dudx + dwdz;
588 }
589 
590 /*---------------------------------------------------------------------*/
591 /*  computes the residual of eqn (3) above */
592 static inline PetscScalar EnergyResidual(Field **x, PetscInt i, PetscInt j, AppCtx *user)
593 /*---------------------------------------------------------------------*/
594 {
595   Parameter   *param=user->param;
596   GridInfo    *grid =user->grid;
597   PetscScalar dx    = grid->dx, dz=grid->dz;
598   PetscInt    ilim  =grid->ni-1, jlim=grid->nj-1, jlid=grid->jlid;
599   PetscScalar TE, TN, TS, TW, residual;
600   PetscScalar uE,uW,wN,wS;
601   PetscScalar fN,fS,fE,fW,dTdxW,dTdxE,dTdzN,dTdzS;
602 
603   dTdzN = (x[j+1][i].T - x[j][i].T)  /dz;
604   dTdzS = (x[j][i].T   - x[j-1][i].T)/dz;
605   dTdxE = (x[j][i+1].T - x[j][i].T)  /dx;
606   dTdxW = (x[j][i].T   - x[j][i-1].T)/dx;
607 
608   residual = ((dTdzN - dTdzS)/dz + /* diffusion term */
609               (dTdxE - dTdxW)/dx)*dx*dz/param->peclet;
610 
611   if (j<=jlid && i>=j) {
612     /* don't advect in the lid */
613     return residual;
614   } else if (i<j) {
615     /* beneath the slab sfc */
616     uW = uE = param->cb;
617     wS = wN = param->sb;
618   } else {
619     /* advect in the slab and wedge */
620     uW = x[j][i-1].u; uE = x[j][i].u;
621     wS = x[j-1][i].w; wN = x[j][i].w;
622   }
623 
624   if (param->adv_scheme==ADVECT_FV || i==ilim-1 || j==jlim-1 || i==1 || j==1) {
625     /* finite volume advection */
626     TS = (x[j][i].T + x[j-1][i].T)/2.0;
627     TN = (x[j][i].T + x[j+1][i].T)/2.0;
628     TE = (x[j][i].T + x[j][i+1].T)/2.0;
629     TW = (x[j][i].T + x[j][i-1].T)/2.0;
630     fN = wN*TN*dx; fS = wS*TS*dx;
631     fE = uE*TE*dz; fW = uW*TW*dz;
632 
633   } else {
634     /* Fromm advection scheme */
635     fE =     (uE *(-x[j][i+2].T + 5.0*(x[j][i+1].T+x[j][i].T)-x[j][i-1].T)/8.0
636               - PetscAbsScalar(uE)*(-x[j][i+2].T + 3.0*(x[j][i+1].T-x[j][i].T)+x[j][i-1].T)/8.0)*dz;
637     fW =     (uW *(-x[j][i+1].T + 5.0*(x[j][i].T+x[j][i-1].T)-x[j][i-2].T)/8.0
638               - PetscAbsScalar(uW)*(-x[j][i+1].T + 3.0*(x[j][i].T-x[j][i-1].T)+x[j][i-2].T)/8.0)*dz;
639     fN =     (wN *(-x[j+2][i].T + 5.0*(x[j+1][i].T+x[j][i].T)-x[j-1][i].T)/8.0
640               - PetscAbsScalar(wN)*(-x[j+2][i].T + 3.0*(x[j+1][i].T-x[j][i].T)+x[j-1][i].T)/8.0)*dx;
641     fS =     (wS *(-x[j+1][i].T + 5.0*(x[j][i].T+x[j-1][i].T)-x[j-2][i].T)/8.0
642               - PetscAbsScalar(wS)*(-x[j+1][i].T + 3.0*(x[j][i].T-x[j-1][i].T)+x[j-2][i].T)/8.0)*dx;
643   }
644 
645   residual -= (fE - fW + fN - fS);
646 
647   return residual;
648 }
649 
650 /*---------------------------------------------------------------------*/
651 /*  computes the shear stress---used on the boundaries */
652 static inline PetscScalar ShearStress(Field **x, PetscInt i, PetscInt j, PetscInt ipos, AppCtx *user)
653 /*---------------------------------------------------------------------*/
654 {
655   Parameter   *param=user->param;
656   GridInfo    *grid =user->grid;
657   PetscInt    ilim  =grid->ni-1, jlim=grid->nj-1;
658   PetscScalar uN, uS, wE, wW;
659 
660   if (j<=grid->jlid || i<j || i==ilim || j==jlim) return EPS_ZERO;
661 
662   if (ipos==CELL_CENTER) { /* on cell center */
663 
664     wE = WInterp(x,i,j-1);
665     if (i==j) {
666       wW = param->sb;
667       uN = param->cb;
668     } else {
669       wW = WInterp(x,i-1,j-1);
670       uN = UInterp(x,i-1,j);
671     }
672     if (j==grid->jlid+1) uS = 0.0;
673     else                 uS = UInterp(x,i-1,j-1);
674 
675   } else { /* on cell corner */
676 
677     uN = x[j+1][i].u;         uS = x[j][i].u;
678     wW = x[j][i].w;           wE = x[j][i+1].w;
679 
680   }
681 
682   return (uN-uS)/grid->dz + (wE-wW)/grid->dx;
683 }
684 
685 /*---------------------------------------------------------------------*/
686 /*  computes the normal stress---used on the boundaries */
687 static inline PetscScalar XNormalStress(Field **x, PetscInt i, PetscInt j, PetscInt ipos, AppCtx *user)
688 /*---------------------------------------------------------------------*/
689 {
690   Parameter   *param=user->param;
691   GridInfo    *grid =user->grid;
692   PetscScalar dx    = grid->dx, dz=grid->dz;
693   PetscInt    ilim  =grid->ni-1, jlim=grid->nj-1, ivisc;
694   PetscScalar epsC  =0.0, etaC, TC, uE, uW, pC, z_scale;
695   if (i<j || j<=grid->jlid) return EPS_ZERO;
696 
697   ivisc=param->ivisc;  z_scale = param->z_scale;
698 
699   if (ipos==CELL_CENTER) { /* on cell center */
700 
701     TC = param->potentialT * x[j][i].T * PetscExpScalar((j-0.5)*dz*z_scale);
702     if (ivisc>=VISC_DISL) epsC = CalcSecInv(x,i,j,CELL_CENTER,user);
703     etaC = Viscosity(TC,epsC,dz*j,param);
704 
705     uW = x[j][i-1].u;   uE = x[j][i].u;
706     pC = x[j][i].p;
707 
708   } else { /* on cell corner */
709     if (i==ilim || j==jlim) return EPS_ZERO;
710 
711     TC = param->potentialT * TInterp(x,i,j) * PetscExpScalar(j*dz*z_scale);
712     if (ivisc>=VISC_DISL) epsC = CalcSecInv(x,i,j,CELL_CORNER,user);
713     etaC = Viscosity(TC,epsC,dz*(j+0.5),param);
714 
715     if (i==j) uW = param->sb;
716     else      uW = UInterp(x,i-1,j);
717     uE = UInterp(x,i,j); pC = PInterp(x,i,j);
718   }
719 
720   return 2.0*etaC*(uE-uW)/dx - pC;
721 }
722 
723 /*---------------------------------------------------------------------*/
724 /*  computes the normal stress---used on the boundaries */
725 static inline PetscScalar ZNormalStress(Field **x, PetscInt i, PetscInt j, PetscInt ipos, AppCtx *user)
726 /*---------------------------------------------------------------------*/
727 {
728   Parameter   *param=user->param;
729   GridInfo    *grid =user->grid;
730   PetscScalar dz    =grid->dz;
731   PetscInt    ilim  =grid->ni-1, jlim=grid->nj-1, ivisc;
732   PetscScalar epsC  =0.0, etaC, TC;
733   PetscScalar pC, wN, wS, z_scale;
734   if (i<j || j<=grid->jlid) return EPS_ZERO;
735 
736   ivisc=param->ivisc;  z_scale = param->z_scale;
737 
738   if (ipos==CELL_CENTER) { /* on cell center */
739 
740     TC = param->potentialT * x[j][i].T * PetscExpScalar((j-0.5)*dz*z_scale);
741     if (ivisc>=VISC_DISL) epsC = CalcSecInv(x,i,j,CELL_CENTER,user);
742     etaC = Viscosity(TC,epsC,dz*j,param);
743     wN   = x[j][i].w; wS = x[j-1][i].w; pC = x[j][i].p;
744 
745   } else { /* on cell corner */
746     if ((i==ilim) || (j==jlim)) return EPS_ZERO;
747 
748     TC = param->potentialT * TInterp(x,i,j) * PetscExpScalar(j*dz*z_scale);
749     if (ivisc>=VISC_DISL) epsC = CalcSecInv(x,i,j,CELL_CORNER,user);
750     etaC = Viscosity(TC,epsC,dz*(j+0.5),param);
751     if (i==j) wN = param->sb;
752     else      wN = WInterp(x,i,j);
753     wS = WInterp(x,i,j-1); pC = PInterp(x,i,j);
754   }
755 
756   return 2.0*etaC*(wN-wS)/dz - pC;
757 }
758 
759 /*---------------------------------------------------------------------*/
760 
761 /*=====================================================================
762   INITIALIZATION, POST-PROCESSING AND OUTPUT FUNCTIONS
763   =====================================================================*/
764 
765 /*---------------------------------------------------------------------*/
766 /* initializes the problem parameters and checks for
767    command line changes */
768 PetscErrorCode SetParams(Parameter *param, GridInfo *grid)
769 /*---------------------------------------------------------------------*/
770 {
771   PetscReal SEC_PER_YR                     = 3600.00*24.00*365.2500;
772   PetscReal alpha_g_on_cp_units_inverse_km = 4.0e-5*9.8;
773 
774   /* domain geometry */
775   param->slab_dip    = 45.0;
776   param->width       = 320.0;                                              /* km */
777   param->depth       = 300.0;                                              /* km */
778   param->lid_depth   = 35.0;                                               /* km */
779   param->fault_depth = 35.0;                                               /* km */
780 
781   PetscCall(PetscOptionsGetReal(NULL,NULL,"-slab_dip",&(param->slab_dip),NULL));
782   PetscCall(PetscOptionsGetReal(NULL,NULL,"-width",&(param->width),NULL));
783   PetscCall(PetscOptionsGetReal(NULL,NULL,"-depth",&(param->depth),NULL));
784   PetscCall(PetscOptionsGetReal(NULL,NULL,"-lid_depth",&(param->lid_depth),NULL));
785   PetscCall(PetscOptionsGetReal(NULL,NULL,"-fault_depth",&(param->fault_depth),NULL));
786 
787   param->slab_dip = param->slab_dip*PETSC_PI/180.0;                    /* radians */
788 
789   /* grid information */
790   PetscCall(PetscOptionsGetInt(NULL,NULL, "-jfault",&(grid->jfault),NULL));
791   grid->ni = 82;
792   PetscCall(PetscOptionsGetInt(NULL,NULL, "-ni",&(grid->ni),NULL));
793 
794   grid->dx            = param->width/((PetscReal)(grid->ni-2));               /* km */
795   grid->dz            = grid->dx*PetscTanReal(param->slab_dip);               /* km */
796   grid->nj            = (PetscInt)(param->depth/grid->dz + 3.0);         /* gridpoints*/
797   param->depth        = grid->dz*(grid->nj-2);                             /* km */
798   grid->inose         = 0;                                          /* gridpoints*/
799   PetscCall(PetscOptionsGetInt(NULL,NULL,"-inose",&(grid->inose),NULL));
800   grid->bx            = DM_BOUNDARY_NONE;
801   grid->by            = DM_BOUNDARY_NONE;
802   grid->stencil       = DMDA_STENCIL_BOX;
803   grid->dof           = 4;
804   grid->stencil_width = 2;
805   grid->mglevels      = 1;
806 
807   /* boundary conditions */
808   param->pv_analytic = PETSC_FALSE;
809   param->ibound      = BC_NOSTRESS;
810   PetscCall(PetscOptionsGetInt(NULL,NULL,"-ibound",&(param->ibound),NULL));
811 
812   /* physical constants */
813   param->slab_velocity = 5.0;               /* cm/yr */
814   param->slab_age      = 50.0;              /* Ma */
815   param->lid_age       = 50.0;              /* Ma */
816   param->kappa         = 0.7272e-6;         /* m^2/sec */
817   param->potentialT    = 1300.0;            /* degrees C */
818 
819   PetscCall(PetscOptionsGetReal(NULL,NULL,"-slab_velocity",&(param->slab_velocity),NULL));
820   PetscCall(PetscOptionsGetReal(NULL,NULL,"-slab_age",&(param->slab_age),NULL));
821   PetscCall(PetscOptionsGetReal(NULL,NULL,"-lid_age",&(param->lid_age),NULL));
822   PetscCall(PetscOptionsGetReal(NULL,NULL,"-kappa",&(param->kappa),NULL));
823   PetscCall(PetscOptionsGetReal(NULL,NULL,"-potentialT",&(param->potentialT),NULL));
824 
825   /* viscosity */
826   param->ivisc        = 3;                  /* 0=isovisc, 1=difn creep, 2=disl creep, 3=full */
827   param->eta0         = 1e24;               /* Pa-s */
828   param->visc_cutoff  = 0.0;                /* factor of eta_0 */
829   param->continuation = 1.0;
830 
831   /* constants for diffusion creep */
832   param->diffusion.A     = 1.8e7;             /* Pa-s */
833   param->diffusion.n     = 1.0;               /* dim'less */
834   param->diffusion.Estar = 375e3;             /* J/mol */
835   param->diffusion.Vstar = 5e-6;              /* m^3/mol */
836 
837   /* constants for param->dislocationocation creep */
838   param->dislocation.A     = 2.8969e4;        /* Pa-s */
839   param->dislocation.n     = 3.5;             /* dim'less */
840   param->dislocation.Estar = 530e3;           /* J/mol */
841   param->dislocation.Vstar = 14e-6;           /* m^3/mol */
842 
843   PetscCall(PetscOptionsGetInt(NULL,NULL, "-ivisc",&(param->ivisc),NULL));
844   PetscCall(PetscOptionsGetReal(NULL,NULL,"-visc_cutoff",&(param->visc_cutoff),NULL));
845 
846   param->output_ivisc = param->ivisc;
847 
848   PetscCall(PetscOptionsGetInt(NULL,NULL,"-output_ivisc",&(param->output_ivisc),NULL));
849   PetscCall(PetscOptionsGetReal(NULL,NULL,"-vstar",&(param->dislocation.Vstar),NULL));
850 
851   /* output options */
852   param->quiet      = PETSC_FALSE;
853   param->param_test = PETSC_FALSE;
854 
855   PetscCall(PetscOptionsHasName(NULL,NULL,"-quiet",&(param->quiet)));
856   PetscCall(PetscOptionsHasName(NULL,NULL,"-test",&(param->param_test)));
857   PetscCall(PetscOptionsGetString(NULL,NULL,"-file",param->filename,sizeof(param->filename),&(param->output_to_file)));
858 
859   /* advection */
860   param->adv_scheme = ADVECT_FROMM;       /* advection scheme: 0=finite vol, 1=Fromm */
861 
862   PetscCall(PetscOptionsGetInt(NULL,NULL,"-adv_scheme",&(param->adv_scheme),NULL));
863 
864   /* misc. flags */
865   param->stop_solve    = PETSC_FALSE;
866   param->interrupted   = PETSC_FALSE;
867   param->kspmon        = PETSC_FALSE;
868   param->toggle_kspmon = PETSC_FALSE;
869 
870   /* derived parameters for slab angle */
871   param->sb = PetscSinReal(param->slab_dip);
872   param->cb = PetscCosReal(param->slab_dip);
873   param->c  =  param->slab_dip*param->sb/(param->slab_dip*param->slab_dip-param->sb*param->sb);
874   param->d  = (param->slab_dip*param->cb-param->sb)/(param->slab_dip*param->slab_dip-param->sb*param->sb);
875 
876   /* length, velocity and time scale for non-dimensionalization */
877   param->L = PetscMin(param->width,param->depth);               /* km */
878   param->V = param->slab_velocity/100.0/SEC_PER_YR;             /* m/sec */
879 
880   /* other unit conversions and derived parameters */
881   param->scaled_width = param->width/param->L;                  /* dim'less */
882   param->scaled_depth = param->depth/param->L;                  /* dim'less */
883   param->lid_depth    = param->lid_depth/param->L;              /* dim'less */
884   param->fault_depth  = param->fault_depth/param->L;            /* dim'less */
885   grid->dx            = grid->dx/param->L;                      /* dim'less */
886   grid->dz            = grid->dz/param->L;                      /* dim'less */
887   grid->jlid          = (PetscInt)(param->lid_depth/grid->dz);       /* gridcells */
888   grid->jfault        = (PetscInt)(param->fault_depth/grid->dz);     /* gridcells */
889   param->lid_depth    = grid->jlid*grid->dz;                    /* dim'less */
890   param->fault_depth  = grid->jfault*grid->dz;                  /* dim'less */
891   grid->corner        = grid->jlid+1;                           /* gridcells */
892   param->peclet       = param->V                                /* m/sec */
893                         * param->L*1000.0                       /* m */
894                         / param->kappa;                         /* m^2/sec */
895   param->z_scale = param->L * alpha_g_on_cp_units_inverse_km;
896   param->skt     = PetscSqrtReal(param->kappa*param->slab_age*SEC_PER_YR);
897   PetscCall(PetscOptionsGetReal(NULL,NULL,"-peclet",&(param->peclet),NULL));
898 
899   return 0;
900 }
901 
902 /*---------------------------------------------------------------------*/
903 /*  prints a report of the problem parameters to stdout */
904 PetscErrorCode ReportParams(Parameter *param, GridInfo *grid)
905 /*---------------------------------------------------------------------*/
906 {
907   char           date[30];
908 
909   PetscCall(PetscGetDate(date,30));
910 
911   if (!(param->quiet)) {
912     PetscCall(PetscPrintf(PETSC_COMM_WORLD,"---------------------BEGIN ex30 PARAM REPORT-------------------\n"));
913     PetscCall(PetscPrintf(PETSC_COMM_WORLD,"Domain: \n"));
914     PetscCall(PetscPrintf(PETSC_COMM_WORLD,"  Width = %g km,         Depth = %g km\n",(double)param->width,(double)param->depth));
915     PetscCall(PetscPrintf(PETSC_COMM_WORLD,"  Slab dip = %g degrees,  Slab velocity = %g cm/yr\n",(double)(param->slab_dip*180.0/PETSC_PI),(double)param->slab_velocity));
916     PetscCall(PetscPrintf(PETSC_COMM_WORLD,"  Lid depth = %5.2f km,   Fault depth = %5.2f km\n",(double)(param->lid_depth*param->L),(double)(param->fault_depth*param->L)));
917 
918     PetscCall(PetscPrintf(PETSC_COMM_WORLD,"\nGrid: \n"));
919     PetscCall(PetscPrintf(PETSC_COMM_WORLD,"  [ni,nj] = %" PetscInt_FMT ", %" PetscInt_FMT "       [dx,dz] = %g, %g km\n",grid->ni,grid->nj,(double)(grid->dx*param->L),(double)(grid->dz*param->L)));
920     PetscCall(PetscPrintf(PETSC_COMM_WORLD,"  jlid = %3" PetscInt_FMT "              jfault = %3" PetscInt_FMT " \n",grid->jlid,grid->jfault));
921     PetscCall(PetscPrintf(PETSC_COMM_WORLD,"  Pe = %g\n",(double)param->peclet));
922 
923     PetscCall(PetscPrintf(PETSC_COMM_WORLD,"\nRheology:"));
924     if (param->ivisc==VISC_CONST) {
925       PetscCall(PetscPrintf(PETSC_COMM_WORLD,"                 Isoviscous \n"));
926       if (param->pv_analytic) {
927         PetscCall(PetscPrintf(PETSC_COMM_WORLD,"                          Pressure and Velocity prescribed! \n"));
928       }
929     } else if (param->ivisc==VISC_DIFN) {
930       PetscCall(PetscPrintf(PETSC_COMM_WORLD,"                 Diffusion Creep (T-Dependent Newtonian) \n"));
931       PetscCall(PetscPrintf(PETSC_COMM_WORLD,"                          Viscosity range: %g--%g Pa-sec \n",(double)param->eta0,(double)(param->visc_cutoff*param->eta0)));
932     } else if (param->ivisc==VISC_DISL) {
933       PetscCall(PetscPrintf(PETSC_COMM_WORLD,"                 Dislocation Creep (T-Dependent Non-Newtonian) \n"));
934       PetscCall(PetscPrintf(PETSC_COMM_WORLD,"                          Viscosity range: %g--%g Pa-sec \n",(double)param->eta0,(double)(param->visc_cutoff*param->eta0)));
935     } else if (param->ivisc==VISC_FULL) {
936       PetscCall(PetscPrintf(PETSC_COMM_WORLD,"                 Full Rheology \n"));
937       PetscCall(PetscPrintf(PETSC_COMM_WORLD,"                          Viscosity range: %g--%g Pa-sec \n",(double)param->eta0,(double)(param->visc_cutoff*param->eta0)));
938     } else {
939       PetscCall(PetscPrintf(PETSC_COMM_WORLD,"                 Invalid! \n"));
940       return 1;
941     }
942 
943     PetscCall(PetscPrintf(PETSC_COMM_WORLD,"Boundary condition:"));
944     if (param->ibound==BC_ANALYTIC) {
945       PetscCall(PetscPrintf(PETSC_COMM_WORLD,"       Isoviscous Analytic Dirichlet \n"));
946     } else if (param->ibound==BC_NOSTRESS) {
947       PetscCall(PetscPrintf(PETSC_COMM_WORLD,"       Stress-Free (normal & shear stress)\n"));
948     } else if (param->ibound==BC_EXPERMNT) {
949       PetscCall(PetscPrintf(PETSC_COMM_WORLD,"       Experimental boundary condition \n"));
950     } else {
951       PetscCall(PetscPrintf(PETSC_COMM_WORLD,"       Invalid! \n"));
952       return 1;
953     }
954 
955     if (param->output_to_file) {
956 #if defined(PETSC_HAVE_MATLAB_ENGINE)
957       PetscCall(PetscPrintf(PETSC_COMM_WORLD,"Output Destination:       Mat file \"%s\"\n",param->filename));
958 #else
959       PetscCall(PetscPrintf(PETSC_COMM_WORLD,"Output Destination:       PETSc binary file \"%s\"\n",param->filename));
960 #endif
961     }
962     if (param->output_ivisc != param->ivisc) {
963       PetscCall(PetscPrintf(PETSC_COMM_WORLD,"                          Output viscosity: -ivisc %" PetscInt_FMT "\n",param->output_ivisc));
964     }
965 
966     PetscCall(PetscPrintf(PETSC_COMM_WORLD,"---------------------END ex30 PARAM REPORT---------------------\n"));
967   }
968   if (param->param_test) PetscEnd();
969   return 0;
970 }
971 
972 /* ------------------------------------------------------------------- */
973 /*  generates an initial guess using the analytic solution for isoviscous
974     corner flow */
975 PetscErrorCode Initialize(DM da)
976 /* ------------------------------------------------------------------- */
977 {
978   AppCtx         *user;
979   Parameter      *param;
980   GridInfo       *grid;
981   PetscInt       i,j,is,js,im,jm;
982   Field          **x;
983   Vec            Xguess;
984 
985   /* Get the fine grid */
986   PetscCall(DMGetApplicationContext(da,&user));
987   Xguess = user->Xguess;
988   param  = user->param;
989   grid   = user->grid;
990   PetscCall(DMDAGetCorners(da,&is,&js,NULL,&im,&jm,NULL));
991   PetscCall(DMDAVecGetArray(da,Xguess,(void**)&x));
992 
993   /* Compute initial guess */
994   for (j=js; j<js+jm; j++) {
995     for (i=is; i<is+im; i++) {
996       if (i<j)                x[j][i].u = param->cb;
997       else if (j<=grid->jlid) x[j][i].u = 0.0;
998       else                    x[j][i].u = HorizVelocity(i,j,user);
999 
1000       if (i<=j)               x[j][i].w = param->sb;
1001       else if (j<=grid->jlid) x[j][i].w = 0.0;
1002       else                    x[j][i].w = VertVelocity(i,j,user);
1003 
1004       if (i<j || j<=grid->jlid) x[j][i].p = 0.0;
1005       else                      x[j][i].p = Pressure(i,j,user);
1006 
1007       x[j][i].T = PetscMin(grid->dz*(j-0.5),1.0);
1008     }
1009   }
1010 
1011   /* Restore x to Xguess */
1012   PetscCall(DMDAVecRestoreArray(da,Xguess,(void**)&x));
1013 
1014   return 0;
1015 }
1016 
1017 /*---------------------------------------------------------------------*/
1018 /*  controls output to a file */
1019 PetscErrorCode DoOutput(SNES snes, PetscInt its)
1020 /*---------------------------------------------------------------------*/
1021 {
1022   AppCtx         *user;
1023   Parameter      *param;
1024   GridInfo       *grid;
1025   PetscInt       ivt;
1026   PetscMPIInt    rank;
1027   PetscViewer    viewer;
1028   Vec            res, pars;
1029   MPI_Comm       comm;
1030   DM             da;
1031 
1032   PetscCall(SNESGetDM(snes,&da));
1033   PetscCall(DMGetApplicationContext(da,&user));
1034   param = user->param;
1035   grid  = user->grid;
1036   ivt   = param->ivisc;
1037 
1038   param->ivisc = param->output_ivisc;
1039 
1040   /* compute final residual and final viscosity/strain rate fields */
1041   PetscCall(SNESGetFunction(snes, &res, NULL, NULL));
1042   PetscCall(ViscosityField(da, user->x, user->Xguess));
1043 
1044   /* get the communicator and the rank of the processor */
1045   PetscCall(PetscObjectGetComm((PetscObject)snes, &comm));
1046   PetscCallMPI(MPI_Comm_rank(comm, &rank));
1047 
1048   if (param->output_to_file) { /* send output to binary file */
1049     PetscCall(VecCreate(comm, &pars));
1050     if (rank == 0) { /* on processor 0 */
1051       PetscCall(VecSetSizes(pars, 20, PETSC_DETERMINE));
1052       PetscCall(VecSetFromOptions(pars));
1053       PetscCall(VecSetValue(pars,0, (PetscScalar)(grid->ni),INSERT_VALUES));
1054       PetscCall(VecSetValue(pars,1, (PetscScalar)(grid->nj),INSERT_VALUES));
1055       PetscCall(VecSetValue(pars,2, (PetscScalar)(grid->dx),INSERT_VALUES));
1056       PetscCall(VecSetValue(pars,3, (PetscScalar)(grid->dz),INSERT_VALUES));
1057       PetscCall(VecSetValue(pars,4, (PetscScalar)(param->L),INSERT_VALUES));
1058       PetscCall(VecSetValue(pars,5, (PetscScalar)(param->V),INSERT_VALUES));
1059       /* skipped 6 intentionally */
1060       PetscCall(VecSetValue(pars,7, (PetscScalar)(param->slab_dip),INSERT_VALUES));
1061       PetscCall(VecSetValue(pars,8, (PetscScalar)(grid->jlid),INSERT_VALUES));
1062       PetscCall(VecSetValue(pars,9, (PetscScalar)(param->lid_depth),INSERT_VALUES));
1063       PetscCall(VecSetValue(pars,10,(PetscScalar)(grid->jfault),INSERT_VALUES));
1064       PetscCall(VecSetValue(pars,11,(PetscScalar)(param->fault_depth),INSERT_VALUES));
1065       PetscCall(VecSetValue(pars,12,(PetscScalar)(param->potentialT),INSERT_VALUES));
1066       PetscCall(VecSetValue(pars,13,(PetscScalar)(param->ivisc),INSERT_VALUES));
1067       PetscCall(VecSetValue(pars,14,(PetscScalar)(param->visc_cutoff),INSERT_VALUES));
1068       PetscCall(VecSetValue(pars,15,(PetscScalar)(param->ibound),INSERT_VALUES));
1069       PetscCall(VecSetValue(pars,16,(PetscScalar)(its),INSERT_VALUES));
1070     } else { /* on some other processor */
1071       PetscCall(VecSetSizes(pars, 0, PETSC_DETERMINE));
1072       PetscCall(VecSetFromOptions(pars));
1073     }
1074     PetscCall(VecAssemblyBegin(pars)); PetscCall(VecAssemblyEnd(pars));
1075 
1076     /* create viewer */
1077 #if defined(PETSC_HAVE_MATLAB_ENGINE)
1078     PetscCall(PetscViewerMatlabOpen(PETSC_COMM_WORLD,param->filename,FILE_MODE_WRITE,&viewer));
1079 #else
1080     PetscCall(PetscViewerBinaryOpen(PETSC_COMM_WORLD,param->filename,FILE_MODE_WRITE,&viewer));
1081 #endif
1082 
1083     /* send vectors to viewer */
1084     PetscCall(PetscObjectSetName((PetscObject)res,"res"));
1085     PetscCall(VecView(res,viewer));
1086     PetscCall(PetscObjectSetName((PetscObject)user->x,"out"));
1087     PetscCall(VecView(user->x, viewer));
1088     PetscCall(PetscObjectSetName((PetscObject)(user->Xguess),"aux"));
1089     PetscCall(VecView(user->Xguess, viewer));
1090     PetscCall(StressField(da)); /* compute stress fields */
1091     PetscCall(PetscObjectSetName((PetscObject)(user->Xguess),"str"));
1092     PetscCall(VecView(user->Xguess, viewer));
1093     PetscCall(PetscObjectSetName((PetscObject)pars,"par"));
1094     PetscCall(VecView(pars, viewer));
1095 
1096     /* destroy viewer and vector */
1097     PetscCall(PetscViewerDestroy(&viewer));
1098     PetscCall(VecDestroy(&pars));
1099   }
1100 
1101   param->ivisc = ivt;
1102   return 0;
1103 }
1104 
1105 /* ------------------------------------------------------------------- */
1106 /* Compute both the second invariant of the strain rate tensor and the viscosity, at both cell centers and cell corners */
1107 PetscErrorCode ViscosityField(DM da, Vec X, Vec V)
1108 /* ------------------------------------------------------------------- */
1109 {
1110   AppCtx         *user;
1111   Parameter      *param;
1112   GridInfo       *grid;
1113   Vec            localX;
1114   Field          **v, **x;
1115   PetscReal      eps, /* dx,*/ dz, T, epsC, TC;
1116   PetscInt       i,j,is,js,im,jm,ilim,jlim,ivt;
1117 
1118   PetscFunctionBeginUser;
1119   PetscCall(DMGetApplicationContext(da,&user));
1120   param        = user->param;
1121   grid         = user->grid;
1122   ivt          = param->ivisc;
1123   param->ivisc = param->output_ivisc;
1124 
1125   PetscCall(DMGetLocalVector(da, &localX));
1126   PetscCall(DMGlobalToLocalBegin(da, X, INSERT_VALUES, localX));
1127   PetscCall(DMGlobalToLocalEnd(da, X, INSERT_VALUES, localX));
1128   PetscCall(DMDAVecGetArray(da,localX,(void**)&x));
1129   PetscCall(DMDAVecGetArray(da,V,(void**)&v));
1130 
1131   /* Parameters */
1132   /* dx = grid->dx; */ dz = grid->dz;
1133 
1134   ilim = grid->ni-1; jlim = grid->nj-1;
1135 
1136   /* Compute real temperature, strain rate and viscosity */
1137   PetscCall(DMDAGetCorners(da,&is,&js,NULL,&im,&jm,NULL));
1138   for (j=js; j<js+jm; j++) {
1139     for (i=is; i<is+im; i++) {
1140       T = PetscRealPart(param->potentialT * x[j][i].T * PetscExpScalar((j-0.5)*dz*param->z_scale));
1141       if (i<ilim && j<jlim) {
1142         TC = PetscRealPart(param->potentialT * TInterp(x,i,j) * PetscExpScalar(j*dz*param->z_scale));
1143       } else {
1144         TC = T;
1145       }
1146       eps  = PetscRealPart((CalcSecInv(x,i,j,CELL_CENTER,user)));
1147       epsC = PetscRealPart(CalcSecInv(x,i,j,CELL_CORNER,user));
1148 
1149       v[j][i].u = eps;
1150       v[j][i].w = epsC;
1151       v[j][i].p = Viscosity(T,eps,dz*(j-0.5),param);
1152       v[j][i].T = Viscosity(TC,epsC,dz*j,param);
1153     }
1154   }
1155   PetscCall(DMDAVecRestoreArray(da,V,(void**)&v));
1156   PetscCall(DMDAVecRestoreArray(da,localX,(void**)&x));
1157   PetscCall(DMRestoreLocalVector(da, &localX));
1158 
1159   param->ivisc = ivt;
1160   PetscFunctionReturn(0);
1161 }
1162 
1163 /* ------------------------------------------------------------------- */
1164 /* post-processing: compute stress everywhere */
1165 PetscErrorCode StressField(DM da)
1166 /* ------------------------------------------------------------------- */
1167 {
1168   AppCtx         *user;
1169   PetscInt       i,j,is,js,im,jm;
1170   Vec            locVec;
1171   Field          **x, **y;
1172 
1173   PetscCall(DMGetApplicationContext(da,&user));
1174 
1175   /* Get the fine grid of Xguess and X */
1176   PetscCall(DMDAGetCorners(da,&is,&js,NULL,&im,&jm,NULL));
1177   PetscCall(DMDAVecGetArray(da,user->Xguess,(void**)&x));
1178 
1179   PetscCall(DMGetLocalVector(da, &locVec));
1180   PetscCall(DMGlobalToLocalBegin(da, user->x, INSERT_VALUES, locVec));
1181   PetscCall(DMGlobalToLocalEnd(da, user->x, INSERT_VALUES, locVec));
1182   PetscCall(DMDAVecGetArray(da,locVec,(void**)&y));
1183 
1184   /* Compute stress on the corner points */
1185   for (j=js; j<js+jm; j++) {
1186     for (i=is; i<is+im; i++) {
1187       x[j][i].u = ShearStress(y,i,j,CELL_CENTER,user);
1188       x[j][i].w = ShearStress(y,i,j,CELL_CORNER,user);
1189       x[j][i].p = XNormalStress(y,i,j,CELL_CENTER,user);
1190       x[j][i].T = ZNormalStress(y,i,j,CELL_CENTER,user);
1191     }
1192   }
1193 
1194   /* Restore the fine grid of Xguess and X */
1195   PetscCall(DMDAVecRestoreArray(da,user->Xguess,(void**)&x));
1196   PetscCall(DMDAVecRestoreArray(da,locVec,(void**)&y));
1197   PetscCall(DMRestoreLocalVector(da, &locVec));
1198   return 0;
1199 }
1200 
1201 /*=====================================================================
1202   UTILITY FUNCTIONS
1203   =====================================================================*/
1204 
1205 /*---------------------------------------------------------------------*/
1206 /* returns the velocity of the subducting slab and handles fault nodes
1207    for BC */
1208 static inline PetscScalar SlabVel(char c, PetscInt i, PetscInt j, AppCtx *user)
1209 /*---------------------------------------------------------------------*/
1210 {
1211   Parameter *param = user->param;
1212   GridInfo  *grid  = user->grid;
1213 
1214   if (c=='U' || c=='u') {
1215     if (i<j-1) return param->cb;
1216     else if (j<=grid->jfault) return 0.0;
1217     else return param->cb;
1218 
1219   } else {
1220     if (i<j) return param->sb;
1221     else if (j<=grid->jfault) return 0.0;
1222     else return param->sb;
1223   }
1224 }
1225 
1226 /*---------------------------------------------------------------------*/
1227 /*  solution to diffusive half-space cooling model for BC */
1228 static inline PetscScalar PlateModel(PetscInt j, PetscInt plate, AppCtx *user)
1229 /*---------------------------------------------------------------------*/
1230 {
1231   Parameter     *param = user->param;
1232   PetscScalar   z;
1233   if (plate==PLATE_LID) z = (j-0.5)*user->grid->dz;
1234   else z = (j-0.5)*user->grid->dz*param->cb;  /* PLATE_SLAB */
1235 #if defined(PETSC_HAVE_ERF)
1236   return (PetscReal)(erf((double)PetscRealPart(z*param->L/2.0/param->skt)));
1237 #else
1238   (*PetscErrorPrintf)("erf() not available on this machine\n");
1239   MPI_Abort(PETSC_COMM_SELF,1);
1240 #endif
1241 }
1242 
1243 /*=====================================================================
1244   INTERACTIVE SIGNAL HANDLING
1245   =====================================================================*/
1246 
1247 /* ------------------------------------------------------------------- */
1248 PetscErrorCode SNESConverged_Interactive(SNES snes, PetscInt it,PetscReal xnorm, PetscReal snorm, PetscReal fnorm, SNESConvergedReason *reason, void *ctx)
1249 /* ------------------------------------------------------------------- */
1250 {
1251   AppCtx         *user  = (AppCtx*) ctx;
1252   Parameter      *param = user->param;
1253   KSP            ksp;
1254 
1255   PetscFunctionBeginUser;
1256   if (param->interrupted) {
1257     param->interrupted = PETSC_FALSE;
1258     PetscCall(PetscPrintf(PETSC_COMM_WORLD,"USER SIGNAL: exiting SNES solve. \n"));
1259     *reason = SNES_CONVERGED_FNORM_ABS;
1260     PetscFunctionReturn(0);
1261   } else if (param->toggle_kspmon) {
1262     param->toggle_kspmon = PETSC_FALSE;
1263 
1264     PetscCall(SNESGetKSP(snes, &ksp));
1265 
1266     if (param->kspmon) {
1267       PetscCall(KSPMonitorCancel(ksp));
1268 
1269       param->kspmon = PETSC_FALSE;
1270       PetscCall(PetscPrintf(PETSC_COMM_WORLD,"USER SIGNAL: deactivating ksp singular value monitor. \n"));
1271     } else {
1272       PetscViewerAndFormat *vf;
1273       PetscCall(PetscViewerAndFormatCreate(PETSC_VIEWER_STDOUT_WORLD,PETSC_VIEWER_DEFAULT,&vf));
1274       PetscCall(KSPMonitorSet(ksp,(PetscErrorCode (*)(KSP,PetscInt,PetscReal,void*))KSPMonitorSingularValue,vf,(PetscErrorCode (*)(void**))PetscViewerAndFormatDestroy));
1275 
1276       param->kspmon = PETSC_TRUE;
1277       PetscCall(PetscPrintf(PETSC_COMM_WORLD,"USER SIGNAL: activating ksp singular value monitor. \n"));
1278     }
1279   }
1280   PetscFunctionReturn(SNESConvergedDefault(snes,it,xnorm,snorm,fnorm,reason,ctx));
1281 }
1282 
1283 /* ------------------------------------------------------------------- */
1284 #include <signal.h>
1285 PetscErrorCode InteractiveHandler(int signum, void *ctx)
1286 /* ------------------------------------------------------------------- */
1287 {
1288   AppCtx    *user  = (AppCtx*) ctx;
1289   Parameter *param = user->param;
1290 
1291   if (signum == SIGILL) {
1292     param->toggle_kspmon = PETSC_TRUE;
1293 #if !defined(PETSC_MISSING_SIGCONT)
1294   } else if (signum == SIGCONT) {
1295     param->interrupted = PETSC_TRUE;
1296 #endif
1297 #if !defined(PETSC_MISSING_SIGURG)
1298   } else if (signum == SIGURG) {
1299     param->stop_solve = PETSC_TRUE;
1300 #endif
1301   }
1302   return 0;
1303 }
1304 
1305 /*---------------------------------------------------------------------*/
1306 /*  main call-back function that computes the processor-local piece
1307     of the residual */
1308 PetscErrorCode FormFunctionLocal(DMDALocalInfo *info,Field **x,Field **f,void *ptr)
1309 /*---------------------------------------------------------------------*/
1310 {
1311   AppCtx      *user  = (AppCtx*)ptr;
1312   Parameter   *param = user->param;
1313   GridInfo    *grid  = user->grid;
1314   PetscScalar mag_w, mag_u;
1315   PetscInt    i,j,mx,mz,ilim,jlim;
1316   PetscInt    is,ie,js,je,ibound;    /* ,ivisc */
1317 
1318   PetscFunctionBeginUser;
1319   /* Define global and local grid parameters */
1320   mx   = info->mx;     mz   = info->my;
1321   ilim = mx-1;         jlim = mz-1;
1322   is   = info->xs;     ie   = info->xs+info->xm;
1323   js   = info->ys;     je   = info->ys+info->ym;
1324 
1325   /* Define geometric and numeric parameters */
1326   /* ivisc = param->ivisc; */ ibound = param->ibound;
1327 
1328   for (j=js; j<je; j++) {
1329     for (i=is; i<ie; i++) {
1330 
1331       /************* X-MOMENTUM/VELOCITY *************/
1332       if (i<j) f[j][i].u = x[j][i].u - SlabVel('U',i,j,user);
1333       else if (j<=grid->jlid || (j<grid->corner+grid->inose && i<grid->corner+grid->inose)) {
1334         /* in the lithospheric lid */
1335         f[j][i].u = x[j][i].u - 0.0;
1336       } else if (i==ilim) {
1337         /* on the right side boundary */
1338         if (ibound==BC_ANALYTIC) {
1339           f[j][i].u = x[j][i].u - HorizVelocity(i,j,user);
1340         } else {
1341           f[j][i].u = XNormalStress(x,i,j,CELL_CENTER,user) - EPS_ZERO;
1342         }
1343 
1344       } else if (j==jlim) {
1345         /* on the bottom boundary */
1346         if (ibound==BC_ANALYTIC) {
1347           f[j][i].u = x[j][i].u - HorizVelocity(i,j,user);
1348         } else if (ibound==BC_NOSTRESS) {
1349           f[j][i].u = XMomentumResidual(x,i,j,user);
1350         } else {
1351           /* experimental boundary condition */
1352         }
1353 
1354       } else {
1355         /* in the mantle wedge */
1356         f[j][i].u = XMomentumResidual(x,i,j,user);
1357       }
1358 
1359       /************* Z-MOMENTUM/VELOCITY *************/
1360       if (i<=j) {
1361         f[j][i].w = x[j][i].w - SlabVel('W',i,j,user);
1362 
1363       } else if (j<=grid->jlid || (j<grid->corner+grid->inose && i<grid->corner+grid->inose)) {
1364         /* in the lithospheric lid */
1365         f[j][i].w = x[j][i].w - 0.0;
1366 
1367       } else if (j==jlim) {
1368         /* on the bottom boundary */
1369         if (ibound==BC_ANALYTIC) {
1370           f[j][i].w = x[j][i].w - VertVelocity(i,j,user);
1371         } else {
1372           f[j][i].w = ZNormalStress(x,i,j,CELL_CENTER,user) - EPS_ZERO;
1373         }
1374 
1375       } else if (i==ilim) {
1376         /* on the right side boundary */
1377         if (ibound==BC_ANALYTIC) {
1378           f[j][i].w = x[j][i].w - VertVelocity(i,j,user);
1379         } else if (ibound==BC_NOSTRESS) {
1380           f[j][i].w = ZMomentumResidual(x,i,j,user);
1381         } else {
1382           /* experimental boundary condition */
1383         }
1384 
1385       } else {
1386         /* in the mantle wedge */
1387         f[j][i].w =  ZMomentumResidual(x,i,j,user);
1388       }
1389 
1390       /************* CONTINUITY/PRESSURE *************/
1391       if (i<j || j<=grid->jlid || (j<grid->corner+grid->inose && i<grid->corner+grid->inose)) {
1392         /* in the lid or slab */
1393         f[j][i].p = x[j][i].p;
1394 
1395       } else if ((i==ilim || j==jlim) && ibound==BC_ANALYTIC) {
1396         /* on an analytic boundary */
1397         f[j][i].p = x[j][i].p - Pressure(i,j,user);
1398 
1399       } else {
1400         /* in the mantle wedge */
1401         f[j][i].p = ContinuityResidual(x,i,j,user);
1402       }
1403 
1404       /************* TEMPERATURE *************/
1405       if (j==0) {
1406         /* on the surface */
1407         f[j][i].T = x[j][i].T + x[j+1][i].T + PetscMax(PetscRealPart(x[j][i].T),0.0);
1408 
1409       } else if (i==0) {
1410         /* slab inflow boundary */
1411         f[j][i].T = x[j][i].T - PlateModel(j,PLATE_SLAB,user);
1412 
1413       } else if (i==ilim) {
1414         /* right side boundary */
1415         mag_u = 1.0 - PetscPowRealInt((1.0-PetscMax(PetscMin(PetscRealPart(x[j][i-1].u)/param->cb,1.0),0.0)), 5);
1416         f[j][i].T = x[j][i].T - mag_u*x[j-1][i-1].T - (1.0-mag_u)*PlateModel(j,PLATE_LID,user);
1417 
1418       } else if (j==jlim) {
1419         /* bottom boundary */
1420         mag_w = 1.0 - PetscPowRealInt((1.0-PetscMax(PetscMin(PetscRealPart(x[j-1][i].w)/param->sb,1.0),0.0)), 5);
1421         f[j][i].T = x[j][i].T - mag_w*x[j-1][i-1].T - (1.0-mag_w);
1422 
1423       } else {
1424         /* in the mantle wedge */
1425         f[j][i].T = EnergyResidual(x,i,j,user);
1426       }
1427     }
1428   }
1429   PetscFunctionReturn(0);
1430 }
1431 
1432 /*TEST
1433 
1434    build:
1435       requires: !complex erf
1436 
1437    test:
1438       args: -ni 18
1439       filter: grep -v Destination
1440       requires: !single
1441 
1442 TEST*/
1443