xref: /petsc/src/tao/constrained/tutorials/tomographyADMM.c (revision 6a98f8dc3f2c9149905a87dc2e9d0fedaf64e09a)
1 #include <petsctao.h>
2 /*
3 Description:   ADMM tomography reconstruction example .
4                0.5*||Ax-b||^2 + lambda*g(x)
5 Reference:     BRGN Tomography Example
6 */
7 
8 static char help[] = "Finds the ADMM solution to the under constraint linear model Ax = b, with regularizer. \n\
9                       A is a M*N real matrix (M<N), x is sparse. A good regularizer is an L1 regularizer. \n\
10                       We first split the operator into 0.5*||Ax-b||^2, f(x), and lambda*||x||_1, g(z), where lambda is user specified weight. \n\
11                       g(z) could be either ||z||_1, or ||z||_2^2. Default closed form solution for NORM1 would be soft-threshold, which is \n\
12                       natively supported in admm.c with -tao_admm_regularizer_type soft-threshold. Or user can use regular TAO solver for  \n\
13                       either NORM1 or NORM2 or TAOSHELL, with -reg {1,2,3} \n\
14                       Then, we augment both f and g, and solve it via ADMM. \n\
15                       D is the M*N transform matrix so that D*x is sparse. \n";
16 
17 typedef struct {
18   PetscInt  M,N,K,reg;
19   PetscReal lambda,eps,mumin;
20   Mat       A,ATA,H,Hx,D,Hz,DTD,HF;
21   Vec       c,xlb,xub,x,b,workM,workN,workN2,workN3,xGT;    /* observation b, ground truth xGT, the lower bound and upper bound of x*/
22 } AppCtx;
23 
24 /*------------------------------------------------------------*/
25 
26 PetscErrorCode NullJacobian(Tao tao,Vec X,Mat J,Mat Jpre,void *ptr)
27 {
28   PetscFunctionBegin;
29   PetscFunctionReturn(0);
30 }
31 
32 /*------------------------------------------------------------*/
33 
34 static PetscErrorCode TaoShellSolve_SoftThreshold(Tao tao)
35 {
36   PetscErrorCode ierr;
37   PetscReal      lambda, mu;
38   AppCtx         *user;
39   Vec            out,work,y,x;
40   Tao            admm_tao,misfit;
41 
42   PetscFunctionBegin;
43   user = NULL;
44   mu   = 0;
45   ierr = TaoGetADMMParentTao(tao,&admm_tao);CHKERRQ(ierr);
46   ierr = TaoADMMGetMisfitSubsolver(admm_tao, &misfit);CHKERRQ(ierr);
47   ierr = TaoADMMGetSpectralPenalty(admm_tao,&mu);CHKERRQ(ierr);
48   ierr = TaoShellGetContext(tao, (void**) &user);CHKERRQ(ierr);
49 
50   lambda = user->lambda;
51   work   = user->workN;
52   ierr   = TaoGetSolutionVector(tao, &out);CHKERRQ(ierr);
53   ierr   = TaoGetSolutionVector(misfit, &x);CHKERRQ(ierr);
54   ierr   = TaoADMMGetDualVector(admm_tao, &y);CHKERRQ(ierr);
55 
56   /* Dx + y/mu */
57   ierr = MatMult(user->D,x,work);CHKERRQ(ierr);
58   ierr = VecAXPY(work,1/mu,y);CHKERRQ(ierr);
59 
60   /* soft thresholding */
61   ierr = TaoSoftThreshold(work, -lambda/mu, lambda/mu, out);CHKERRQ(ierr);
62   PetscFunctionReturn(0);
63 }
64 
65 /*------------------------------------------------------------*/
66 
67 PetscErrorCode MisfitObjectiveAndGradient(Tao tao,Vec X,PetscReal *f,Vec g,void *ptr)
68 {
69   AppCtx         *user = (AppCtx*)ptr;
70   PetscErrorCode ierr;
71 
72   PetscFunctionBegin;
73   /* Objective  0.5*||Ax-b||_2^2 */
74   ierr = MatMult(user->A,X,user->workM);CHKERRQ(ierr);
75   ierr = VecAXPY(user->workM,-1,user->b);CHKERRQ(ierr);
76   ierr = VecDot(user->workM,user->workM,f);CHKERRQ(ierr);
77   *f  *= 0.5;
78   /* Gradient. ATAx-ATb */
79   ierr = MatMult(user->ATA,X,user->workN);CHKERRQ(ierr);
80   ierr = MatMultTranspose(user->A,user->b,user->workN2);CHKERRQ(ierr);
81   ierr = VecWAXPY(g,-1.,user->workN2,user->workN);CHKERRQ(ierr);
82   PetscFunctionReturn(0);
83 }
84 
85 /*------------------------------------------------------------*/
86 
87 PetscErrorCode RegularizerObjectiveAndGradient1(Tao tao,Vec X,PetscReal *f_reg,Vec G_reg,void *ptr)
88 {
89   AppCtx         *user = (AppCtx*)ptr;
90   PetscErrorCode ierr;
91 
92   PetscFunctionBegin;
93   /* compute regularizer objective
94    * f = f + lambda*sum(sqrt(y.^2+epsilon^2) - epsilon), where y = D*x */
95   ierr    = VecCopy(X,user->workN2);CHKERRQ(ierr);
96   ierr    = VecPow(user->workN2,2.);CHKERRQ(ierr);
97   ierr    = VecShift(user->workN2,user->eps*user->eps);CHKERRQ(ierr);
98   ierr    = VecSqrtAbs(user->workN2);CHKERRQ(ierr);
99   ierr    = VecCopy(user->workN2, user->workN3);CHKERRQ(ierr);
100   ierr    = VecShift(user->workN2,-user->eps);CHKERRQ(ierr);
101   ierr    = VecSum(user->workN2,f_reg);CHKERRQ(ierr);
102   *f_reg *= user->lambda;
103   /* compute regularizer gradient = lambda*x */
104   ierr = VecPointwiseDivide(G_reg,X,user->workN3);CHKERRQ(ierr);
105   ierr = VecScale(G_reg,user->lambda);CHKERRQ(ierr);
106   PetscFunctionReturn(0);
107 }
108 
109 /*------------------------------------------------------------*/
110 
111 PetscErrorCode RegularizerObjectiveAndGradient2(Tao tao,Vec X,PetscReal *f_reg,Vec G_reg,void *ptr)
112 {
113   AppCtx         *user = (AppCtx*)ptr;
114   PetscErrorCode ierr;
115   PetscReal      temp;
116 
117   PetscFunctionBegin;
118   /* compute regularizer objective = lambda*|z|_2^2 */
119   ierr   = VecDot(X,X,&temp);CHKERRQ(ierr);
120   *f_reg = 0.5*user->lambda*temp;
121   /* compute regularizer gradient = lambda*z */
122   ierr = VecCopy(X,G_reg);
123   ierr = VecScale(G_reg,user->lambda);CHKERRQ(ierr);
124   PetscFunctionReturn(0);
125 }
126 
127 /*------------------------------------------------------------*/
128 
129 static PetscErrorCode HessianMisfit(Tao tao, Vec x, Mat H, Mat Hpre, void *ptr)
130 {
131   PetscFunctionBegin;
132   PetscFunctionReturn(0);
133 }
134 
135 /*------------------------------------------------------------*/
136 
137 static PetscErrorCode HessianReg(Tao tao, Vec x, Mat H, Mat Hpre, void *ptr)
138 {
139   AppCtx         *user = (AppCtx*)ptr;
140   PetscErrorCode ierr;
141 
142   PetscFunctionBegin;
143   ierr = MatMult(user->D,x,user->workN);CHKERRQ(ierr);
144   ierr = VecPow(user->workN2,2.);CHKERRQ(ierr);
145   ierr = VecShift(user->workN2,user->eps*user->eps);CHKERRQ(ierr);
146   ierr = VecSqrtAbs(user->workN2);CHKERRQ(ierr);
147   ierr = VecShift(user->workN2,-user->eps);CHKERRQ(ierr);
148   ierr = VecReciprocal(user->workN2);CHKERRQ(ierr);
149   ierr = VecScale(user->workN2,user->eps*user->eps);CHKERRQ(ierr);
150   ierr = MatDiagonalSet(H,user->workN2,INSERT_VALUES);CHKERRQ(ierr);
151   PetscFunctionReturn(0);
152 }
153 
154 /*------------------------------------------------------------*/
155 
156 PetscErrorCode FullObjGrad(Tao tao,Vec X,PetscReal *f,Vec g,void *ptr)
157 {
158   AppCtx         *user = (AppCtx*)ptr;
159   PetscErrorCode ierr;
160   PetscReal      f_reg;
161 
162   PetscFunctionBegin;
163   /* Objective  0.5*||Ax-b||_2^2 + lambda*||x||_2^2*/
164   ierr = MatMult(user->A,X,user->workM);CHKERRQ(ierr);
165   ierr = VecAXPY(user->workM,-1,user->b);CHKERRQ(ierr);
166   ierr = VecDot(user->workM,user->workM,f);CHKERRQ(ierr);
167   ierr = VecNorm(X,NORM_2,&f_reg);CHKERRQ(ierr);
168   *f  *= 0.5;
169   *f  += user->lambda*f_reg*f_reg;
170   /* Gradient. ATAx-ATb + 2*lambda*x */
171   ierr = MatMult(user->ATA,X,user->workN);CHKERRQ(ierr);
172   ierr = MatMultTranspose(user->A,user->b,user->workN2);CHKERRQ(ierr);
173   ierr = VecWAXPY(g,-1.,user->workN2,user->workN);CHKERRQ(ierr);
174   ierr = VecAXPY(g,2*user->lambda,X);CHKERRQ(ierr);
175   PetscFunctionReturn(0);
176 }
177 /*------------------------------------------------------------*/
178 
179 static PetscErrorCode HessianFull(Tao tao, Vec x, Mat H, Mat Hpre, void *ptr)
180 {
181   PetscFunctionBegin;
182   PetscFunctionReturn(0);
183 }
184 /*------------------------------------------------------------*/
185 
186 
187 PetscErrorCode InitializeUserData(AppCtx *user)
188 {
189   char           dataFile[] = "tomographyData_A_b_xGT";   /* Matrix A and vectors b, xGT(ground truth) binary files generated by Matlab. Debug: change from "tomographyData_A_b_xGT" to "cs1Data_A_b_xGT". */
190   PetscViewer    fd;   /* used to load data from file */
191   PetscErrorCode ierr;
192   PetscInt       k,n;
193   PetscScalar    v;
194   PetscFunctionBegin;
195 
196   /* Load the A matrix, b vector, and xGT vector from a binary file. */
197   ierr = PetscViewerBinaryOpen(PETSC_COMM_WORLD,dataFile,FILE_MODE_READ,&fd);CHKERRQ(ierr);
198   ierr = MatCreate(PETSC_COMM_WORLD,&user->A);CHKERRQ(ierr);
199   ierr = MatSetType(user->A,MATAIJ);CHKERRQ(ierr);
200   ierr = MatLoad(user->A,fd);CHKERRQ(ierr);
201   ierr = VecCreate(PETSC_COMM_WORLD,&user->b);CHKERRQ(ierr);
202   ierr = VecLoad(user->b,fd);CHKERRQ(ierr);
203   ierr = VecCreate(PETSC_COMM_WORLD,&user->xGT);CHKERRQ(ierr);
204   ierr = VecLoad(user->xGT,fd);CHKERRQ(ierr);
205   ierr = PetscViewerDestroy(&fd);CHKERRQ(ierr);
206 
207   ierr = MatGetSize(user->A,&user->M,&user->N);CHKERRQ(ierr);
208 
209   ierr = MatCreate(PETSC_COMM_WORLD,&user->D);CHKERRQ(ierr);
210   ierr = MatSetSizes(user->D,PETSC_DECIDE,PETSC_DECIDE,user->N,user->N);CHKERRQ(ierr);
211   ierr = MatSetFromOptions(user->D);CHKERRQ(ierr);
212   ierr = MatSetUp(user->D);CHKERRQ(ierr);
213   for (k=0; k<user->N; k++) {
214     v = 1.0;
215     n = k+1;
216     if (k< user->N -1) {
217       ierr = MatSetValues(user->D,1,&k,1,&n,&v,INSERT_VALUES);CHKERRQ(ierr);
218     }
219     v    = -1.0;
220     ierr = MatSetValues(user->D,1,&k,1,&k,&v,INSERT_VALUES);CHKERRQ(ierr);
221   }
222   ierr = MatAssemblyBegin(user->D,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
223   ierr = MatAssemblyEnd(user->D,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
224 
225   ierr = MatTransposeMatMult(user->D,user->D,MAT_INITIAL_MATRIX,PETSC_DEFAULT,&user->DTD);CHKERRQ(ierr);
226 
227   ierr = MatCreate(PETSC_COMM_WORLD,&user->Hz);CHKERRQ(ierr);
228   ierr = MatSetSizes(user->Hz,PETSC_DECIDE,PETSC_DECIDE,user->N,user->N);CHKERRQ(ierr);
229   ierr = MatSetFromOptions(user->Hz);CHKERRQ(ierr);
230   ierr = MatSetUp(user->Hz);CHKERRQ(ierr);
231   ierr = MatAssemblyBegin(user->Hz,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
232   ierr = MatAssemblyEnd(user->Hz,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
233 
234   ierr = VecCreate(PETSC_COMM_WORLD,&(user->x));CHKERRQ(ierr);
235   ierr = VecCreate(PETSC_COMM_WORLD,&(user->workM));CHKERRQ(ierr);
236   ierr = VecCreate(PETSC_COMM_WORLD,&(user->workN));CHKERRQ(ierr);
237   ierr = VecCreate(PETSC_COMM_WORLD,&(user->workN2));CHKERRQ(ierr);
238   ierr = VecSetSizes(user->x,PETSC_DECIDE,user->N);CHKERRQ(ierr);
239   ierr = VecSetSizes(user->workM,PETSC_DECIDE,user->M);CHKERRQ(ierr);
240   ierr = VecSetSizes(user->workN,PETSC_DECIDE,user->N);CHKERRQ(ierr);
241   ierr = VecSetSizes(user->workN2,PETSC_DECIDE,user->N);CHKERRQ(ierr);
242   ierr = VecSetFromOptions(user->x);CHKERRQ(ierr);
243   ierr = VecSetFromOptions(user->workM);CHKERRQ(ierr);
244   ierr = VecSetFromOptions(user->workN);CHKERRQ(ierr);
245   ierr = VecSetFromOptions(user->workN2);CHKERRQ(ierr);
246 
247   ierr = VecDuplicate(user->workN,&(user->workN3));CHKERRQ(ierr);
248   ierr = VecDuplicate(user->x,&(user->xlb));CHKERRQ(ierr);
249   ierr = VecDuplicate(user->x,&(user->xub));CHKERRQ(ierr);
250   ierr = VecDuplicate(user->x,&(user->c));CHKERRQ(ierr);
251   ierr = VecSet(user->xlb,0.0);CHKERRQ(ierr);
252   ierr = VecSet(user->c,0.0);CHKERRQ(ierr);
253   ierr = VecSet(user->xub,PETSC_INFINITY);CHKERRQ(ierr);
254 
255   ierr = MatTransposeMatMult(user->A,user->A, MAT_INITIAL_MATRIX, PETSC_DEFAULT, &(user->ATA));CHKERRQ(ierr);
256   ierr = MatTransposeMatMult(user->A,user->A, MAT_INITIAL_MATRIX, PETSC_DEFAULT, &(user->Hx));CHKERRQ(ierr);
257   ierr = MatTransposeMatMult(user->A,user->A, MAT_INITIAL_MATRIX, PETSC_DEFAULT, &(user->HF));CHKERRQ(ierr);
258 
259   ierr = MatAssemblyBegin(user->ATA,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
260   ierr = MatAssemblyEnd(user->ATA,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
261   ierr = MatAssemblyBegin(user->Hx,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
262   ierr = MatAssemblyEnd(user->Hx,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
263   ierr = MatAssemblyBegin(user->HF,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
264   ierr = MatAssemblyEnd(user->HF,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
265 
266   user->lambda = 1.e-8;
267   user->eps    = 1.e-3;
268   user->reg    = 2;
269   user->mumin  = 5.e-6;
270 
271   ierr = PetscOptionsBegin(PETSC_COMM_WORLD, NULL, "Configure separable objection example", "tomographyADMM.c");CHKERRQ(ierr);
272   ierr = PetscOptionsInt("-reg","Regularization scheme for z solver (1,2)", "tomographyADMM.c", user->reg, &(user->reg), NULL);CHKERRQ(ierr);
273   ierr = PetscOptionsReal("-lambda", "The regularization multiplier. 1 default", "tomographyADMM.c", user->lambda, &(user->lambda), NULL);CHKERRQ(ierr);
274   ierr = PetscOptionsReal("-eps", "L1 norm epsilon padding", "tomographyADMM.c", user->eps, &(user->eps), NULL);CHKERRQ(ierr);
275   ierr = PetscOptionsReal("-mumin", "Minimum value for ADMM spectral penalty", "tomographyADMM.c", user->mumin, &(user->mumin), NULL);CHKERRQ(ierr);
276   ierr = PetscOptionsEnd();CHKERRQ(ierr);
277   PetscFunctionReturn(0);
278 }
279 
280 /*------------------------------------------------------------*/
281 
282 PetscErrorCode DestroyContext(AppCtx *user)
283 {
284   PetscErrorCode ierr;
285 
286   PetscFunctionBegin;
287   ierr = MatDestroy(&user->A);CHKERRQ(ierr);
288   ierr = MatDestroy(&user->ATA);CHKERRQ(ierr);
289   ierr = MatDestroy(&user->Hx);CHKERRQ(ierr);
290   ierr = MatDestroy(&user->Hz);CHKERRQ(ierr);
291   ierr = MatDestroy(&user->HF);CHKERRQ(ierr);
292   ierr = MatDestroy(&user->D);CHKERRQ(ierr);
293   ierr = MatDestroy(&user->DTD);CHKERRQ(ierr);
294   ierr = VecDestroy(&user->xGT);CHKERRQ(ierr);
295   ierr = VecDestroy(&user->xlb);CHKERRQ(ierr);
296   ierr = VecDestroy(&user->xub);CHKERRQ(ierr);
297   ierr = VecDestroy(&user->b);CHKERRQ(ierr);
298   ierr = VecDestroy(&user->x);CHKERRQ(ierr);
299   ierr = VecDestroy(&user->c);CHKERRQ(ierr);
300   ierr = VecDestroy(&user->workN3);CHKERRQ(ierr);
301   ierr = VecDestroy(&user->workN2);CHKERRQ(ierr);
302   ierr = VecDestroy(&user->workN);CHKERRQ(ierr);
303   ierr = VecDestroy(&user->workM);CHKERRQ(ierr);
304   PetscFunctionReturn(0);
305 }
306 
307 /*------------------------------------------------------------*/
308 
309 int main(int argc,char **argv)
310 {
311   PetscErrorCode ierr;
312   Tao            tao,misfit,reg;
313   PetscReal      v1,v2;
314   AppCtx*        user;
315   PetscViewer    fd;
316   char           resultFile[] = "tomographyResult_x";
317 
318   ierr = PetscInitialize(&argc,&argv,(char*)0,help);if (ierr) return ierr;
319   ierr = PetscNew(&user);CHKERRQ(ierr);
320   ierr = InitializeUserData(user);CHKERRQ(ierr);
321 
322   ierr = TaoCreate(PETSC_COMM_WORLD, &tao);CHKERRQ(ierr);
323   ierr = TaoSetType(tao, TAOADMM);CHKERRQ(ierr);
324   ierr = TaoSetInitialVector(tao, user->x);CHKERRQ(ierr);
325   /* f(x) + g(x) for parent tao */
326   ierr = TaoADMMSetSpectralPenalty(tao,1.);CHKERRQ(ierr);
327   ierr = TaoSetObjectiveAndGradientRoutine(tao, FullObjGrad, (void*)user);CHKERRQ(ierr);
328   ierr = MatShift(user->HF,user->lambda);CHKERRQ(ierr);
329   ierr = TaoSetHessianRoutine(tao, user->HF, user->HF, HessianFull, (void*)user);CHKERRQ(ierr);
330 
331   /* f(x) for misfit tao */
332   ierr = TaoADMMSetMisfitObjectiveAndGradientRoutine(tao, MisfitObjectiveAndGradient, (void*)user);CHKERRQ(ierr);
333   ierr = TaoADMMSetMisfitHessianRoutine(tao, user->Hx, user->Hx, HessianMisfit, (void*)user);CHKERRQ(ierr);
334   ierr = TaoADMMSetMisfitHessianChangeStatus(tao,PETSC_FALSE);CHKERRQ(ierr);
335   ierr = TaoADMMSetMisfitConstraintJacobian(tao,user->D,user->D,NullJacobian,(void*)user);CHKERRQ(ierr);
336 
337   /* g(x) for regularizer tao */
338   if (user->reg == 1) {
339     ierr = TaoADMMSetRegularizerObjectiveAndGradientRoutine(tao, RegularizerObjectiveAndGradient1, (void*)user);CHKERRQ(ierr);
340     ierr = TaoADMMSetRegularizerHessianRoutine(tao, user->Hz, user->Hz, HessianReg, (void*)user);CHKERRQ(ierr);
341     ierr = TaoADMMSetRegHessianChangeStatus(tao,PETSC_TRUE);CHKERRQ(ierr);
342   } else if (user->reg == 2) {
343     ierr = TaoADMMSetRegularizerObjectiveAndGradientRoutine(tao, RegularizerObjectiveAndGradient2, (void*)user);CHKERRQ(ierr);
344     ierr = MatShift(user->Hz,1);CHKERRQ(ierr);
345     ierr = MatScale(user->Hz,user->lambda);CHKERRQ(ierr);
346     ierr = TaoADMMSetRegularizerHessianRoutine(tao, user->Hz, user->Hz, HessianMisfit, (void*)user);CHKERRQ(ierr);
347     ierr = TaoADMMSetRegHessianChangeStatus(tao,PETSC_TRUE);CHKERRQ(ierr);
348   } else if (user->reg != 3) SETERRQ(PETSC_COMM_WORLD, 1, "Incorrect Reg type"); /* TaoShell case */
349 
350   /* Set type for the misfit solver */
351   ierr = TaoADMMGetMisfitSubsolver(tao, &misfit);CHKERRQ(ierr);
352   ierr = TaoADMMGetRegularizationSubsolver(tao, &reg);CHKERRQ(ierr);
353   ierr = TaoSetType(misfit,TAONLS);CHKERRQ(ierr);
354   if (user->reg == 3) {
355     ierr = TaoSetType(reg,TAOSHELL);CHKERRQ(ierr);
356     ierr = TaoShellSetContext(reg, (void*) user);CHKERRQ(ierr);
357     ierr = TaoShellSetSolve(reg, TaoShellSolve_SoftThreshold);CHKERRQ(ierr);
358   } else {
359     ierr = TaoSetType(reg,TAONLS);CHKERRQ(ierr);
360   }
361   ierr = TaoSetVariableBounds(misfit,user->xlb,user->xub);CHKERRQ(ierr);
362 
363   /* Soft Thresholding solves the ADMM problem with the L1 regularizer lambda*||z||_1 and the x-z=0 constraint */
364   ierr = TaoADMMSetRegularizerCoefficient(tao, user->lambda);CHKERRQ(ierr);
365   ierr = TaoADMMSetRegularizerConstraintJacobian(tao,NULL,NULL,NullJacobian,(void*)user);CHKERRQ(ierr);
366   ierr = TaoADMMSetMinimumSpectralPenalty(tao,user->mumin);CHKERRQ(ierr);
367 
368   ierr = TaoADMMSetConstraintVectorRHS(tao,user->c);CHKERRQ(ierr);
369   ierr = TaoSetFromOptions(tao);CHKERRQ(ierr);
370   ierr = TaoSolve(tao);CHKERRQ(ierr);
371 
372   /* Save x (reconstruction of object) vector to a binary file, which maybe read from Matlab and convert to a 2D image for comparison. */
373   ierr = PetscViewerBinaryOpen(PETSC_COMM_WORLD,resultFile,FILE_MODE_WRITE,&fd);CHKERRQ(ierr);
374   ierr = VecView(user->x,fd);CHKERRQ(ierr);
375   ierr = PetscViewerDestroy(&fd);CHKERRQ(ierr);
376 
377   /* compute the error */
378   ierr = VecAXPY(user->x,-1,user->xGT);CHKERRQ(ierr);
379   ierr = VecNorm(user->x,NORM_2,&v1);CHKERRQ(ierr);
380   ierr = VecNorm(user->xGT,NORM_2,&v2);CHKERRQ(ierr);
381   ierr = PetscPrintf(PETSC_COMM_WORLD, "relative reconstruction error: ||x-xGT||/||xGT|| = %6.4e.\n", (double)(v1/v2));CHKERRQ(ierr);
382 
383   /* Free TAO data structures */
384   ierr = TaoDestroy(&tao);CHKERRQ(ierr);
385   ierr = DestroyContext(user);CHKERRQ(ierr);
386   ierr = PetscFree(user);CHKERRQ(ierr);
387   ierr = PetscFinalize();
388   return ierr;
389 }
390 
391 /*TEST
392 
393    build:
394       requires: !complex !single !__float128 !define(PETSC_USE_64BIT_INDICES)
395 
396    test:
397       suffix: 1
398       localrunfiles: tomographyData_A_b_xGT
399       args:  -lambda 1.e-8 -tao_monitor -tao_type nls -tao_nls_pc_type icc
400 
401    test:
402       suffix: 2
403       localrunfiles: tomographyData_A_b_xGT
404       args:  -reg 2 -lambda 1.e-8 -tao_admm_dual_update update_basic -tao_admm_regularizer_type regularizer_user -tao_max_it 20 -tao_monitor -tao_admm_tolerance_update_factor 1.e-8  -misfit_tao_nls_pc_type icc -misfit_tao_monitor -reg_tao_monitor
405 
406    test:
407       suffix: 3
408       localrunfiles: tomographyData_A_b_xGT
409       args:  -lambda 1.e-8 -tao_admm_dual_update update_basic -tao_admm_regularizer_type regularizer_soft_thresh -tao_max_it 20 -tao_monitor -tao_admm_tolerance_update_factor 1.e-8 -misfit_tao_nls_pc_type icc -misfit_tao_monitor
410 
411    test:
412       suffix: 4
413       localrunfiles: tomographyData_A_b_xGT
414       args:  -lambda 1.e-8 -tao_admm_dual_update update_adaptive -tao_admm_regularizer_type regularizer_soft_thresh -tao_max_it 20 -tao_monitor -misfit_tao_monitor -misfit_tao_nls_pc_type icc
415 
416    test:
417       suffix: 5
418       localrunfiles: tomographyData_A_b_xGT
419       args:  -reg 2 -lambda 1.e-8 -tao_admm_dual_update update_adaptive -tao_admm_regularizer_type regularizer_user -tao_max_it 20 -tao_monitor -tao_admm_tolerance_update_factor 1.e-8 -misfit_tao_monitor -reg_tao_monitor -misfit_tao_nls_pc_type icc
420 
421    test:
422       suffix: 6
423       localrunfiles: tomographyData_A_b_xGT
424       args:  -reg 3 -lambda 1.e-8 -tao_admm_dual_update update_adaptive -tao_admm_regularizer_type regularizer_user -tao_max_it 20 -tao_monitor -tao_admm_tolerance_update_factor 1.e-8 -misfit_tao_monitor -reg_tao_monitor -misfit_tao_nls_pc_type icc
425 
426 TEST*/
427