1 static char help[] = "Newton method to solve u'' + u^{2} = f, sequentially.\n\ 2 This example employs a user-defined reasonview routine.\n\n"; 3 4 #include <petscsnes.h> 5 6 /* 7 User-defined routines 8 */ 9 PETSC_EXTERN PetscErrorCode FormJacobian(SNES, Vec, Mat, Mat, void *); 10 PETSC_EXTERN PetscErrorCode FormFunction(SNES, Vec, Vec, void *); 11 PETSC_EXTERN PetscErrorCode FormInitialGuess(Vec); 12 PETSC_EXTERN PetscErrorCode MySNESConvergedReasonView(SNES, void *); 13 PETSC_EXTERN PetscErrorCode MyKSPConvergedReasonView(KSP, void *); 14 15 /* 16 User-defined context for monitoring 17 */ 18 typedef struct { 19 PetscViewer viewer; 20 } ReasonViewCtx; 21 22 int main(int argc, char **argv) 23 { 24 SNES snes; /* SNES context */ 25 KSP ksp; /* KSP context */ 26 Vec x, r, F, U; /* vectors */ 27 Mat J; /* Jacobian matrix */ 28 ReasonViewCtx monP; /* monitoring context */ 29 PetscInt its, n = 5, i; 30 PetscMPIInt size; 31 PetscScalar h, xp, v; 32 MPI_Comm comm; 33 34 PetscFunctionBeginUser; 35 PetscCall(PetscInitialize(&argc, &argv, (char *)0, help)); 36 PetscCallMPI(MPI_Comm_size(PETSC_COMM_WORLD, &size)); 37 PetscCheck(size == 1, PETSC_COMM_SELF, PETSC_ERR_WRONG_MPI_SIZE, "This is a uniprocessor example only!"); 38 PetscCall(PetscOptionsGetInt(NULL, NULL, "-n", &n, NULL)); 39 h = 1.0 / (n - 1); 40 comm = PETSC_COMM_WORLD; 41 /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 42 Create nonlinear solver context 43 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */ 44 45 PetscCall(SNESCreate(comm, &snes)); 46 47 /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 48 Create vector data structures; set function evaluation routine 49 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */ 50 /* 51 Note that we form 1 vector from scratch and then duplicate as needed. 52 */ 53 PetscCall(VecCreate(comm, &x)); 54 PetscCall(VecSetSizes(x, PETSC_DECIDE, n)); 55 PetscCall(VecSetFromOptions(x)); 56 PetscCall(VecDuplicate(x, &r)); 57 PetscCall(VecDuplicate(x, &F)); 58 PetscCall(VecDuplicate(x, &U)); 59 60 /* 61 Set function evaluation routine and vector 62 */ 63 PetscCall(SNESSetFunction(snes, r, FormFunction, (void *)F)); 64 65 /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 66 Create matrix data structure; set Jacobian evaluation routine 67 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */ 68 69 PetscCall(MatCreate(comm, &J)); 70 PetscCall(MatSetSizes(J, PETSC_DECIDE, PETSC_DECIDE, n, n)); 71 PetscCall(MatSetFromOptions(J)); 72 PetscCall(MatSeqAIJSetPreallocation(J, 3, NULL)); 73 74 /* 75 Set Jacobian matrix data structure and default Jacobian evaluation 76 routine. User can override with: 77 -snes_fd : default finite differencing approximation of Jacobian 78 -snes_mf : matrix-free Newton-Krylov method with no preconditioning 79 (unless user explicitly sets preconditioner) 80 -snes_mf_operator : form preconditioning matrix as set by the user, 81 but use matrix-free approx for Jacobian-vector 82 products within Newton-Krylov method 83 */ 84 85 PetscCall(SNESSetJacobian(snes, J, J, FormJacobian, NULL)); 86 87 /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 88 Customize nonlinear solver; set runtime options 89 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */ 90 91 /* 92 Set an optional user-defined reasonview routine 93 */ 94 PetscCall(PetscViewerASCIIGetStdout(comm, &monP.viewer)); 95 /* Just make sure we can not repeat adding the same function 96 * PETSc will be able to ignore the repeated function 97 */ 98 for (i = 0; i < 4; i++) PetscCall(SNESConvergedReasonViewSet(snes, MySNESConvergedReasonView, &monP, 0)); 99 PetscCall(SNESGetKSP(snes, &ksp)); 100 /* Just make sure we can not repeat adding the same function 101 * PETSc will be able to ignore the repeated function 102 */ 103 for (i = 0; i < 4; i++) PetscCall(KSPConvergedReasonViewSet(ksp, MyKSPConvergedReasonView, &monP, 0)); 104 /* 105 Set SNES/KSP/KSP/PC runtime options, e.g., 106 -snes_view -snes_monitor -ksp_type <ksp> -pc_type <pc> 107 */ 108 PetscCall(SNESSetFromOptions(snes)); 109 110 /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 111 Initialize application: 112 Store right-hand-side of PDE and exact solution 113 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */ 114 115 xp = 0.0; 116 for (i = 0; i < n; i++) { 117 v = 6.0 * xp + PetscPowScalar(xp + 1.e-12, 6.0); /* +1.e-12 is to prevent 0^6 */ 118 PetscCall(VecSetValues(F, 1, &i, &v, INSERT_VALUES)); 119 v = xp * xp * xp; 120 PetscCall(VecSetValues(U, 1, &i, &v, INSERT_VALUES)); 121 xp += h; 122 } 123 124 /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 125 Evaluate initial guess; then solve nonlinear system 126 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */ 127 /* 128 Note: The user should initialize the vector, x, with the initial guess 129 for the nonlinear solver prior to calling SNESSolve(). In particular, 130 to employ an initial guess of zero, the user should explicitly set 131 this vector to zero by calling VecSet(). 132 */ 133 PetscCall(FormInitialGuess(x)); 134 PetscCall(SNESSolve(snes, NULL, x)); 135 PetscCall(SNESGetIterationNumber(snes, &its)); 136 137 /* 138 Free work space. All PETSc objects should be destroyed when they 139 are no longer needed. 140 */ 141 PetscCall(VecDestroy(&x)); 142 PetscCall(VecDestroy(&r)); 143 PetscCall(VecDestroy(&U)); 144 PetscCall(VecDestroy(&F)); 145 PetscCall(MatDestroy(&J)); 146 PetscCall(SNESDestroy(&snes)); 147 PetscCall(PetscFinalize()); 148 return 0; 149 } 150 151 /* 152 FormInitialGuess - Computes initial guess. 153 154 Input/Output Parameter: 155 . x - the solution vector 156 */ 157 PetscErrorCode FormInitialGuess(Vec x) 158 { 159 PetscScalar pfive = .50; 160 161 PetscFunctionBeginUser; 162 PetscCall(VecSet(x, pfive)); 163 PetscFunctionReturn(PETSC_SUCCESS); 164 } 165 166 /* 167 FormFunction - Evaluates nonlinear function, F(x). 168 169 Input Parameters: 170 . snes - the SNES context 171 . x - input vector 172 . ctx - optional user-defined context, as set by SNESSetFunction() 173 174 Output Parameter: 175 . f - function vector 176 177 Note: 178 The user-defined context can contain any application-specific data 179 needed for the function evaluation (such as various parameters, work 180 vectors, and grid information). In this program the context is just 181 a vector containing the right-hand-side of the discretized PDE. 182 */ 183 184 PetscErrorCode FormFunction(SNES snes, Vec x, Vec f, void *ctx) 185 { 186 Vec g = (Vec)ctx; 187 const PetscScalar *xx, *gg; 188 PetscScalar *ff, d; 189 PetscInt i, n; 190 191 PetscFunctionBeginUser; 192 /* 193 Get pointers to vector data. 194 - For default PETSc vectors, VecGetArray() returns a pointer to 195 the data array. Otherwise, the routine is implementation dependent. 196 - You MUST call VecRestoreArray() when you no longer need access to 197 the array. 198 */ 199 PetscCall(VecGetArrayRead(x, &xx)); 200 PetscCall(VecGetArray(f, &ff)); 201 PetscCall(VecGetArrayRead(g, &gg)); 202 203 /* 204 Compute function 205 */ 206 PetscCall(VecGetSize(x, &n)); 207 d = (PetscReal)(n - 1); 208 d = d * d; 209 ff[0] = xx[0]; 210 for (i = 1; i < n - 1; i++) ff[i] = d * (xx[i - 1] - 2.0 * xx[i] + xx[i + 1]) + xx[i] * xx[i] - gg[i]; 211 ff[n - 1] = xx[n - 1] - 1.0; 212 213 /* 214 Restore vectors 215 */ 216 PetscCall(VecRestoreArrayRead(x, &xx)); 217 PetscCall(VecRestoreArray(f, &ff)); 218 PetscCall(VecRestoreArrayRead(g, &gg)); 219 PetscFunctionReturn(PETSC_SUCCESS); 220 } 221 /* ------------------------------------------------------------------- */ 222 /* 223 FormJacobian - Evaluates Jacobian matrix. 224 225 Input Parameters: 226 . snes - the SNES context 227 . x - input vector 228 . dummy - optional user-defined context (not used here) 229 230 Output Parameters: 231 . jac - Jacobian matrix 232 . B - optionally different preconditioning matrix 233 234 */ 235 236 PetscErrorCode FormJacobian(SNES snes, Vec x, Mat jac, Mat B, void *dummy) 237 { 238 const PetscScalar *xx; 239 PetscScalar A[3], d; 240 PetscInt i, n, j[3]; 241 242 PetscFunctionBeginUser; 243 /* 244 Get pointer to vector data 245 */ 246 PetscCall(VecGetArrayRead(x, &xx)); 247 248 /* 249 Compute Jacobian entries and insert into matrix. 250 - Note that in this case we set all elements for a particular 251 row at once. 252 */ 253 PetscCall(VecGetSize(x, &n)); 254 d = (PetscReal)(n - 1); 255 d = d * d; 256 257 /* 258 Interior grid points 259 */ 260 for (i = 1; i < n - 1; i++) { 261 j[0] = i - 1; 262 j[1] = i; 263 j[2] = i + 1; 264 A[0] = A[2] = d; 265 A[1] = -2.0 * d + 2.0 * xx[i]; 266 PetscCall(MatSetValues(B, 1, &i, 3, j, A, INSERT_VALUES)); 267 } 268 269 /* 270 Boundary points 271 */ 272 i = 0; 273 A[0] = 1.0; 274 275 PetscCall(MatSetValues(B, 1, &i, 1, &i, A, INSERT_VALUES)); 276 277 i = n - 1; 278 A[0] = 1.0; 279 280 PetscCall(MatSetValues(B, 1, &i, 1, &i, A, INSERT_VALUES)); 281 282 /* 283 Restore vector 284 */ 285 PetscCall(VecRestoreArrayRead(x, &xx)); 286 287 /* 288 Assemble matrix 289 */ 290 PetscCall(MatAssemblyBegin(B, MAT_FINAL_ASSEMBLY)); 291 PetscCall(MatAssemblyEnd(B, MAT_FINAL_ASSEMBLY)); 292 if (jac != B) { 293 PetscCall(MatAssemblyBegin(jac, MAT_FINAL_ASSEMBLY)); 294 PetscCall(MatAssemblyEnd(jac, MAT_FINAL_ASSEMBLY)); 295 } 296 PetscFunctionReturn(PETSC_SUCCESS); 297 } 298 299 PetscErrorCode MySNESConvergedReasonView(SNES snes, void *ctx) 300 { 301 ReasonViewCtx *monP = (ReasonViewCtx *)ctx; 302 PetscViewer viewer = monP->viewer; 303 SNESConvergedReason reason; 304 const char *strreason; 305 306 PetscFunctionBeginUser; 307 PetscCall(SNESGetConvergedReason(snes, &reason)); 308 PetscCall(SNESGetConvergedReasonString(snes, &strreason)); 309 PetscCall(PetscViewerASCIIPrintf(viewer, "Customized SNES converged reason view\n")); 310 PetscCall(PetscViewerASCIIAddTab(viewer, 1)); 311 if (reason > 0) { 312 PetscCall(PetscViewerASCIIPrintf(viewer, "Converged due to %s\n", strreason)); 313 } else if (reason <= 0) { 314 PetscCall(PetscViewerASCIIPrintf(viewer, "Did not converge due to %s\n", strreason)); 315 } 316 PetscCall(PetscViewerASCIISubtractTab(viewer, 1)); 317 PetscFunctionReturn(PETSC_SUCCESS); 318 } 319 320 PetscErrorCode MyKSPConvergedReasonView(KSP ksp, void *ctx) 321 { 322 ReasonViewCtx *monP = (ReasonViewCtx *)ctx; 323 PetscViewer viewer = monP->viewer; 324 KSPConvergedReason reason; 325 const char *reasonstr; 326 327 PetscFunctionBeginUser; 328 PetscCall(KSPGetConvergedReason(ksp, &reason)); 329 PetscCall(KSPGetConvergedReasonString(ksp, &reasonstr)); 330 PetscCall(PetscViewerASCIIAddTab(viewer, 2)); 331 PetscCall(PetscViewerASCIIPrintf(viewer, "Customized KSP converged reason view\n")); 332 PetscCall(PetscViewerASCIIAddTab(viewer, 1)); 333 if (reason > 0) { 334 PetscCall(PetscViewerASCIIPrintf(viewer, "Converged due to %s\n", reasonstr)); 335 } else if (reason <= 0) { 336 PetscCall(PetscViewerASCIIPrintf(viewer, "Did not converge due to %s\n", reasonstr)); 337 } 338 PetscCall(PetscViewerASCIISubtractTab(viewer, 3)); 339 PetscFunctionReturn(PETSC_SUCCESS); 340 } 341 342 /*TEST 343 344 test: 345 suffix: 1 346 nsize: 1 347 filter: sed -e "s/CONVERGED_ATOL/CONVERGED_RTOL/g" 348 349 test: 350 suffix: 2 351 nsize: 1 352 args: -ksp_converged_reason_view_cancel 353 filter: sed -e "s/CONVERGED_ATOL/CONVERGED_RTOL/g" 354 355 test: 356 suffix: 3 357 nsize: 1 358 args: -ksp_converged_reason_view_cancel -ksp_converged_reason 359 filter: sed -e "s/CONVERGED_ATOL/CONVERGED_RTOL/g" 360 361 test: 362 suffix: 4 363 nsize: 1 364 args: -snes_converged_reason_view_cancel 365 filter: sed -e "s/CONVERGED_ATOL/CONVERGED_RTOL/g" 366 367 test: 368 suffix: 5 369 nsize: 1 370 args: -snes_converged_reason_view_cancel -snes_converged_reason 371 filter: sed -e "s/CONVERGED_ATOL/CONVERGED_RTOL/g" 372 373 TEST*/ 374