1 static char help[] = "Tests SNESLinesearch handling of Inf/Nan.\n\n"; 2 3 /* 4 Include "petscsnes.h" so that we can use SNES solvers. Note that this 5 file automatically includes: 6 petscsys.h - base PETSc routines petscvec.h - vectors 7 petscmat.h - matrices 8 petscis.h - index sets petscksp.h - Krylov subspace methods 9 petscviewer.h - viewers petscpc.h - preconditioners 10 petscksp.h - linear solvers 11 */ 12 /*F 13 This examples solves 14 \begin{equation} 15 F\genfrac{(}{)}{0pt}{}{x_0}{x_1} = \genfrac{(}{)}{0pt}{}{\sin(3 x_0) + x_0}{x_1} 16 \end{equation} 17 F*/ 18 #include <petscsnes.h> 19 20 /* 21 User-defined routines 22 */ 23 extern PetscErrorCode FormJacobian2(SNES, Vec, Mat, Mat, void *); 24 extern PetscErrorCode FormFunction2(SNES, Vec, Vec, void *); 25 extern PetscErrorCode FormObjective(SNES, Vec, PetscReal *, void *); 26 27 /* 28 This is a very hacking way to trigger the objective function generating an infinity at a particular count to the call FormObjective(). 29 Different line searches evaluate the full step at different counts. For l2 it is the third call (infatcount == 2) while for bt it is the second call. 30 */ 31 PetscInt infatcount = 0; 32 33 int main(int argc, char **argv) 34 { 35 SNES snes; /* nonlinear solver context */ 36 KSP ksp; /* linear solver context */ 37 PC pc; /* preconditioner context */ 38 Vec x, r; /* solution, residual vectors */ 39 Mat J; /* Jacobian matrix */ 40 PetscInt its; 41 PetscMPIInt size; 42 PetscScalar *xx; 43 PetscBool flg; 44 char type[256]; 45 46 PetscFunctionBeginUser; 47 PetscCall(PetscInitialize(&argc, &argv, (char *)0, help)); 48 PetscCall(PetscOptionsGetString(NULL, NULL, "-snes_linesearch_type", type, sizeof(type), &flg)); 49 if (flg) { 50 PetscCall(PetscStrcmp(type, SNESLINESEARCHBT, &flg)); 51 if (flg) infatcount = 1; 52 PetscCall(PetscStrcmp(type, SNESLINESEARCHL2, &flg)); 53 if (flg) infatcount = 2; 54 } 55 56 PetscCallMPI(MPI_Comm_size(PETSC_COMM_WORLD, &size)); 57 PetscCheck(size == 1, PETSC_COMM_WORLD, PETSC_ERR_WRONG_MPI_SIZE, "Example is only for sequential runs"); 58 59 /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 60 Create nonlinear solver context 61 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */ 62 PetscCall(SNESCreate(PETSC_COMM_WORLD, &snes)); 63 64 /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 65 Create matrix and vector data structures; set corresponding routines 66 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */ 67 /* 68 Create vectors for solution and nonlinear function 69 */ 70 PetscCall(VecCreate(PETSC_COMM_WORLD, &x)); 71 PetscCall(VecSetSizes(x, PETSC_DECIDE, 2)); 72 PetscCall(VecSetFromOptions(x)); 73 PetscCall(VecDuplicate(x, &r)); 74 75 /* 76 Create Jacobian matrix data structure 77 */ 78 PetscCall(MatCreate(PETSC_COMM_WORLD, &J)); 79 PetscCall(MatSetSizes(J, PETSC_DECIDE, PETSC_DECIDE, 2, 2)); 80 PetscCall(MatSetFromOptions(J)); 81 PetscCall(MatSetUp(J)); 82 83 PetscCall(SNESSetFunction(snes, r, FormFunction2, NULL)); 84 PetscCall(SNESSetObjective(snes, FormObjective, NULL)); 85 PetscCall(SNESSetJacobian(snes, J, J, FormJacobian2, NULL)); 86 87 /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 88 Customize nonlinear solver; set runtime options 89 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */ 90 /* 91 Set linear solver defaults for this problem. By extracting the 92 KSP and PC contexts from the SNES context, we can then 93 directly call any KSP and PC routines to set various options. 94 */ 95 PetscCall(SNESGetKSP(snes, &ksp)); 96 PetscCall(KSPGetPC(ksp, &pc)); 97 PetscCall(PCSetType(pc, PCNONE)); 98 PetscCall(KSPSetTolerances(ksp, 1.e-4, PETSC_DEFAULT, PETSC_DEFAULT, 20)); 99 100 /* 101 Set SNES/KSP/KSP/PC runtime options, e.g., 102 -snes_view -snes_monitor -ksp_type <ksp> -pc_type <pc> 103 These options will override those specified above as long as 104 SNESSetFromOptions() is called _after_ any other customization 105 routines. 106 */ 107 PetscCall(SNESSetFromOptions(snes)); 108 109 /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 110 Evaluate initial guess; then solve nonlinear system 111 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */ 112 PetscCall(VecGetArray(x, &xx)); 113 xx[0] = 2.0; 114 xx[1] = 3.0; 115 PetscCall(VecRestoreArray(x, &xx)); 116 117 /* 118 Note: The user should initialize the vector, x, with the initial guess 119 for the nonlinear solver prior to calling SNESSolve(). In particular, 120 to employ an initial guess of zero, the user should explicitly set 121 this vector to zero by calling VecSet(). 122 */ 123 124 PetscCall(SNESSolve(snes, NULL, x)); 125 PetscCall(SNESGetIterationNumber(snes, &its)); 126 PetscCall(PetscPrintf(PETSC_COMM_WORLD, "Number of SNES iterations = %" PetscInt_FMT "\n", its)); 127 128 /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 129 Free work space. All PETSc objects should be destroyed when they 130 are no longer needed. 131 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */ 132 133 PetscCall(VecDestroy(&x)); 134 PetscCall(VecDestroy(&r)); 135 PetscCall(MatDestroy(&J)); 136 PetscCall(SNESDestroy(&snes)); 137 PetscCall(PetscFinalize()); 138 return 0; 139 } 140 141 PetscErrorCode FormObjective(SNES snes, Vec x, PetscReal *f, void *dummy) 142 { 143 Vec F; 144 static PetscInt cnt = 0; 145 const PetscReal one = 1.0, zero = 0.0; 146 PetscReal inf; 147 148 PetscFunctionBeginUser; 149 PetscCall(PetscFPTrapPush(PETSC_FP_TRAP_OFF)); 150 inf = one / zero; 151 PetscCall(PetscFPTrapPop()); 152 if (cnt++ == infatcount) *f = inf; 153 else { 154 PetscCall(VecDuplicate(x, &F)); 155 PetscCall(FormFunction2(snes, x, F, dummy)); 156 PetscCall(VecNorm(F, NORM_2, f)); 157 PetscCall(VecDestroy(&F)); 158 *f = (*f) * (*f); 159 } 160 PetscFunctionReturn(PETSC_SUCCESS); 161 } 162 163 PetscErrorCode FormFunction2(SNES snes, Vec x, Vec f, void *dummy) 164 { 165 const PetscScalar *xx; 166 PetscScalar *ff; 167 168 PetscFunctionBeginUser; 169 /* 170 Get pointers to vector data. 171 - For default PETSc vectors, VecGetArray() returns a pointer to 172 the data array. Otherwise, the routine is implementation dependent. 173 - You MUST call VecRestoreArray() when you no longer need access to 174 the array. 175 */ 176 PetscCall(VecGetArrayRead(x, &xx)); 177 PetscCall(VecGetArray(f, &ff)); 178 179 /* 180 Compute function 181 */ 182 ff[0] = PetscSinScalar(3.0 * xx[0]) + xx[0]; 183 ff[1] = xx[1]; 184 185 /* 186 Restore vectors 187 */ 188 PetscCall(VecRestoreArrayRead(x, &xx)); 189 PetscCall(VecRestoreArray(f, &ff)); 190 PetscFunctionReturn(PETSC_SUCCESS); 191 } 192 193 PetscErrorCode FormJacobian2(SNES snes, Vec x, Mat jac, Mat B, void *dummy) 194 { 195 const PetscScalar *xx; 196 PetscScalar A[4]; 197 PetscInt idx[2] = {0, 1}; 198 199 PetscFunctionBeginUser; 200 /* 201 Get pointer to vector data 202 */ 203 PetscCall(VecGetArrayRead(x, &xx)); 204 205 /* 206 Compute Jacobian entries and insert into matrix. 207 - Since this is such a small problem, we set all entries for 208 the matrix at once. 209 */ 210 A[0] = 3.0 * PetscCosScalar(3.0 * xx[0]) + 1.0; 211 A[1] = 0.0; 212 A[2] = 0.0; 213 A[3] = 1.0; 214 PetscCall(MatSetValues(B, 2, idx, 2, idx, A, INSERT_VALUES)); 215 216 /* 217 Restore vector 218 */ 219 PetscCall(VecRestoreArrayRead(x, &xx)); 220 221 /* 222 Assemble matrix 223 */ 224 PetscCall(MatAssemblyBegin(B, MAT_FINAL_ASSEMBLY)); 225 PetscCall(MatAssemblyEnd(B, MAT_FINAL_ASSEMBLY)); 226 if (jac != B) { 227 PetscCall(MatAssemblyBegin(jac, MAT_FINAL_ASSEMBLY)); 228 PetscCall(MatAssemblyEnd(jac, MAT_FINAL_ASSEMBLY)); 229 } 230 PetscFunctionReturn(PETSC_SUCCESS); 231 } 232 233 /*TEST 234 235 test: 236 args: -snes_converged_reason -snes_linesearch_monitor -snes_linesearch_type l2 237 filter: grep Inf 238 239 TEST*/ 240