1 2 static char help[] = "Tests TSLINESEARCHL2 handing of Inf/Nan.\n\n"; 3 4 /* 5 Include "petscsnes.h" so that we can use SNES solvers. Note that this 6 file automatically includes: 7 petscsys.h - base PETSc routines petscvec.h - vectors 8 petscmat.h - matrices 9 petscis.h - index sets petscksp.h - Krylov subspace methods 10 petscviewer.h - viewers petscpc.h - preconditioners 11 petscksp.h - linear solvers 12 */ 13 /*F 14 This examples solves either 15 \begin{equation} 16 F\genfrac{(}{)}{0pt}{}{x_0}{x_1} = \genfrac{(}{)}{0pt}{}{\sin(3 x_0) + x_0}{x_1} 17 \end{equation} 18 F*/ 19 #include <petscsnes.h> 20 21 /* 22 User-defined routines 23 */ 24 extern PetscErrorCode FormJacobian2(SNES, Vec, Mat, Mat, void *); 25 extern PetscErrorCode FormFunction2(SNES, Vec, Vec, void *); 26 extern PetscErrorCode FormObjective(SNES, Vec, PetscReal *, void *); 27 28 /* 29 This is a very hacking way to trigger the objective function generating an infinity at a particular count to the call FormObjective(). 30 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. 31 */ 32 PetscInt infatcount = 0; 33 34 int main(int argc, char **argv) { 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 Vec F; 143 static PetscInt cnt = 0; 144 145 if (cnt++ == infatcount) *f = INFINITY; 146 else { 147 PetscCall(VecDuplicate(x, &F)); 148 PetscCall(FormFunction2(snes, x, F, dummy)); 149 PetscCall(VecNorm(F, NORM_2, f)); 150 PetscCall(VecDestroy(&F)); 151 *f = (*f) * (*f); 152 } 153 return 0; 154 } 155 156 PetscErrorCode FormFunction2(SNES snes, Vec x, Vec f, void *dummy) { 157 const PetscScalar *xx; 158 PetscScalar *ff; 159 160 /* 161 Get pointers to vector data. 162 - For default PETSc vectors, VecGetArray() returns a pointer to 163 the data array. Otherwise, the routine is implementation dependent. 164 - You MUST call VecRestoreArray() when you no longer need access to 165 the array. 166 */ 167 PetscCall(VecGetArrayRead(x, &xx)); 168 PetscCall(VecGetArray(f, &ff)); 169 170 /* 171 Compute function 172 */ 173 ff[0] = PetscSinScalar(3.0 * xx[0]) + xx[0]; 174 ff[1] = xx[1]; 175 176 /* 177 Restore vectors 178 */ 179 PetscCall(VecRestoreArrayRead(x, &xx)); 180 PetscCall(VecRestoreArray(f, &ff)); 181 return 0; 182 } 183 184 PetscErrorCode FormJacobian2(SNES snes, Vec x, Mat jac, Mat B, void *dummy) { 185 const PetscScalar *xx; 186 PetscScalar A[4]; 187 PetscInt idx[2] = {0, 1}; 188 189 /* 190 Get pointer to vector data 191 */ 192 PetscCall(VecGetArrayRead(x, &xx)); 193 194 /* 195 Compute Jacobian entries and insert into matrix. 196 - Since this is such a small problem, we set all entries for 197 the matrix at once. 198 */ 199 A[0] = 3.0 * PetscCosScalar(3.0 * xx[0]) + 1.0; 200 A[1] = 0.0; 201 A[2] = 0.0; 202 A[3] = 1.0; 203 PetscCall(MatSetValues(B, 2, idx, 2, idx, A, INSERT_VALUES)); 204 205 /* 206 Restore vector 207 */ 208 PetscCall(VecRestoreArrayRead(x, &xx)); 209 210 /* 211 Assemble matrix 212 */ 213 PetscCall(MatAssemblyBegin(B, MAT_FINAL_ASSEMBLY)); 214 PetscCall(MatAssemblyEnd(B, MAT_FINAL_ASSEMBLY)); 215 if (jac != B) { 216 PetscCall(MatAssemblyBegin(jac, MAT_FINAL_ASSEMBLY)); 217 PetscCall(MatAssemblyEnd(jac, MAT_FINAL_ASSEMBLY)); 218 } 219 return 0; 220 } 221 222 /*TEST 223 224 build: 225 requires: infinity 226 227 test: 228 args: -snes_converged_reason -snes_linesearch_monitor -snes_linesearch_type l2 229 filter: grep Inf 230 231 TEST*/ 232