Date: 2025-03-28T21:11:07+00:00

Actual source code: ksponly.c

      1: #include <petsc/private/snesimpl.h>

      3: typedef struct {
      4:   PetscBool transpose_solve;
      5: } SNES_KSPONLY;

      7: static PetscErrorCode SNESSolve_KSPONLY(SNES snes)
      8: {
      9:   SNES_KSPONLY *ksponly = (SNES_KSPONLY *)snes->data;
     10:   PetscInt      lits;
     11:   Vec           Y, X, F;

     13:   PetscFunctionBegin;
     14:   PetscCheck(!snes->xl && !snes->xu && !snes->ops->computevariablebounds, PetscObjectComm((PetscObject)snes), PETSC_ERR_ARG_WRONGSTATE, "SNES solver %s does not support bounds", ((PetscObject)snes)->type_name);

     16:   snes->numFailures            = 0;
     17:   snes->numLinearSolveFailures = 0;
     18:   snes->reason                 = SNES_CONVERGED_ITERATING;
     19:   snes->iter                   = 0;
     20:   snes->norm                   = 0.0;

     22:   X = snes->vec_sol;
     23:   F = snes->vec_func;
     24:   Y = snes->vec_sol_update;

     26:   if (!snes->vec_func_init_set) {
     27:     PetscCall(SNESComputeFunction(snes, X, F));
     28:   } else snes->vec_func_init_set = PETSC_FALSE;

     30:   if (snes->numbermonitors) {
     31:     PetscReal fnorm;
     32:     PetscCall(VecNorm(F, NORM_2, &fnorm));
     33:     SNESCheckFunctionNorm(snes, fnorm);
     34:     PetscCall(SNESMonitor(snes, 0, fnorm));
     35:   }

     37:   /* Call general purpose update function */
     38:   PetscTryTypeMethod(snes, update, 0);

     40:   /* Solve J Y = F, where J is Jacobian matrix */
     41:   PetscCall(SNESComputeJacobian(snes, X, snes->jacobian, snes->jacobian_pre));

     43:   SNESCheckJacobianDomainerror(snes);

     45:   PetscCall(KSPSetOperators(snes->ksp, snes->jacobian, snes->jacobian_pre));
     46:   if (ksponly->transpose_solve) {
     47:     PetscCall(KSPSolveTranspose(snes->ksp, F, Y));
     48:   } else {
     49:     PetscCall(KSPSolve(snes->ksp, F, Y));
     50:   }
     51:   snes->reason = SNES_CONVERGED_ITS;
     52:   SNESCheckKSPSolve(snes);

     54:   PetscCall(KSPGetIterationNumber(snes->ksp, &lits));
     55:   PetscCall(PetscInfo(snes, "iter=%" PetscInt_FMT ", linear solve iterations=%" PetscInt_FMT "\n", snes->iter, lits));
     56:   snes->iter++;

     58:   /* Take the computed step. */
     59:   PetscCall(VecAXPY(X, -1.0, Y));
     60:   if (snes->numbermonitors) {
     61:     PetscReal fnorm;
     62:     PetscCall(SNESComputeFunction(snes, X, F));
     63:     PetscCall(VecNorm(F, NORM_2, &fnorm));
     64:     SNESCheckFunctionNorm(snes, fnorm);
     65:     PetscCall(SNESMonitor(snes, 1, fnorm));
     66:   }
     67:   PetscFunctionReturn(PETSC_SUCCESS);
     68: }

     70: static PetscErrorCode SNESSetUp_KSPONLY(SNES snes)
     71: {
     72:   PetscFunctionBegin;
     73:   PetscCall(SNESSetUpMatrices(snes));
     74:   PetscFunctionReturn(PETSC_SUCCESS);
     75: }

     77: static PetscErrorCode SNESDestroy_KSPONLY(SNES snes)
     78: {
     79:   PetscFunctionBegin;
     80:   PetscCall(PetscFree(snes->data));
     81:   PetscFunctionReturn(PETSC_SUCCESS);
     82: }

     84: /*MC
     85:    SNESKSPONLY - Nonlinear solver that performs one Newton step with `KSPSolve()` and does not compute any norms.

     87:    Level: beginner

     89:    Note:
     90:    The main purpose of this solver is to solve linear problems using the `SNES` interface, without
     91:    any additional overhead in the form of vector norm operations.

     93: .seealso: [](ch_snes), `SNES`, `SNESType`, `SNESCreate()`, `SNES`, `SNESSetType()`, `SNESNEWTONLS`, `SNESNEWTONTR`, `SNESKSPTRANSPOSEONLY`
     94: M*/
     95: PETSC_EXTERN PetscErrorCode SNESCreate_KSPONLY(SNES snes)
     96: {
     97:   SNES_KSPONLY *ksponly;

     99:   PetscFunctionBegin;
    100:   snes->ops->setup          = SNESSetUp_KSPONLY;
    101:   snes->ops->solve          = SNESSolve_KSPONLY;
    102:   snes->ops->destroy        = SNESDestroy_KSPONLY;
    103:   snes->ops->setfromoptions = NULL;
    104:   snes->ops->view           = NULL;
    105:   snes->ops->reset          = NULL;

    107:   snes->usesksp = PETSC_TRUE;
    108:   snes->usesnpc = PETSC_FALSE;

    110:   snes->alwayscomputesfinalresidual = PETSC_FALSE;

    112:   PetscCall(SNESParametersInitialize(snes));

    114:   PetscCall(PetscNew(&ksponly));
    115:   snes->data = (void *)ksponly;
    116:   PetscFunctionReturn(PETSC_SUCCESS);
    117: }

    119: /*MC
    120:    SNESKSPTRANSPOSEONLY - Nonlinear solver that performs one Newton step with `KSPSolveTranspose()` and does not compute any norms.

    122:    Level: beginner

    124:    Note:
    125:    The main purpose of this solver is to solve transposed linear problems using the `SNES` interface, without
    126:    any additional overhead in the form of vector operations within adjoint solvers.

    128: .seealso: [](ch_snes), `SNES`, `SNESType`, `SNESCreate()`, `SNES`, `SNESSetType()`, `SNESKS`, `SNESNEWTONLS`, `SNESNEWTONTR`
    129: M*/
    130: PETSC_EXTERN PetscErrorCode SNESCreate_KSPTRANSPOSEONLY(SNES snes)
    131: {
    132:   SNES_KSPONLY *kspo;

    134:   PetscFunctionBegin;
    135:   PetscCall(SNESCreate_KSPONLY(snes));
    136:   PetscCall(PetscObjectChangeTypeName((PetscObject)snes, SNESKSPTRANSPOSEONLY));
    137:   kspo                  = (SNES_KSPONLY *)snes->data;
    138:   kspo->transpose_solve = PETSC_TRUE;
    139:   PetscFunctionReturn(PETSC_SUCCESS);
    140: }