Date: 2024-12-02T08:57:17+00:00

Actual source code: mfnsolve.c
slepc-3.22.2 2024-12-02
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      1: /*
      2:    - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
      3:    SLEPc - Scalable Library for Eigenvalue Problem Computations
      4:    Copyright (c) 2002-, Universitat Politecnica de Valencia, Spain

      6:    This file is part of SLEPc.
      7:    SLEPc is distributed under a 2-clause BSD license (see LICENSE).
      8:    - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
      9: */
     10: /*
     11:    MFN routines related to the solution process
     12: */

     14: #include <slepc/private/mfnimpl.h>

     16: static PetscErrorCode MFNSolve_Private(MFN mfn,Vec b,Vec x)
     17: {
     18:   PetscFunctionBegin;
     19:   PetscCall(VecSetErrorIfLocked(x,3));

     21:   /* call setup */
     22:   PetscCall(MFNSetUp(mfn));
     23:   mfn->its = 0;

     25:   PetscCall(MFNViewFromOptions(mfn,NULL,"-mfn_view_pre"));

     27:   /* check nonzero right-hand side */
     28:   PetscCall(VecNorm(b,NORM_2,&mfn->bnorm));
     29:   PetscCheck(mfn->bnorm,PetscObjectComm((PetscObject)mfn),PETSC_ERR_ARG_WRONG,"Cannot pass a zero b vector to MFNSolve()");

     31:   /* call solver */
     32:   PetscCall(PetscLogEventBegin(MFN_Solve,mfn,b,x,0));
     33:   if (b!=x) PetscCall(VecLockReadPush(b));
     34:   PetscUseTypeMethod(mfn,solve,b,x);
     35:   if (b!=x) PetscCall(VecLockReadPop(b));
     36:   PetscCall(PetscLogEventEnd(MFN_Solve,mfn,b,x,0));

     38:   PetscCheck(mfn->reason,PetscObjectComm((PetscObject)mfn),PETSC_ERR_PLIB,"Internal error, solver returned without setting converged reason");

     40:   PetscCheck(!mfn->errorifnotconverged || mfn->reason>=0,PetscObjectComm((PetscObject)mfn),PETSC_ERR_NOT_CONVERGED,"MFNSolve has not converged");

     42:   /* various viewers */
     43:   PetscCall(MFNViewFromOptions(mfn,NULL,"-mfn_view"));
     44:   PetscCall(MFNConvergedReasonViewFromOptions(mfn));
     45:   PetscCall(MatViewFromOptions(mfn->A,(PetscObject)mfn,"-mfn_view_mat"));
     46:   PetscCall(VecViewFromOptions(b,(PetscObject)mfn,"-mfn_view_rhs"));
     47:   PetscCall(VecViewFromOptions(x,(PetscObject)mfn,"-mfn_view_solution"));
     48:   PetscFunctionReturn(PETSC_SUCCESS);
     49: }

     51: /*@
     52:    MFNSolve - Solves the matrix function problem. Given a vector b, the
     53:    vector x = f(A)*b is returned.

     55:    Collective

     57:    Input Parameters:
     58: +  mfn - matrix function context obtained from MFNCreate()
     59: -  b   - the right hand side vector

     61:    Output Parameter:
     62: .  x   - the solution (this may be the same vector as b, then b will be
     63:          overwritten with the answer)

     65:    Options Database Keys:
     66: +  -mfn_view - print information about the solver used
     67: .  -mfn_view_mat binary - save the matrix to the default binary viewer
     68: .  -mfn_view_rhs binary - save right hand side vector to the default binary viewer
     69: .  -mfn_view_solution binary - save computed solution vector to the default binary viewer
     70: -  -mfn_converged_reason - print reason for convergence, and number of iterations

     72:    Notes:
     73:    The matrix A is specified with MFNSetOperator().
     74:    The function f is specified with MFNSetFN().

     76:    Level: beginner

     78: .seealso: MFNCreate(), MFNSetUp(), MFNDestroy(), MFNSetTolerances(),
     79:           MFNSetOperator(), MFNSetFN()
     80: @*/
     81: PetscErrorCode MFNSolve(MFN mfn,Vec b,Vec x)
     82: {
     83:   PetscFunctionBegin;
     86:   PetscCheckSameComm(mfn,1,b,2);
     88:   if (b!=x) PetscCheckSameComm(mfn,1,x,3);
     89:   mfn->transpose_solve = PETSC_FALSE;
     90:   PetscCall(MFNSolve_Private(mfn,b,x));
     91:   PetscFunctionReturn(PETSC_SUCCESS);
     92: }

     94: /*@
     95:    MFNSolveTranspose - Solves the transpose matrix function problem. Given a vector b,
     96:    the vector x = f(A^T)*b is returned.

     98:    Collective

    100:    Input Parameters:
    101: +  mfn - matrix function context obtained from MFNCreate()
    102: -  b   - the right hand side vector

    104:    Output Parameter:
    105: .  x   - the solution (this may be the same vector as b, then b will be
    106:          overwritten with the answer)

    108:    Note:
    109:    See available options at MFNSolve().

    111:    Level: beginner

    113: .seealso: MFNSolve()
    114: @*/
    115: PetscErrorCode MFNSolveTranspose(MFN mfn,Vec b,Vec x)
    116: {
    117:   PetscFunctionBegin;
    120:   PetscCheckSameComm(mfn,1,b,2);
    122:   if (b!=x) PetscCheckSameComm(mfn,1,x,3);
    123:   mfn->transpose_solve = PETSC_TRUE;
    124:   if (!mfn->AT) PetscCall(MatCreateTranspose(mfn->A,&mfn->AT));
    125:   PetscCall(MFNSolve_Private(mfn,b,x));
    126:   PetscFunctionReturn(PETSC_SUCCESS);
    127: }

    129: /*@
    130:    MFNGetIterationNumber - Gets the current iteration number. If the
    131:    call to MFNSolve() is complete, then it returns the number of iterations
    132:    carried out by the solution method.

    134:    Not Collective

    136:    Input Parameter:
    137: .  mfn - the matrix function context

    139:    Output Parameter:
    140: .  its - number of iterations

    142:    Note:
    143:    During the i-th iteration this call returns i-1. If MFNSolve() is
    144:    complete, then parameter "its" contains either the iteration number at
    145:    which convergence was successfully reached, or failure was detected.
    146:    Call MFNGetConvergedReason() to determine if the solver converged or
    147:    failed and why.

    149:    Level: intermediate

    151: .seealso: MFNGetConvergedReason(), MFNSetTolerances()
    152: @*/
    153: PetscErrorCode MFNGetIterationNumber(MFN mfn,PetscInt *its)
    154: {
    155:   PetscFunctionBegin;
    157:   PetscAssertPointer(its,2);
    158:   *its = mfn->its;
    159:   PetscFunctionReturn(PETSC_SUCCESS);
    160: }

    162: /*@
    163:    MFNGetConvergedReason - Gets the reason why the MFNSolve() iteration was
    164:    stopped.

    166:    Not Collective

    168:    Input Parameter:
    169: .  mfn - the matrix function context

    171:    Output Parameter:
    172: .  reason - negative value indicates diverged, positive value converged

    174:    Notes:

    176:    Possible values for reason are
    177: +  MFN_CONVERGED_TOL - converged up to tolerance
    178: .  MFN_CONVERGED_ITS - solver completed the requested number of steps
    179: .  MFN_DIVERGED_ITS - required more than max_it iterations to reach convergence
    180: -  MFN_DIVERGED_BREAKDOWN - generic breakdown in method

    182:    Can only be called after the call to MFNSolve() is complete.

    184:    Basic solvers (e.g. unrestarted Krylov iterations) cannot determine if the
    185:    computation is accurate up to the requested tolerance. In that case, the
    186:    converged reason is set to MFN_CONVERGED_ITS if the requested number of steps
    187:    (for instance, the ncv value in unrestarted Krylov methods) have been
    188:    completed successfully.

    190:    Level: intermediate

    192: .seealso: MFNSetTolerances(), MFNSolve(), MFNConvergedReason, MFNSetErrorIfNotConverged()
    193: @*/
    194: PetscErrorCode MFNGetConvergedReason(MFN mfn,MFNConvergedReason *reason)
    195: {
    196:   PetscFunctionBegin;
    198:   PetscAssertPointer(reason,2);
    199:   *reason = mfn->reason;
    200:   PetscFunctionReturn(PETSC_SUCCESS);
    201: }