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 - the matrix function solver context
 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_pre         - print information about the solver before the solve starts
 68: .  -mfn_view_mat         - view the matrix
 69: .  -mfn_view_rhs         - view right hand side vector
 70: .  -mfn_view_solution    - view computed solution vector
 71: -  -mfn_converged_reason - print reason for convergence/divergence, and number of iterations

 73:    Notes:
 74:    The matrix $A$ is specified with `MFNSetOperator()`. The function $f$ is
 75:    specified via the `FN` object obtained with `MFNGetFN()` or set with `MFNSetFN()`.

 77:    All the command-line options listed above admit an optional argument specifying
 78:    the viewer type and options. For instance, use `-mfn_view_mat binary:amatrix.bin`
 79:    to save the matrix to a binary file, or `-mfn_view_solution :sol.m:ascii_matlab`
 80:    to save the solution in a file that can be executed in Matlab.
 81:    See `PetscObjectViewFromOptions()` for more details.

 83:    Level: beginner

 85: .seealso: [](ch:mfn), `MFNCreate()`, `MFNSetUp()`, `MFNDestroy()`, `MFNSetTolerances()`, `MFNSetOperator()`, `MFNSetFN()`
 86: @*/
 87: PetscErrorCode MFNSolve(MFN mfn,Vec b,Vec x)
 88: {
 89:   PetscFunctionBegin;
 92:   PetscCheckSameComm(mfn,1,b,2);
 94:   if (b!=x) PetscCheckSameComm(mfn,1,x,3);
 95:   mfn->transpose_solve = PETSC_FALSE;
 96:   PetscCall(MFNSolve_Private(mfn,b,x));
 97:   PetscFunctionReturn(PETSC_SUCCESS);
 98: }

100: /*@
101:    MFNSolveTranspose - Solves the transpose matrix function problem. Given a vector $b$,
102:    the vector $x = f(A^T)b$ is returned.

104:    Collective

106:    Input Parameters:
107: +  mfn - the matrix function solver context
108: -  b   - the right hand side vector

110:    Output Parameter:
111: .  x   - the solution (this may be the same vector as `b`, then `b` will be
112:          overwritten with the answer)

114:    Notes:
115:    The matrix $A$ is specified with `MFNSetOperator()`. The function $f$ is
116:    specified via the `FN` object obtained with `MFNGetFN()` or set with `MFNSetFN()`.

118:    See available command-line options at `MFNSolve()`.

120:    Developer Notes:
121:    This is currently implemented with an explicit transpose matrix created
122:    with `MatCreateTranspose()`.

124:    Currently there is no conjugate-transpose version.

126:    Level: beginner

128: .seealso: [](ch:mfn), `MFNSolve()`, `MatCreateTranspose()`
129: @*/
130: PetscErrorCode MFNSolveTranspose(MFN mfn,Vec b,Vec x)
131: {
132:   PetscFunctionBegin;
135:   PetscCheckSameComm(mfn,1,b,2);
137:   if (b!=x) PetscCheckSameComm(mfn,1,x,3);
138:   mfn->transpose_solve = PETSC_TRUE;
139:   if (!mfn->AT) PetscCall(MatCreateTranspose(mfn->A,&mfn->AT));
140:   PetscCall(MFNSolve_Private(mfn,b,x));
141:   PetscFunctionReturn(PETSC_SUCCESS);
142: }

144: /*@
145:    MFNGetIterationNumber - Gets the current iteration number. If the
146:    call to `MFNSolve()` is complete, then it returns the number of iterations
147:    carried out by the solution method.

149:    Not Collective

151:    Input Parameter:
152: .  mfn - the matrix function solver context

154:    Output Parameter:
155: .  its - number of iterations

157:    Note:
158:    During the $i$-th iteration this call returns $i-1$. If `MFNSolve()` is
159:    complete, then parameter `its` contains either the iteration number at
160:    which convergence was successfully reached, or failure was detected.
161:    Call `MFNGetConvergedReason()` to determine if the solver converged or
162:    failed and why.

164:    Level: intermediate

166: .seealso: [](ch:mfn), `MFNGetConvergedReason()`, `MFNSetTolerances()`
167: @*/
168: PetscErrorCode MFNGetIterationNumber(MFN mfn,PetscInt *its)
169: {
170:   PetscFunctionBegin;
172:   PetscAssertPointer(its,2);
173:   *its = mfn->its;
174:   PetscFunctionReturn(PETSC_SUCCESS);
175: }

177: /*@
178:    MFNGetConvergedReason - Gets the reason why the `MFNSolve()` iteration was
179:    stopped.

181:    Not Collective

183:    Input Parameter:
184: .  mfn - the matrix function solver context

186:    Output Parameter:
187: .  reason - negative value indicates diverged, positive value converged, see
188:    `MFNConvergedReason` for the possible values

190:    Options Database Key:
191: .  -mfn_converged_reason - print reason for convergence/divergence, and number of iterations

193:    Notes:
194:    If this routine is called before or doing the `MFNSolve()` the value of
195:    `MFN_CONVERGED_ITERATING` is returned.

197:    Basic solvers (e.g., unrestarted Krylov iterations) cannot determine if the
198:    computation is accurate up to the requested tolerance. In that case, the
199:    converged reason is set to `MFN_CONVERGED_ITS` if the requested number of steps
200:    (for instance, the `ncv` value in unrestarted Krylov methods) have been
201:    completed successfully.

203:    Level: intermediate

205: .seealso: [](ch:mfn), `MFNSetTolerances()`, `MFNSolve()`, `MFNConvergedReason`, `MFNSetErrorIfNotConverged()`
206: @*/
207: PetscErrorCode MFNGetConvergedReason(MFN mfn,MFNConvergedReason *reason)
208: {
209:   PetscFunctionBegin;
211:   PetscAssertPointer(reason,2);
212:   *reason = mfn->reason;
213:   PetscFunctionReturn(PETSC_SUCCESS);
214: }