xref: /petsc/src/ksp/pc/impls/shell/shellpc.c (revision 4dfa11a44d5adf2389f1d3acbc8f3c1116dc6c3a)

/*
   This provides a simple shell for Fortran (and C programmers) to
  create their own preconditioner without writing much interface code.
*/

#include <petsc/private/pcimpl.h> /*I "petscpc.h" I*/

typedef struct {
  void *ctx; /* user provided contexts for preconditioner */

  PetscErrorCode (*destroy)(PC);
  PetscErrorCode (*setup)(PC);
  PetscErrorCode (*apply)(PC, Vec, Vec);
  PetscErrorCode (*matapply)(PC, Mat, Mat);
  PetscErrorCode (*applysymmetricleft)(PC, Vec, Vec);
  PetscErrorCode (*applysymmetricright)(PC, Vec, Vec);
  PetscErrorCode (*applyBA)(PC, PCSide, Vec, Vec, Vec);
  PetscErrorCode (*presolve)(PC, KSP, Vec, Vec);
  PetscErrorCode (*postsolve)(PC, KSP, Vec, Vec);
  PetscErrorCode (*view)(PC, PetscViewer);
  PetscErrorCode (*applytranspose)(PC, Vec, Vec);
  PetscErrorCode (*applyrich)(PC, Vec, Vec, Vec, PetscReal, PetscReal, PetscReal, PetscInt, PetscBool, PetscInt *, PCRichardsonConvergedReason *);

  char *name;
} PC_Shell;

/*@C
    PCShellGetContext - Returns the user-provided context associated with a shell `PC`

    Not Collective

    Input Parameter:
.   pc - of type `PCSHELL` created with `PCSetType`(pc,shell)

    Output Parameter:
.   ctx - the user provided context

    Level: advanced

    Note:
    This routine is intended for use within various shell routines

   Fortran Note:
    To use this from Fortran you must write a Fortran interface definition for this
    function that tells Fortran the Fortran derived data type that you are passing in as the ctx argument.

.seealso: `PCSHELL`, `PCShellSetContext()`
@*/
PetscErrorCode PCShellGetContext(PC pc, void *ctx) {
  PetscBool flg;

  PetscFunctionBegin;
  PetscValidHeaderSpecific(pc, PC_CLASSID, 1);
  PetscValidPointer(ctx, 2);
  PetscCall(PetscObjectTypeCompare((PetscObject)pc, PCSHELL, &flg));
  if (!flg) *(void **)ctx = NULL;
  else *(void **)ctx = ((PC_Shell *)(pc->data))->ctx;
  PetscFunctionReturn(0);
}

/*@
    PCShellSetContext - sets the context for a shell `PC`

   Logically Collective on pc

    Input Parameters:
+   pc - the `PC` of type `PCSHELL`
-   ctx - the context

   Level: advanced

   Fortran Note:
    To use this from Fortran you must write a Fortran interface definition for this
    function that tells Fortran the Fortran derived data type that you are passing in as the ctx argument.

.seealso: `PCShellGetContext()`, `PCSHELL`
@*/
PetscErrorCode PCShellSetContext(PC pc, void *ctx) {
  PC_Shell *shell = (PC_Shell *)pc->data;
  PetscBool flg;

  PetscFunctionBegin;
  PetscValidHeaderSpecific(pc, PC_CLASSID, 1);
  PetscCall(PetscObjectTypeCompare((PetscObject)pc, PCSHELL, &flg));
  if (flg) shell->ctx = ctx;
  PetscFunctionReturn(0);
}

static PetscErrorCode PCSetUp_Shell(PC pc) {
  PC_Shell *shell = (PC_Shell *)pc->data;

  PetscFunctionBegin;
  PetscCheck(shell->setup, PetscObjectComm((PetscObject)pc), PETSC_ERR_USER, "No setup() routine provided to Shell PC");
  PetscCallBack("PCSHELL callback setup", (*shell->setup)(pc));
  PetscFunctionReturn(0);
}

static PetscErrorCode PCApply_Shell(PC pc, Vec x, Vec y) {
  PC_Shell        *shell = (PC_Shell *)pc->data;
  PetscObjectState instate, outstate;

  PetscFunctionBegin;
  PetscCheck(shell->apply, PetscObjectComm((PetscObject)pc), PETSC_ERR_USER, "No apply() routine provided to Shell PC");
  PetscCall(PetscObjectStateGet((PetscObject)y, &instate));
  PetscCallBack("PCSHELL callback apply", (*shell->apply)(pc, x, y));
  PetscCall(PetscObjectStateGet((PetscObject)y, &outstate));
  /* increase the state of the output vector if the user did not update its state themself as should have been done */
  if (instate == outstate) PetscCall(PetscObjectStateIncrease((PetscObject)y));
  PetscFunctionReturn(0);
}

static PetscErrorCode PCMatApply_Shell(PC pc, Mat X, Mat Y) {
  PC_Shell        *shell = (PC_Shell *)pc->data;
  PetscObjectState instate, outstate;

  PetscFunctionBegin;
  PetscCheck(shell->matapply, PetscObjectComm((PetscObject)pc), PETSC_ERR_USER, "No apply() routine provided to Shell PC");
  PetscCall(PetscObjectStateGet((PetscObject)Y, &instate));
  PetscCallBack("PCSHELL callback apply", (*shell->matapply)(pc, X, Y));
  PetscCall(PetscObjectStateGet((PetscObject)Y, &outstate));
  /* increase the state of the output vector if the user did not update its state themself as should have been done */
  if (instate == outstate) PetscCall(PetscObjectStateIncrease((PetscObject)Y));
  PetscFunctionReturn(0);
}

static PetscErrorCode PCApplySymmetricLeft_Shell(PC pc, Vec x, Vec y) {
  PC_Shell *shell = (PC_Shell *)pc->data;

  PetscFunctionBegin;
  PetscCheck(shell->applysymmetricleft, PetscObjectComm((PetscObject)pc), PETSC_ERR_USER, "No apply() routine provided to Shell PC");
  PetscCallBack("PCSHELL callback apply symmetric left", (*shell->applysymmetricleft)(pc, x, y));
  PetscFunctionReturn(0);
}

static PetscErrorCode PCApplySymmetricRight_Shell(PC pc, Vec x, Vec y) {
  PC_Shell *shell = (PC_Shell *)pc->data;

  PetscFunctionBegin;
  PetscCheck(shell->applysymmetricright, PetscObjectComm((PetscObject)pc), PETSC_ERR_USER, "No apply() routine provided to Shell PC");
  PetscCallBack("PCSHELL callback apply symmetric right", (*shell->applysymmetricright)(pc, x, y));
  PetscFunctionReturn(0);
}

static PetscErrorCode PCApplyBA_Shell(PC pc, PCSide side, Vec x, Vec y, Vec w) {
  PC_Shell        *shell = (PC_Shell *)pc->data;
  PetscObjectState instate, outstate;

  PetscFunctionBegin;
  PetscCheck(shell->applyBA, PetscObjectComm((PetscObject)pc), PETSC_ERR_USER, "No applyBA() routine provided to Shell PC");
  PetscCall(PetscObjectStateGet((PetscObject)w, &instate));
  PetscCallBack("PCSHELL callback applyBA", (*shell->applyBA)(pc, side, x, y, w));
  PetscCall(PetscObjectStateGet((PetscObject)w, &outstate));
  /* increase the state of the output vector if the user did not update its state themself as should have been done */
  if (instate == outstate) PetscCall(PetscObjectStateIncrease((PetscObject)w));
  PetscFunctionReturn(0);
}

static PetscErrorCode PCPreSolveChangeRHS_Shell(PC pc, PetscBool *change) {
  PetscFunctionBegin;
  *change = PETSC_TRUE;
  PetscFunctionReturn(0);
}

static PetscErrorCode PCPreSolve_Shell(PC pc, KSP ksp, Vec b, Vec x) {
  PC_Shell *shell = (PC_Shell *)pc->data;

  PetscFunctionBegin;
  PetscCheck(shell->presolve, PetscObjectComm((PetscObject)pc), PETSC_ERR_USER, "No presolve() routine provided to Shell PC");
  PetscCallBack("PCSHELL callback presolve", (*shell->presolve)(pc, ksp, b, x));
  PetscFunctionReturn(0);
}

static PetscErrorCode PCPostSolve_Shell(PC pc, KSP ksp, Vec b, Vec x) {
  PC_Shell *shell = (PC_Shell *)pc->data;

  PetscFunctionBegin;
  PetscCheck(shell->postsolve, PetscObjectComm((PetscObject)pc), PETSC_ERR_USER, "No postsolve() routine provided to Shell PC");
  PetscCallBack("PCSHELL callback postsolve()", (*shell->postsolve)(pc, ksp, b, x));
  PetscFunctionReturn(0);
}

static PetscErrorCode PCApplyTranspose_Shell(PC pc, Vec x, Vec y) {
  PC_Shell        *shell = (PC_Shell *)pc->data;
  PetscObjectState instate, outstate;

  PetscFunctionBegin;
  PetscCheck(shell->applytranspose, PetscObjectComm((PetscObject)pc), PETSC_ERR_USER, "No applytranspose() routine provided to Shell PC");
  PetscCall(PetscObjectStateGet((PetscObject)y, &instate));
  PetscCallBack("PCSHELL callback applytranspose", (*shell->applytranspose)(pc, x, y));
  PetscCall(PetscObjectStateGet((PetscObject)y, &outstate));
  /* increase the state of the output vector if the user did not update its state themself as should have been done */
  if (instate == outstate) PetscCall(PetscObjectStateIncrease((PetscObject)y));
  PetscFunctionReturn(0);
}

static PetscErrorCode PCApplyRichardson_Shell(PC pc, Vec x, Vec y, Vec w, PetscReal rtol, PetscReal abstol, PetscReal dtol, PetscInt it, PetscBool guesszero, PetscInt *outits, PCRichardsonConvergedReason *reason) {
  PC_Shell        *shell = (PC_Shell *)pc->data;
  PetscObjectState instate, outstate;

  PetscFunctionBegin;
  PetscCheck(shell->applyrich, PetscObjectComm((PetscObject)pc), PETSC_ERR_USER, "No applyrichardson() routine provided to Shell PC");
  PetscCall(PetscObjectStateGet((PetscObject)y, &instate));
  PetscCallBack("PCSHELL callback applyrichardson", (*shell->applyrich)(pc, x, y, w, rtol, abstol, dtol, it, guesszero, outits, reason));
  PetscCall(PetscObjectStateGet((PetscObject)y, &outstate));
  /* increase the state of the output vector since the user did not update its state themself as should have been done */
  if (instate == outstate) PetscCall(PetscObjectStateIncrease((PetscObject)y));
  PetscFunctionReturn(0);
}

static PetscErrorCode PCDestroy_Shell(PC pc) {
  PC_Shell *shell = (PC_Shell *)pc->data;

  PetscFunctionBegin;
  PetscCall(PetscFree(shell->name));
  if (shell->destroy) PetscCallBack("PCSHELL callback destroy", (*shell->destroy)(pc));
  PetscCall(PetscObjectComposeFunction((PetscObject)pc, "PCShellSetDestroy_C", NULL));
  PetscCall(PetscObjectComposeFunction((PetscObject)pc, "PCShellSetSetUp_C", NULL));
  PetscCall(PetscObjectComposeFunction((PetscObject)pc, "PCShellSetApply_C", NULL));
  PetscCall(PetscObjectComposeFunction((PetscObject)pc, "PCShellSetMatApply_C", NULL));
  PetscCall(PetscObjectComposeFunction((PetscObject)pc, "PCShellSetApplySymmetricLeft_C", NULL));
  PetscCall(PetscObjectComposeFunction((PetscObject)pc, "PCShellSetApplySymmetricRight_C", NULL));
  PetscCall(PetscObjectComposeFunction((PetscObject)pc, "PCShellSetApplyBA_C", NULL));
  PetscCall(PetscObjectComposeFunction((PetscObject)pc, "PCShellSetPreSolve_C", NULL));
  PetscCall(PetscObjectComposeFunction((PetscObject)pc, "PCShellSetPostSolve_C", NULL));
  PetscCall(PetscObjectComposeFunction((PetscObject)pc, "PCShellSetView_C", NULL));
  PetscCall(PetscObjectComposeFunction((PetscObject)pc, "PCShellSetApplyTranspose_C", NULL));
  PetscCall(PetscObjectComposeFunction((PetscObject)pc, "PCShellSetName_C", NULL));
  PetscCall(PetscObjectComposeFunction((PetscObject)pc, "PCShellGetName_C", NULL));
  PetscCall(PetscObjectComposeFunction((PetscObject)pc, "PCShellSetApplyRichardson_C", NULL));
  PetscCall(PetscObjectComposeFunction((PetscObject)pc, "PCPreSolveChangeRHS_C", NULL));
  PetscCall(PetscFree(pc->data));
  PetscFunctionReturn(0);
}

static PetscErrorCode PCView_Shell(PC pc, PetscViewer viewer) {
  PC_Shell *shell = (PC_Shell *)pc->data;
  PetscBool iascii;

  PetscFunctionBegin;
  PetscCall(PetscObjectTypeCompare((PetscObject)viewer, PETSCVIEWERASCII, &iascii));
  if (iascii) {
    if (shell->name) PetscCall(PetscViewerASCIIPrintf(viewer, "  %s\n", shell->name));
    else PetscCall(PetscViewerASCIIPrintf(viewer, "  no name\n"));
  }
  if (shell->view) {
    PetscCall(PetscViewerASCIIPushTab(viewer));
    PetscCall((*shell->view)(pc, viewer));
    PetscCall(PetscViewerASCIIPopTab(viewer));
  }
  PetscFunctionReturn(0);
}

static PetscErrorCode PCShellSetDestroy_Shell(PC pc, PetscErrorCode (*destroy)(PC)) {
  PC_Shell *shell = (PC_Shell *)pc->data;

  PetscFunctionBegin;
  shell->destroy = destroy;
  PetscFunctionReturn(0);
}

static PetscErrorCode PCShellSetSetUp_Shell(PC pc, PetscErrorCode (*setup)(PC)) {
  PC_Shell *shell = (PC_Shell *)pc->data;

  PetscFunctionBegin;
  shell->setup = setup;
  if (setup) pc->ops->setup = PCSetUp_Shell;
  else pc->ops->setup = NULL;
  PetscFunctionReturn(0);
}

static PetscErrorCode PCShellSetApply_Shell(PC pc, PetscErrorCode (*apply)(PC, Vec, Vec)) {
  PC_Shell *shell = (PC_Shell *)pc->data;

  PetscFunctionBegin;
  shell->apply = apply;
  PetscFunctionReturn(0);
}

static PetscErrorCode PCShellSetMatApply_Shell(PC pc, PetscErrorCode (*matapply)(PC, Mat, Mat)) {
  PC_Shell *shell = (PC_Shell *)pc->data;

  PetscFunctionBegin;
  shell->matapply = matapply;
  if (matapply) pc->ops->matapply = PCMatApply_Shell;
  else pc->ops->matapply = NULL;
  PetscFunctionReturn(0);
}

static PetscErrorCode PCShellSetApplySymmetricLeft_Shell(PC pc, PetscErrorCode (*apply)(PC, Vec, Vec)) {
  PC_Shell *shell = (PC_Shell *)pc->data;

  PetscFunctionBegin;
  shell->applysymmetricleft = apply;
  PetscFunctionReturn(0);
}

static PetscErrorCode PCShellSetApplySymmetricRight_Shell(PC pc, PetscErrorCode (*apply)(PC, Vec, Vec)) {
  PC_Shell *shell = (PC_Shell *)pc->data;

  PetscFunctionBegin;
  shell->applysymmetricright = apply;
  PetscFunctionReturn(0);
}

static PetscErrorCode PCShellSetApplyBA_Shell(PC pc, PetscErrorCode (*applyBA)(PC, PCSide, Vec, Vec, Vec)) {
  PC_Shell *shell = (PC_Shell *)pc->data;

  PetscFunctionBegin;
  shell->applyBA = applyBA;
  if (applyBA) pc->ops->applyBA = PCApplyBA_Shell;
  else pc->ops->applyBA = NULL;
  PetscFunctionReturn(0);
}

static PetscErrorCode PCShellSetPreSolve_Shell(PC pc, PetscErrorCode (*presolve)(PC, KSP, Vec, Vec)) {
  PC_Shell *shell = (PC_Shell *)pc->data;

  PetscFunctionBegin;
  shell->presolve = presolve;
  if (presolve) {
    pc->ops->presolve = PCPreSolve_Shell;
    PetscCall(PetscObjectComposeFunction((PetscObject)pc, "PCPreSolveChangeRHS_C", PCPreSolveChangeRHS_Shell));
  } else {
    pc->ops->presolve = NULL;
    PetscCall(PetscObjectComposeFunction((PetscObject)pc, "PCPreSolveChangeRHS_C", NULL));
  }
  PetscFunctionReturn(0);
}

static PetscErrorCode PCShellSetPostSolve_Shell(PC pc, PetscErrorCode (*postsolve)(PC, KSP, Vec, Vec)) {
  PC_Shell *shell = (PC_Shell *)pc->data;

  PetscFunctionBegin;
  shell->postsolve = postsolve;
  if (postsolve) pc->ops->postsolve = PCPostSolve_Shell;
  else pc->ops->postsolve = NULL;
  PetscFunctionReturn(0);
}

static PetscErrorCode PCShellSetView_Shell(PC pc, PetscErrorCode (*view)(PC, PetscViewer)) {
  PC_Shell *shell = (PC_Shell *)pc->data;

  PetscFunctionBegin;
  shell->view = view;
  PetscFunctionReturn(0);
}

static PetscErrorCode PCShellSetApplyTranspose_Shell(PC pc, PetscErrorCode (*applytranspose)(PC, Vec, Vec)) {
  PC_Shell *shell = (PC_Shell *)pc->data;

  PetscFunctionBegin;
  shell->applytranspose = applytranspose;
  if (applytranspose) pc->ops->applytranspose = PCApplyTranspose_Shell;
  else pc->ops->applytranspose = NULL;
  PetscFunctionReturn(0);
}

static PetscErrorCode PCShellSetApplyRichardson_Shell(PC pc, PetscErrorCode (*applyrich)(PC, Vec, Vec, Vec, PetscReal, PetscReal, PetscReal, PetscInt, PetscBool, PetscInt *, PCRichardsonConvergedReason *)) {
  PC_Shell *shell = (PC_Shell *)pc->data;

  PetscFunctionBegin;
  shell->applyrich = applyrich;
  if (applyrich) pc->ops->applyrichardson = PCApplyRichardson_Shell;
  else pc->ops->applyrichardson = NULL;
  PetscFunctionReturn(0);
}

static PetscErrorCode PCShellSetName_Shell(PC pc, const char name[]) {
  PC_Shell *shell = (PC_Shell *)pc->data;

  PetscFunctionBegin;
  PetscCall(PetscFree(shell->name));
  PetscCall(PetscStrallocpy(name, &shell->name));
  PetscFunctionReturn(0);
}

static PetscErrorCode PCShellGetName_Shell(PC pc, const char *name[]) {
  PC_Shell *shell = (PC_Shell *)pc->data;

  PetscFunctionBegin;
  *name = shell->name;
  PetscFunctionReturn(0);
}

/*@C
   PCShellSetDestroy - Sets routine to use to destroy the user-provided
   application context.

   Logically Collective on pc

   Input Parameters:
+  pc - the preconditioner context
-  destroy - the application-provided destroy routine

   Calling sequence of destroy:
.vb
   PetscErrorCode destroy (PC)
.ve

.  ptr - the application context

   Note:
    the function MUST return an error code of 0 on success and nonzero on failure.

   Level: intermediate

.seealso: `PCSHELL`, `PCShellSetApply()`, `PCShellSetContext()`
@*/
PetscErrorCode PCShellSetDestroy(PC pc, PetscErrorCode (*destroy)(PC)) {
  PetscFunctionBegin;
  PetscValidHeaderSpecific(pc, PC_CLASSID, 1);
  PetscTryMethod(pc, "PCShellSetDestroy_C", (PC, PetscErrorCode(*)(PC)), (pc, destroy));
  PetscFunctionReturn(0);
}

/*@C
   PCShellSetSetUp - Sets routine to use to "setup" the preconditioner whenever the
   matrix operator is changed.

   Logically Collective on pc

   Input Parameters:
+  pc - the preconditioner context
-  setup - the application-provided setup routine

   Calling sequence of setup:
.vb
   PetscErrorCode setup (PC pc)
.ve

.  pc - the preconditioner, get the application context with PCShellGetContext()

   Note:
    the function MUST return an error code of 0 on success and nonzero on failure.

   Level: intermediate

.seealso: `PCSHELL`, `PCShellSetApplyRichardson()`, `PCShellSetApply()`, `PCShellSetContext()`
@*/
PetscErrorCode PCShellSetSetUp(PC pc, PetscErrorCode (*setup)(PC)) {
  PetscFunctionBegin;
  PetscValidHeaderSpecific(pc, PC_CLASSID, 1);
  PetscTryMethod(pc, "PCShellSetSetUp_C", (PC, PetscErrorCode(*)(PC)), (pc, setup));
  PetscFunctionReturn(0);
}

/*@C
   PCShellSetView - Sets routine to use as viewer of shell preconditioner

   Logically Collective on pc

   Input Parameters:
+  pc - the preconditioner context
-  view - the application-provided view routine

   Calling sequence of view:
.vb
   PetscErrorCode view(PC pc,PetscViewer v)
.ve

+  pc - the preconditioner, get the application context with PCShellGetContext()
-  v   - viewer

   Note:
    the function MUST return an error code of 0 on success and nonzero on failure.

   Level: advanced

.seealso: `PCSHELL`, `PCShellSetApplyRichardson()`, `PCShellSetSetUp()`, `PCShellSetApplyTranspose()`
@*/
PetscErrorCode PCShellSetView(PC pc, PetscErrorCode (*view)(PC, PetscViewer)) {
  PetscFunctionBegin;
  PetscValidHeaderSpecific(pc, PC_CLASSID, 1);
  PetscTryMethod(pc, "PCShellSetView_C", (PC, PetscErrorCode(*)(PC, PetscViewer)), (pc, view));
  PetscFunctionReturn(0);
}

/*@C
   PCShellSetApply - Sets routine to use as preconditioner.

   Logically Collective on pc

   Input Parameters:
+  pc - the preconditioner context
-  apply - the application-provided preconditioning routine

   Calling sequence of apply:
.vb
   PetscErrorCode apply (PC pc,Vec xin,Vec xout)
.ve

+  pc - the preconditioner, get the application context with PCShellGetContext()
.  xin - input vector
-  xout - output vector

   Note:
    the function MUST return an error code of 0 on success and nonzero on failure.

   Level: intermediate

.seealso: `PCSHELL`, `PCShellSetApplyRichardson()`, `PCShellSetSetUp()`, `PCShellSetApplyTranspose()`, `PCShellSetContext()`, `PCShellSetApplyBA()`, `PCShellSetApplySymmetricRight()`, `PCShellSetApplySymmetricLeft()`
@*/
PetscErrorCode PCShellSetApply(PC pc, PetscErrorCode (*apply)(PC, Vec, Vec)) {
  PetscFunctionBegin;
  PetscValidHeaderSpecific(pc, PC_CLASSID, 1);
  PetscTryMethod(pc, "PCShellSetApply_C", (PC, PetscErrorCode(*)(PC, Vec, Vec)), (pc, apply));
  PetscFunctionReturn(0);
}

/*@C
   PCShellSetMatApply - Sets routine to use as preconditioner on a block of vectors.

   Logically Collective on pc

   Input Parameters:
+  pc - the preconditioner context
-  apply - the application-provided preconditioning routine

   Calling sequence of apply:
.vb
   PetscErrorCode apply (PC pc,Mat Xin,Mat Xout)
.ve

+  pc - the preconditioner, get the application context with PCShellGetContext()
.  Xin - input block of vectors
-  Xout - output block of vectors

   Note:
   The function MUST return an error code of 0 on success and nonzero on failure.

   Level: advanced

.seealso: `PCSHELL`, `PCShellSetApply()`
@*/
PetscErrorCode PCShellSetMatApply(PC pc, PetscErrorCode (*matapply)(PC, Mat, Mat)) {
  PetscFunctionBegin;
  PetscValidHeaderSpecific(pc, PC_CLASSID, 1);
  PetscTryMethod(pc, "PCShellSetMatApply_C", (PC, PetscErrorCode(*)(PC, Mat, Mat)), (pc, matapply));
  PetscFunctionReturn(0);
}

/*@C
   PCShellSetApplySymmetricLeft - Sets routine to use as left preconditioner (when the `PC_SYMMETRIC` is used).

   Logically Collective on pc

   Input Parameters:
+  pc - the preconditioner context
-  apply - the application-provided left preconditioning routine

   Calling sequence of apply:
.vb
   PetscErrorCode apply (PC pc,Vec xin,Vec xout)
.ve

+  pc - the preconditioner, get the application context with `PCShellGetContext()`
.  xin - input vector
-  xout - output vector

   Note:
  The function MUST return an error code of 0 on success and nonzero on failure.

   Level: advanced

.seealso: `PCSHELL`, `PCShellSetApply()`, `PCShellSetApplySymmetricLeft()`, `PCShellSetSetUp()`, `PCShellSetApplyTranspose()`, `PCShellSetContext()`
@*/
PetscErrorCode PCShellSetApplySymmetricLeft(PC pc, PetscErrorCode (*apply)(PC, Vec, Vec)) {
  PetscFunctionBegin;
  PetscValidHeaderSpecific(pc, PC_CLASSID, 1);
  PetscTryMethod(pc, "PCShellSetApplySymmetricLeft_C", (PC, PetscErrorCode(*)(PC, Vec, Vec)), (pc, apply));
  PetscFunctionReturn(0);
}

/*@C
   PCShellSetApplySymmetricRight - Sets routine to use as right preconditioner (when the `PC_SYMMETRIC` is used).

   Logically Collective on pc

   Input Parameters:
+  pc - the preconditioner context
-  apply - the application-provided right preconditioning routine

   Calling sequence of apply:
.vb
   PetscErrorCode apply (PC pc,Vec xin,Vec xout)
.ve

+  pc - the preconditioner, get the application context with PCShellGetContext()
.  xin - input vector
-  xout - output vector

   Note:
   The function MUST return an error code of 0 on success and nonzero on failure.

   Level: advanced

.seealso: `PCSHELL`, `PCShellSetApply()`, `PCShellSetApplySymmetricLeft()`, `PCShellSetSetUp()`, `PCShellSetApplyTranspose()`, `PCShellSetContext()`
@*/
PetscErrorCode PCShellSetApplySymmetricRight(PC pc, PetscErrorCode (*apply)(PC, Vec, Vec)) {
  PetscFunctionBegin;
  PetscValidHeaderSpecific(pc, PC_CLASSID, 1);
  PetscTryMethod(pc, "PCShellSetApplySymmetricRight_C", (PC, PetscErrorCode(*)(PC, Vec, Vec)), (pc, apply));
  PetscFunctionReturn(0);
}

/*@C
   PCShellSetApplyBA - Sets routine to use as preconditioner times operator.

   Logically Collective on pc

   Input Parameters:
+  pc - the preconditioner context
-  applyBA - the application-provided BA routine

   Calling sequence of applyBA:
.vb
   PetscErrorCode applyBA (PC pc,Vec xin,Vec xout)
.ve

+  pc - the preconditioner, get the application context with PCShellGetContext()
.  xin - input vector
-  xout - output vector

   Note:
   The function MUST return an error code of 0 on success and nonzero on failure.

   Level: intermediate

.seealso: `PCSHELL`, `PCShellSetApplyRichardson()`, `PCShellSetSetUp()`, `PCShellSetApplyTranspose()`, `PCShellSetContext()`, `PCShellSetApply()`
@*/
PetscErrorCode PCShellSetApplyBA(PC pc, PetscErrorCode (*applyBA)(PC, PCSide, Vec, Vec, Vec)) {
  PetscFunctionBegin;
  PetscValidHeaderSpecific(pc, PC_CLASSID, 1);
  PetscTryMethod(pc, "PCShellSetApplyBA_C", (PC, PetscErrorCode(*)(PC, PCSide, Vec, Vec, Vec)), (pc, applyBA));
  PetscFunctionReturn(0);
}

/*@C
   PCShellSetApplyTranspose - Sets routine to use as preconditioner transpose.

   Logically Collective on pc

   Input Parameters:
+  pc - the preconditioner context
-  apply - the application-provided preconditioning transpose routine

   Calling sequence of apply:
.vb
   PetscErrorCode applytranspose (PC pc,Vec xin,Vec xout)
.ve

+  pc - the preconditioner, get the application context with PCShellGetContext()
.  xin - input vector
-  xout - output vector

   Note:
    the function MUST return an error code of 0 on success and nonzero on failure.

   Level: intermediate

   Note:
   Uses the same context variable as `PCShellSetApply()`.

.seealso: `PCSHELL`, `PCShellSetApplyRichardson()`, `PCShellSetSetUp()`, `PCShellSetApply()`, `PCSetContext()`, `PCShellSetApplyBA()`
@*/
PetscErrorCode PCShellSetApplyTranspose(PC pc, PetscErrorCode (*applytranspose)(PC, Vec, Vec)) {
  PetscFunctionBegin;
  PetscValidHeaderSpecific(pc, PC_CLASSID, 1);
  PetscTryMethod(pc, "PCShellSetApplyTranspose_C", (PC, PetscErrorCode(*)(PC, Vec, Vec)), (pc, applytranspose));
  PetscFunctionReturn(0);
}

/*@C
   PCShellSetPreSolve - Sets routine to apply to the operators/vectors before a `KSPSolve()` is
      applied. This usually does something like scale the linear system in some application
      specific way.

   Logically Collective on pc

   Input Parameters:
+  pc - the preconditioner context
-  presolve - the application-provided presolve routine

   Calling sequence of presolve:
.vb
   PetscErrorCode presolve (PC,KSP ksp,Vec b,Vec x)
.ve

+  pc - the preconditioner, get the application context with PCShellGetContext()
.  xin - input vector
-  xout - output vector

   Note:
   The function MUST return an error code of 0 on success and nonzero on failure.

   Level: advanced

.seealso: `PCSHELL`, `PCShellSetApplyRichardson()`, `PCShellSetSetUp()`, `PCShellSetApplyTranspose()`, `PCShellSetPostSolve()`, `PCShellSetContext()`
@*/
PetscErrorCode PCShellSetPreSolve(PC pc, PetscErrorCode (*presolve)(PC, KSP, Vec, Vec)) {
  PetscFunctionBegin;
  PetscValidHeaderSpecific(pc, PC_CLASSID, 1);
  PetscTryMethod(pc, "PCShellSetPreSolve_C", (PC, PetscErrorCode(*)(PC, KSP, Vec, Vec)), (pc, presolve));
  PetscFunctionReturn(0);
}

/*@C
   PCShellSetPostSolve - Sets routine to apply to the operators/vectors before a `KSPSolve()` is
      applied. This usually does something like scale the linear system in some application
      specific way.

   Logically Collective on pc

   Input Parameters:
+  pc - the preconditioner context
-  postsolve - the application-provided presolve routine

   Calling sequence of postsolve:
.vb
   PetscErrorCode postsolve(PC,KSP ksp,Vec b,Vec x)
.ve

+  pc - the preconditioner, get the application context with `PCShellGetContext()`
.  xin - input vector
-  xout - output vector

   Note:
    the function MUST return an error code of 0 on success and nonzero on failure.

   Level: advanced

.seealso: `PCSHELL`, `PCShellSetApplyRichardson()`, `PCShellSetSetUp()`, `PCShellSetApplyTranspose()`, `PCShellSetPreSolve()`, `PCShellSetContext()`
@*/
PetscErrorCode PCShellSetPostSolve(PC pc, PetscErrorCode (*postsolve)(PC, KSP, Vec, Vec)) {
  PetscFunctionBegin;
  PetscValidHeaderSpecific(pc, PC_CLASSID, 1);
  PetscTryMethod(pc, "PCShellSetPostSolve_C", (PC, PetscErrorCode(*)(PC, KSP, Vec, Vec)), (pc, postsolve));
  PetscFunctionReturn(0);
}

/*@C
   PCShellSetName - Sets an optional name to associate with a `PCSHELL`
   preconditioner.

   Not Collective

   Input Parameters:
+  pc - the preconditioner context
-  name - character string describing shell preconditioner

   Level: intermediate

.seealso: `PCSHELL`, `PCShellGetName()`
@*/
PetscErrorCode PCShellSetName(PC pc, const char name[]) {
  PetscFunctionBegin;
  PetscValidHeaderSpecific(pc, PC_CLASSID, 1);
  PetscTryMethod(pc, "PCShellSetName_C", (PC, const char[]), (pc, name));
  PetscFunctionReturn(0);
}

/*@C
   PCShellGetName - Gets an optional name that the user has set for a `PCSHELL`
   preconditioner.

   Not Collective

   Input Parameter:
.  pc - the preconditioner context

   Output Parameter:
.  name - character string describing shell preconditioner (you should not free this)

   Level: intermediate

.seealso: `PCSHELL`, `PCShellSetName()`
@*/
PetscErrorCode PCShellGetName(PC pc, const char *name[]) {
  PetscFunctionBegin;
  PetscValidHeaderSpecific(pc, PC_CLASSID, 1);
  PetscValidPointer(name, 2);
  PetscUseMethod(pc, "PCShellGetName_C", (PC, const char *[]), (pc, name));
  PetscFunctionReturn(0);
}

/*@C
   PCShellSetApplyRichardson - Sets routine to use as preconditioner
   in Richardson iteration.

   Logically Collective on pc

   Input Parameters:
+  pc - the preconditioner context
-  apply - the application-provided preconditioning routine

   Calling sequence of apply:
.vb
   PetscErrorCode apply (PC pc,Vec b,Vec x,Vec r,PetscReal rtol,PetscReal abstol,PetscReal dtol,PetscInt maxits)
.ve

+  pc - the preconditioner, get the application context with PCShellGetContext()
.  b - right-hand-side
.  x - current iterate
.  r - work space
.  rtol - relative tolerance of residual norm to stop at
.  abstol - absolute tolerance of residual norm to stop at
.  dtol - if residual norm increases by this factor than return
-  maxits - number of iterations to run

   Note:
    the function MUST return an error code of 0 on success and nonzero on failure.

   Level: advanced

.seealso: `PCShellSetApply()`, `PCShellSetContext()`
@*/
PetscErrorCode PCShellSetApplyRichardson(PC pc, PetscErrorCode (*apply)(PC, Vec, Vec, Vec, PetscReal, PetscReal, PetscReal, PetscInt, PetscBool, PetscInt *, PCRichardsonConvergedReason *)) {
  PetscFunctionBegin;
  PetscValidHeaderSpecific(pc, PC_CLASSID, 1);
  PetscTryMethod(pc, "PCShellSetApplyRichardson_C", (PC, PetscErrorCode(*)(PC, Vec, Vec, Vec, PetscReal, PetscReal, PetscReal, PetscInt, PetscBool, PetscInt *, PCRichardsonConvergedReason *)), (pc, apply));
  PetscFunctionReturn(0);
}

/*MC
   PCSHELL - Creates a new preconditioner class for use with a users
              own private data storage format and preconditioner application code

   Level: advanced

  Usage:
.vb
       extern PetscErrorCode apply(PC,Vec,Vec);
       extern PetscErrorCode applyba(PC,PCSide,Vec,Vec,Vec);
       extern PetscErrorCode applytranspose(PC,Vec,Vec);
       extern PetscErrorCode setup(PC);
       extern PetscErrorCode destroy(PC);

       PCCreate(comm,&pc);
       PCSetType(pc,PCSHELL);
       PCShellSetContext(pc,ctx)
       PCShellSetApply(pc,apply);
       PCShellSetApplyBA(pc,applyba);               (optional)
       PCShellSetApplyTranspose(pc,applytranspose); (optional)
       PCShellSetSetUp(pc,setup);                   (optional)
       PCShellSetDestroy(pc,destroy);               (optional)
.ve

.seealso: `PCCreate()`, `PCSetType()`, `PCType`, `PC`,
          `MATSHELL`, `PCShellSetSetUp()`, `PCShellSetApply()`, `PCShellSetView()`, `PCShellSetDestroy()`, `PCShellSetPostSolve()`,
          `PCShellSetApplyTranspose()`, `PCShellSetName()`, `PCShellSetApplyRichardson()`, `PCShellSetPreSolve()`, `PCShellSetView()`,
          `PCShellGetName()`, `PCShellSetContext()`, `PCShellGetContext()`, `PCShellSetApplyBA()`, `MATSHELL`, `PCShellSetMatApply()`,
M*/

PETSC_EXTERN PetscErrorCode PCCreate_Shell(PC pc) {
  PC_Shell *shell;

  PetscFunctionBegin;
  PetscCall(PetscNew(&shell));
  pc->data = (void *)shell;

  pc->ops->destroy             = PCDestroy_Shell;
  pc->ops->view                = PCView_Shell;
  pc->ops->apply               = PCApply_Shell;
  pc->ops->applysymmetricleft  = PCApplySymmetricLeft_Shell;
  pc->ops->applysymmetricright = PCApplySymmetricRight_Shell;
  pc->ops->matapply            = NULL;
  pc->ops->applytranspose      = NULL;
  pc->ops->applyrichardson     = NULL;
  pc->ops->setup               = NULL;
  pc->ops->presolve            = NULL;
  pc->ops->postsolve           = NULL;

  shell->apply               = NULL;
  shell->applytranspose      = NULL;
  shell->name                = NULL;
  shell->applyrich           = NULL;
  shell->presolve            = NULL;
  shell->postsolve           = NULL;
  shell->ctx                 = NULL;
  shell->setup               = NULL;
  shell->view                = NULL;
  shell->destroy             = NULL;
  shell->applysymmetricleft  = NULL;
  shell->applysymmetricright = NULL;

  PetscCall(PetscObjectComposeFunction((PetscObject)pc, "PCShellSetDestroy_C", PCShellSetDestroy_Shell));
  PetscCall(PetscObjectComposeFunction((PetscObject)pc, "PCShellSetSetUp_C", PCShellSetSetUp_Shell));
  PetscCall(PetscObjectComposeFunction((PetscObject)pc, "PCShellSetApply_C", PCShellSetApply_Shell));
  PetscCall(PetscObjectComposeFunction((PetscObject)pc, "PCShellSetMatApply_C", PCShellSetMatApply_Shell));
  PetscCall(PetscObjectComposeFunction((PetscObject)pc, "PCShellSetApplySymmetricLeft_C", PCShellSetApplySymmetricLeft_Shell));
  PetscCall(PetscObjectComposeFunction((PetscObject)pc, "PCShellSetApplySymmetricRight_C", PCShellSetApplySymmetricRight_Shell));
  PetscCall(PetscObjectComposeFunction((PetscObject)pc, "PCShellSetApplyBA_C", PCShellSetApplyBA_Shell));
  PetscCall(PetscObjectComposeFunction((PetscObject)pc, "PCShellSetPreSolve_C", PCShellSetPreSolve_Shell));
  PetscCall(PetscObjectComposeFunction((PetscObject)pc, "PCShellSetPostSolve_C", PCShellSetPostSolve_Shell));
  PetscCall(PetscObjectComposeFunction((PetscObject)pc, "PCShellSetView_C", PCShellSetView_Shell));
  PetscCall(PetscObjectComposeFunction((PetscObject)pc, "PCShellSetApplyTranspose_C", PCShellSetApplyTranspose_Shell));
  PetscCall(PetscObjectComposeFunction((PetscObject)pc, "PCShellSetName_C", PCShellSetName_Shell));
  PetscCall(PetscObjectComposeFunction((PetscObject)pc, "PCShellGetName_C", PCShellGetName_Shell));
  PetscCall(PetscObjectComposeFunction((PetscObject)pc, "PCShellSetApplyRichardson_C", PCShellSetApplyRichardson_Shell));
  PetscFunctionReturn(0);
}