[petsc-dev] multiple dispatch code currently in PETSc

[Barry Smith]

  Do we really want mallocs for EVERY single multiple-dispatch function call in PETSc? I suggest not having MatQueryOp() but calling directly PetscOpFListFind() (with the MatOpFList argument) and changing PetscOpFListAdd/Find() to use variable args directly.

   Finally do we really want string comparisons at all here? Or do we want XXXRegister() (for example, MatRegister()) to compute an integer type id to go with each char *type_name and do the search off the integer type id instead of strings? Thus making PetscOpFListFind() super light weight?

   Barry


PetscErrorCode  MatQueryOp(MPI_Comm comm, PetscVoidFunction* function, const char op[], PetscInt numArgs, ...) 
{
  PetscErrorCode ierr;
  va_list        ap;
  PetscInt       i;
  const char     *argType;
  char           **argTypes = PETSC_NULL;

  PetscFunctionBegin;
  va_start(ap,numArgs);
  if (numArgs) {
    ierr = PetscMalloc(sizeof(char*)*numArgs, &argTypes);CHKERRQ(ierr);
  }
  for (i = 0; i < numArgs; ++i) {
    argType = va_arg(ap,const char*);
    ierr = PetscStrallocpy(argType, argTypes+i);CHKERRQ(ierr);
  }
  va_end(ap);
  ierr = PetscOpFListFind(comm, MatOpList, function, op, numArgs, argTypes);CHKERRQ(ierr);
  for (i = 0; i < numArgs; ++i) {
    ierr = PetscFree(argTypes[i]);CHKERRQ(ierr);
  }
  ierr = PetscFree(argTypes);CHKERRQ(ierr);
  PetscFunctionReturn(0);
}