Date: 2026-06-01T23:13:38+00:00

Actual source code: isltog.c

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

      3: PetscErrorCode MatCreateFromISLocalToGlobalMapping(ISLocalToGlobalMapping lgmap, Mat A, PetscBool cols, PetscBool trans, MatType ptype, Mat *P)
      4: {
      5:   PetscBool       matfree = PETSC_FALSE;
      6:   const PetscInt *idxs;
      7:   PetscInt        msize, *pidxs, c = 0;

      9:   PetscFunctionBegin;
     15:   PetscAssertPointer(P, 6);

     17:   if (!ptype) PetscCall(MatGetType(A, &ptype));
     18:   PetscCall(PetscStrcmpAny(ptype, &matfree, MATSHELL, MATSCATTER, ""));
     19:   PetscCall(ISLocalToGlobalMappingGetIndices(lgmap, &idxs));
     20:   PetscCall(ISLocalToGlobalMappingGetSize(lgmap, &msize));
     21:   PetscCall(PetscMalloc1(msize, &pidxs));
     22:   for (PetscInt i = 0; i < msize; i++)
     23:     if (idxs[i] >= 0) pidxs[c++] = idxs[i];
     24:   PetscCall(ISLocalToGlobalMappingRestoreIndices(lgmap, &idxs));
     25:   msize = c;
     26:   if (matfree) {
     27:     Vec        v, lv;
     28:     VecType    vtype;
     29:     IS         is;
     30:     VecScatter sct;
     31:     PetscBool  matshell;

     33:     if (cols) PetscCall(MatCreateVecs(A, &v, NULL));
     34:     else PetscCall(MatCreateVecs(A, NULL, &v));
     35:     PetscCall(VecGetType(v, &vtype));
     36:     PetscCall(VecCreate(PETSC_COMM_SELF, &lv));
     37:     PetscCall(VecSetSizes(lv, msize, PETSC_DECIDE));
     38:     PetscCall(VecSetType(lv, vtype));
     39:     PetscCall(ISCreateGeneral(PetscObjectComm((PetscObject)A), msize, pidxs, PETSC_USE_POINTER, &is));
     40:     if (trans) PetscCall(VecScatterCreate(lv, NULL, v, is, &sct));
     41:     else PetscCall(VecScatterCreate(v, is, lv, NULL, &sct));
     42:     PetscCall(MatCreateScatter(PetscObjectComm((PetscObject)A), sct, P));
     43:     PetscCall(PetscStrcmp(ptype, MATSHELL, &matshell));
     44:     if (matshell) {
     45:       Mat tP;
     46:       PetscCall(MatConvert(*P, ptype, MAT_INITIAL_MATRIX, &tP));
     47:       PetscCall(MatDestroy(P));
     48:       *P = tP;
     49:     }
     50:     PetscCall(ISDestroy(&is));
     51:     PetscCall(VecScatterDestroy(&sct));
     52:     PetscCall(VecDestroy(&lv));
     53:     PetscCall(VecDestroy(&v));
     54:   } else {
     55:     PetscInt lar, lac, rst;

     57:     PetscCall(MatGetLocalSize(A, &lar, &lac));
     58:     PetscCall(MatCreate(PetscObjectComm((PetscObject)A), P));
     59:     PetscCall(MatSetType(*P, ptype));
     60:     PetscCall(MatSetSizes(*P, msize, cols ? lac : lar, PETSC_DECIDE, PETSC_DECIDE));
     61:     PetscCall(MatSeqAIJSetPreallocation(*P, 1, NULL));
     62:     PetscCall(MatMPIAIJSetPreallocation(*P, 1, NULL, 1, NULL));
     63: #if defined(PETSC_HAVE_HYPRE)
     64:     PetscCall(MatHYPRESetPreallocation(*P, 1, NULL, 1, NULL));
     65: #endif
     66:     PetscCall(MatGetOwnershipRange(*P, &rst, NULL));
     67:     for (PetscInt i = 0; i < msize; i++) PetscCall(MatSetValue(*P, i + rst, pidxs[i], 1.0, INSERT_VALUES));
     68:     PetscCall(MatAssemblyBegin(*P, MAT_FINAL_ASSEMBLY));
     69:     PetscCall(MatAssemblyEnd(*P, MAT_FINAL_ASSEMBLY));
     70:     if (trans) {
     71:       Mat tP;
     72:       PetscCall(MatTranspose(*P, MAT_INITIAL_MATRIX, &tP));
     73:       PetscCall(MatDestroy(P));
     74:       *P = tP;
     75:     }
     76:   }
     77:   PetscCall(PetscFree(pidxs));
     78:   PetscFunctionReturn(PETSC_SUCCESS);
     79: }