Date: 2026-03-01T05:25:26+00:00

Actual source code: ex1.c

      1: static char help[] = "Basic vector routines.\n\n";

      3: /*
      4:   Include "petscvec.h" so that we can use vectors.  Note that this file
      5:   automatically includes:
      6:      petscsys.h       - base PETSc routines   petscis.h     - index sets
      7:      petscviewer.h - viewers
      8: */

     10: #include <petscvec.h>

     12: int main(int argc, char **argv)
     13: {
     14:   Vec         x, y, w; /* vectors */
     15:   Vec        *z;       /* array of vectors */
     16:   PetscReal   norm, v, v1, v2, maxval;
     17:   PetscInt    n   = 20, maxind;
     18:   PetscScalar one = 1.0, two = 2.0, three = 3.0, dots[3], dot;

     20:   PetscFunctionBeginUser;
     21:   PetscCall(PetscInitialize(&argc, &argv, NULL, help));
     22:   PetscCall(PetscOptionsGetInt(NULL, NULL, "-n", &n, NULL));

     24:   /*
     25:      Create a vector, specifying only its global dimension.
     26:      When using VecCreate(), VecSetSizes() and VecSetFromOptions(), the vector format
     27:      (currently parallel, shared, or sequential) is determined at runtime.  Also, the
     28:      parallel partitioning of the vector is determined by PETSc at runtime.
     29:   */
     30:   PetscCall(VecCreate(PETSC_COMM_WORLD, &x));
     31:   PetscCall(VecSetSizes(x, PETSC_DECIDE, n));
     32:   PetscCall(VecSetFromOptions(x));

     34:   /*
     35:      Duplicate some work vectors (of the same format and
     36:      partitioning as the initial vector).
     37:   */
     38:   PetscCall(VecDuplicate(x, &y));
     39:   PetscCall(VecDuplicate(x, &w));

     41:   /*
     42:      Duplicate more work vectors (of the same format and
     43:      partitioning as the initial vector).  Here we duplicate
     44:      an array of vectors, which is often more convenient than
     45:      duplicating individual ones.
     46:   */
     47:   PetscCall(VecDuplicateVecs(x, 3, &z));
     48:   /*
     49:      Set the vectors to entries to a constant value.
     50:   */
     51:   PetscCall(VecSet(x, one));
     52:   PetscCall(VecSet(y, two));
     53:   PetscCall(VecSet(z[0], one));
     54:   PetscCall(VecSet(z[1], two));
     55:   PetscCall(VecSet(z[2], three));
     56:   /*
     57:      Demonstrate various basic vector routines.
     58:   */
     59:   PetscCall(VecDot(x, y, &dot));
     60:   PetscCall(VecMDot(x, 3, z, dots));

     62:   /*
     63:      Note: If using a complex numbers version of PETSc, then
     64:      PETSC_USE_COMPLEX is defined in the makefiles; otherwise,
     65:      (when using real numbers) it is undefined.
     66:   */

     68:   PetscCall(PetscPrintf(PETSC_COMM_WORLD, "Vector length %" PetscInt_FMT "\n", n));
     69:   PetscCall(VecMax(x, &maxind, &maxval));
     70:   PetscCall(PetscPrintf(PETSC_COMM_WORLD, "VecMax %g, VecInd %" PetscInt_FMT "\n", (double)maxval, maxind));

     72:   PetscCall(VecMin(x, &maxind, &maxval));
     73:   PetscCall(PetscPrintf(PETSC_COMM_WORLD, "VecMin %g, VecInd %" PetscInt_FMT "\n", (double)maxval, maxind));
     74:   PetscCall(PetscPrintf(PETSC_COMM_WORLD, "All other values should be near zero\n"));

     76:   PetscCall(VecScale(x, two));
     77:   PetscCall(VecNorm(x, NORM_2, &norm));
     78:   v = norm - 2.0 * PetscSqrtReal((PetscReal)n);
     79:   if (v > -PETSC_SMALL && v < PETSC_SMALL) v = 0.0;
     80:   PetscCall(PetscPrintf(PETSC_COMM_WORLD, "VecScale %g\n", (double)v));

     82:   PetscCall(VecCopy(x, w));
     83:   PetscCall(VecNorm(w, NORM_2, &norm));
     84:   v = norm - 2.0 * PetscSqrtReal((PetscReal)n);
     85:   if (v > -PETSC_SMALL && v < PETSC_SMALL) v = 0.0;
     86:   PetscCall(PetscPrintf(PETSC_COMM_WORLD, "VecCopy  %g\n", (double)v));

     88:   PetscCall(VecAXPY(y, three, x));
     89:   PetscCall(VecNorm(y, NORM_2, &norm));
     90:   v = norm - 8.0 * PetscSqrtReal((PetscReal)n);
     91:   if (v > -PETSC_SMALL && v < PETSC_SMALL) v = 0.0;
     92:   PetscCall(PetscPrintf(PETSC_COMM_WORLD, "VecAXPY %g\n", (double)v));

     94:   PetscCall(VecAYPX(y, two, x));
     95:   PetscCall(VecNorm(y, NORM_2, &norm));
     96:   v = norm - 18.0 * PetscSqrtReal((PetscReal)n);
     97:   if (v > -PETSC_SMALL && v < PETSC_SMALL) v = 0.0;
     98:   PetscCall(PetscPrintf(PETSC_COMM_WORLD, "VecAYPX %g\n", (double)v));

    100:   PetscCall(VecSwap(x, y));
    101:   PetscCall(VecNorm(y, NORM_2, &norm));
    102:   v = norm - 2.0 * PetscSqrtReal((PetscReal)n);
    103:   if (v > -PETSC_SMALL && v < PETSC_SMALL) v = 0.0;
    104:   PetscCall(PetscPrintf(PETSC_COMM_WORLD, "VecSwap  %g\n", (double)v));
    105:   PetscCall(VecNorm(x, NORM_2, &norm));
    106:   v = norm - 18.0 * PetscSqrtReal((PetscReal)n);
    107:   if (v > -PETSC_SMALL && v < PETSC_SMALL) v = 0.0;
    108:   PetscCall(PetscPrintf(PETSC_COMM_WORLD, "VecSwap  %g\n", (double)v));

    110:   PetscCall(VecWAXPY(w, two, x, y));
    111:   PetscCall(VecNorm(w, NORM_2, &norm));
    112:   v = norm - 38.0 * PetscSqrtReal((PetscReal)n);
    113:   if (v > -PETSC_SMALL && v < PETSC_SMALL) v = 0.0;
    114:   PetscCall(PetscPrintf(PETSC_COMM_WORLD, "VecWAXPY %g\n", (double)v));

    116:   PetscCall(VecPointwiseMult(w, y, x));
    117:   PetscCall(VecNorm(w, NORM_2, &norm));
    118:   v = norm - 36.0 * PetscSqrtReal((PetscReal)n);
    119:   if (v > -PETSC_SMALL && v < PETSC_SMALL) v = 0.0;
    120:   PetscCall(PetscPrintf(PETSC_COMM_WORLD, "VecPointwiseMult %g\n", (double)v));

    122:   PetscCall(VecPointwiseDivide(w, x, y));
    123:   PetscCall(VecNorm(w, NORM_2, &norm));
    124:   v = norm - 9.0 * PetscSqrtReal((PetscReal)n);
    125:   if (v > -PETSC_SMALL && v < PETSC_SMALL) v = 0.0;
    126:   PetscCall(PetscPrintf(PETSC_COMM_WORLD, "VecPointwiseDivide %g\n", (double)v));

    128:   PetscCall(VecSetValue(y, 0, 0.0, INSERT_VALUES));
    129:   PetscCall(VecAssemblyBegin(y));
    130:   PetscCall(VecAssemblyEnd(y));
    131:   PetscCall(VecPointwiseDivide(w, x, y));
    132:   PetscCall(VecNorm(w, NORM_2, &norm));
    133:   v = norm - 9.0 * PetscSqrtReal((PetscReal)n);
    134:   if (v > -PETSC_SMALL && v < PETSC_SMALL) v = 0.0;
    135:   PetscCall(PetscPrintf(PETSC_COMM_WORLD, "VecPointwiseDivide %g\n", (double)v));

    137:   dots[0] = one;
    138:   dots[1] = three;
    139:   dots[2] = two;

    141:   PetscCall(VecSet(x, one));
    142:   PetscCall(VecMAXPY(x, 3, dots, z));
    143:   PetscCall(VecNorm(z[0], NORM_2, &norm));
    144:   v = norm - PetscSqrtReal((PetscReal)n);
    145:   if (v > -PETSC_SMALL && v < PETSC_SMALL) v = 0.0;
    146:   PetscCall(VecNorm(z[1], NORM_2, &norm));
    147:   v1 = norm - 2.0 * PetscSqrtReal((PetscReal)n);
    148:   if (v1 > -PETSC_SMALL && v1 < PETSC_SMALL) v1 = 0.0;
    149:   PetscCall(VecNorm(z[2], NORM_2, &norm));
    150:   v2 = norm - 3.0 * PetscSqrtReal((PetscReal)n);
    151:   if (v2 > -PETSC_SMALL && v2 < PETSC_SMALL) v2 = 0.0;
    152:   PetscCall(PetscPrintf(PETSC_COMM_WORLD, "VecMAXPY %g %g %g \n", (double)v, (double)v1, (double)v2));

    154:   /*
    155:      Free work space.  All PETSc objects should be destroyed when they
    156:      are no longer needed.
    157:   */
    158:   PetscCall(VecDestroy(&x));
    159:   PetscCall(VecDestroy(&y));
    160:   PetscCall(VecDestroy(&w));
    161:   PetscCall(VecDestroyVecs(3, &z));
    162:   PetscCall(PetscFinalize());
    163:   return 0;
    164: }

    166: /*TEST

    168:   testset:
    169:     output_file: output/ex1_1.out
    170:     # This is a test where the exact numbers are critical
    171:     diff_args: -j

    173:     test:

    175:     test:
    176:         suffix: cuda
    177:         args: -vec_type cuda
    178:         requires: cuda

    180:     test:
    181:         suffix: kokkos
    182:         args: -vec_type kokkos
    183:         requires: kokkos_kernels

    185:     test:
    186:         suffix: hip
    187:         args: -vec_type hip
    188:         requires: hip

    190:     test:
    191:         suffix: 2
    192:         nsize: 2

    194:     test:
    195:         suffix: 2_cuda
    196:         nsize: 2
    197:         args: -vec_type cuda
    198:         requires: cuda

    200:     test:
    201:         suffix: 2_kokkos
    202:         nsize: 2
    203:         args: -vec_type kokkos
    204:         requires: kokkos_kernels

    206:     test:
    207:         suffix: 2_hip
    208:         nsize: 2
    209:         args: -vec_type hip
    210:         requires: hip

    212: TEST*/