Date: 2021-03-03T22:27:32+00:00

Actual source code: ex10.c
petsc-3.14.5 2021-03-03
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      2: static char help[] = "Solve a small system and a large system through preloading\n\
      3:   Input arguments are:\n\
      4:    -f0 <small_sys_binary> -f1 <large_sys_binary> \n\n";

      6: /*T
      7:    Concepts: KSP^basic parallel example
      8:    Concepts: Mat^loading a binary matrix and vector;
      9:    Concepts: PetscLog^preloading executable
     10:    Processors: n
     11: T*/

     13: /*
     14:   Include "petscksp.h" so that we can use KSP solvers.  Note that this file
     15:   automatically includes:
     16:      petscsys.h       - base PETSc routines   petscvec.h - vectors
     17:      petscmat.h - matrices
     18:      petscis.h     - index sets            petscksp.h - Krylov subspace methods
     19:      petscviewer.h - viewers               petscpc.h  - preconditioners
     20: */
     21: #include <petscksp.h>

     23: typedef enum {
     24:   RHS_FILE,
     25:   RHS_ONE,
     26:   RHS_RANDOM
     27: } RHSType;
     28: const char *const RHSTypes[] = {"FILE", "ONE", "RANDOM", "RHSType", "RHS_", NULL};

     30: /* ATTENTION: this is the example used in the Profiling chaper of the PETSc manual,
     31:    where we referenced its profiling stages, preloading and output etc.
     32:    When you modify it, please make sure it is still consistent with the manual.
     33:  */
     34: int main(int argc,char **args)
     35: {
     36:   PetscErrorCode    ierr;
     37:   Vec               x,b,b2;
     38:   Mat               A;           /* linear system matrix */
     39:   KSP               ksp;         /* Krylov subspace method context */
     40:   PetscReal         norm;        /* norm of solution error */
     41:   char              file[2][PETSC_MAX_PATH_LEN];
     42:   PetscViewer       viewer;      /* viewer */
     43:   PetscBool         flg,preload=PETSC_FALSE,same,trans=PETSC_FALSE;
     44:   RHSType           rhstype = RHS_FILE;
     45:   PetscInt          its,j,len,start,idx,n1,n2;
     46:   const PetscScalar *val;

     48:   PetscInitialize(&argc,&args,(char*)0,help);if (ierr) return ierr;

     50:   /*
     51:      Determine files from which we read the two linear systems
     52:      (matrix and right-hand-side vector).
     53:   */
     54:   PetscOptionsGetBool(NULL,NULL,"-trans",&trans,&flg);
     55:   PetscOptionsGetString(NULL,NULL,"-f",file[0],sizeof(file[0]),&flg);
     56:   if (flg) {
     57:     PetscStrcpy(file[1],file[0]);
     58:     preload = PETSC_FALSE;
     59:   } else {
     60:     PetscOptionsGetString(NULL,NULL,"-f0",file[0],sizeof(file[0]),&flg);
     61:     if (!flg) SETERRQ(PETSC_COMM_WORLD,PETSC_ERR_USER_INPUT,"Must indicate binary file with the -f0 or -f option");
     62:     PetscOptionsGetString(NULL,NULL,"-f1",file[1],sizeof(file[1]),&flg);
     63:     if (!flg) preload = PETSC_FALSE;   /* don't bother with second system */
     64:   }
     65:   PetscOptionsGetEnum(NULL,NULL,"-rhs",RHSTypes,(PetscEnum*)&rhstype,NULL);

     67:   /*
     68:     To use preloading, one usually has code like the following:

     70:     PetscPreLoadBegin(preload,"first stage);
     71:       lines of code
     72:     PetscPreLoadStage("second stage");
     73:       lines of code
     74:     PetscPreLoadEnd();

     76:     The two macro PetscPreLoadBegin() and PetscPreLoadEnd() implicitly form a
     77:     loop with maximal two iterations, depending whether preloading is turned on or
     78:     not. If it is, either through the preload arg of PetscPreLoadBegin or through
     79:     -preload command line, the trip count is 2, otherwise it is 1. One can use the
     80:     predefined variable PetscPreLoadIt within the loop body to get the current
     81:     iteration number, which is 0 or 1. If preload is turned on, the runtime doesn't
     82:     do profiling for the first iteration, but it will do profiling for the second
     83:     iteration instead.

     85:     One can solve a small system in the first iteration and a large system in
     86:     the second iteration. This process preloads the instructions with the small
     87:     system so that more accurate performance monitoring (via -log_view) can be done
     88:     with the large one (that actually is the system of interest).

     90:     But in this example, we turned off preloading and duplicated the code for
     91:     the large system. In general, it is a bad practice and one should not duplicate
     92:     code. We do that because we want to show profiling stages for both the small
     93:     system and the large system.
     94:   */
     95:   PetscPreLoadBegin(preload,"Load System 0");

     97:   /*=========================
     98:       solve a small system
     99:     =========================*/

    101:   /* open binary file. Note that we use FILE_MODE_READ to indicate reading from this file */
    102:   PetscViewerBinaryOpen(PETSC_COMM_WORLD,file[0],FILE_MODE_READ,&viewer);

    104:   /* load the matrix and vector; then destroy the viewer */
    105:   MatCreate(PETSC_COMM_WORLD,&A);
    106:   MatSetFromOptions(A);
    107:   MatLoad(A,viewer);
    108:   switch (rhstype) {
    109:   case RHS_FILE:
    110:     /* Vectors in the file might a different size than the matrix so we need a
    111:      * Vec whose size hasn't been set yet.  It'll get fixed below.  Otherwise we
    112:      * can create the correct size Vec. */
    113:     VecCreate(PETSC_COMM_WORLD,&b);
    114:     VecLoad(b,viewer);
    115:     break;
    116:   case RHS_ONE:
    117:     MatCreateVecs(A,&b,NULL);
    118:     VecSet(b,1.0);
    119:     break;
    120:   case RHS_RANDOM:
    121:     MatCreateVecs(A,&b,NULL);
    122:     VecSetRandom(b,NULL);
    123:     break;
    124:   }
    125:   PetscViewerDestroy(&viewer);

    127:   /* if the loaded matrix is larger than the vector (due to being padded
    128:      to match the block size of the system), then create a new padded vector
    129:    */
    130:   MatGetLocalSize(A,NULL,&n1);
    131:   VecGetLocalSize(b,&n2);
    132:   same = (n1 == n2)? PETSC_TRUE : PETSC_FALSE;
    133:   MPIU_Allreduce(MPI_IN_PLACE,&same,1,MPIU_BOOL,MPI_LAND,PETSC_COMM_WORLD);

    135:   if (!same) { /* create a new vector b by padding the old one */
    136:     VecCreate(PETSC_COMM_WORLD,&b2);
    137:     VecSetSizes(b2,n1,PETSC_DECIDE);
    138:     VecSetFromOptions(b2);
    139:     VecGetOwnershipRange(b,&start,NULL);
    140:     VecGetLocalSize(b,&len);
    141:     VecGetArrayRead(b,&val);
    142:     for (j=0; j<len; j++) {
    143:       idx = start+j;
    144:       VecSetValues(b2,1,&idx,val+j,INSERT_VALUES);
    145:     }
    146:     VecRestoreArrayRead(b,&val);
    147:     VecDestroy(&b);
    148:     VecAssemblyBegin(b2);
    149:     VecAssemblyEnd(b2);
    150:     b    = b2;
    151:   }
    152:   VecDuplicate(b,&x);

    154:   PetscPreLoadStage("KSPSetUp 0");
    155:   KSPCreate(PETSC_COMM_WORLD,&ksp);
    156:   KSPSetOperators(ksp,A,A);
    157:   KSPSetFromOptions(ksp);

    159:   /*
    160:     Here we explicitly call KSPSetUp() and KSPSetUpOnBlocks() to
    161:     enable more precise profiling of setting up the preconditioner.
    162:     These calls are optional, since both will be called within
    163:     KSPSolve() if they haven't been called already.
    164:   */
    165:   KSPSetUp(ksp);
    166:   KSPSetUpOnBlocks(ksp);

    168:   PetscPreLoadStage("KSPSolve 0");
    169:   if (trans) {KSPSolveTranspose(ksp,b,x);}
    170:   else       {KSPSolve(ksp,b,x);}

    172:   KSPGetTotalIterations(ksp,&its);
    173:   PetscPrintf(PETSC_COMM_WORLD,"Number of iterations = %d\n",its);

    175:   KSPGetResidualNorm(ksp,&norm);
    176:   if (norm < 1.e-12) {
    177:     PetscPrintf(PETSC_COMM_WORLD,"Residual norm < 1.e-12\n");
    178:   } else {
    179:     PetscPrintf(PETSC_COMM_WORLD,"Residual norm %e\n",(double)norm);
    180:   }

    182:   KSPDestroy(&ksp);
    183:   MatDestroy(&A);
    184:   VecDestroy(&x);
    185:   VecDestroy(&b);

    187:   /*=========================
    188:     solve a large system
    189:     =========================*/
    190:   /* the code is duplicated. Bad practice. See comments above */
    191:   PetscPreLoadStage("Load System 1");
    192:   PetscViewerBinaryOpen(PETSC_COMM_WORLD,file[1],FILE_MODE_READ,&viewer);

    194:   /* load the matrix and vector; then destroy the viewer */
    195:   MatCreate(PETSC_COMM_WORLD,&A);
    196:   MatSetFromOptions(A);
    197:   MatLoad(A,viewer);
    198:   switch (rhstype) {
    199:   case RHS_FILE:
    200:     /* Vectors in the file might a different size than the matrix so we need a
    201:      * Vec whose size hasn't been set yet.  It'll get fixed below.  Otherwise we
    202:      * can create the correct size Vec. */
    203:     VecCreate(PETSC_COMM_WORLD,&b);
    204:     VecLoad(b,viewer);
    205:     break;
    206:   case RHS_ONE:
    207:     MatCreateVecs(A,&b,NULL);
    208:     VecSet(b,1.0);
    209:     break;
    210:   case RHS_RANDOM:
    211:     MatCreateVecs(A,&b,NULL);
    212:     VecSetRandom(b,NULL);
    213:     break;
    214:   }
    215:   PetscViewerDestroy(&viewer);

    217:   MatGetLocalSize(A,NULL,&n1);
    218:   VecGetLocalSize(b,&n2);
    219:   same = (n1 == n2)? PETSC_TRUE : PETSC_FALSE;
    220:   MPIU_Allreduce(MPI_IN_PLACE,&same,1,MPIU_BOOL,MPI_LAND,PETSC_COMM_WORLD);

    222:   if (!same) { /* create a new vector b by padding the old one */
    223:     VecCreate(PETSC_COMM_WORLD,&b2);
    224:     VecSetSizes(b2,n1,PETSC_DECIDE);
    225:     VecSetFromOptions(b2);
    226:     VecGetOwnershipRange(b,&start,NULL);
    227:     VecGetLocalSize(b,&len);
    228:     VecGetArrayRead(b,&val);
    229:     for (j=0; j<len; j++) {
    230:       idx = start+j;
    231:       VecSetValues(b2,1,&idx,val+j,INSERT_VALUES);
    232:     }
    233:     VecRestoreArrayRead(b,&val);
    234:     VecDestroy(&b);
    235:     VecAssemblyBegin(b2);
    236:     VecAssemblyEnd(b2);
    237:     b    = b2;
    238:   }
    239:   VecDuplicate(b,&x);

    241:   PetscPreLoadStage("KSPSetUp 1");
    242:   KSPCreate(PETSC_COMM_WORLD,&ksp);
    243:   KSPSetOperators(ksp,A,A);
    244:   KSPSetFromOptions(ksp);
    245:   /*
    246:     Here we explicitly call KSPSetUp() and KSPSetUpOnBlocks() to
    247:     enable more precise profiling of setting up the preconditioner.
    248:     These calls are optional, since both will be called within
    249:     KSPSolve() if they haven't been called already.
    250:   */
    251:   KSPSetUp(ksp);
    252:   KSPSetUpOnBlocks(ksp);

    254:   PetscPreLoadStage("KSPSolve 1");
    255:   if (trans) {KSPSolveTranspose(ksp,b,x);}
    256:   else       {KSPSolve(ksp,b,x);}

    258:   KSPGetTotalIterations(ksp,&its);
    259:   PetscPrintf(PETSC_COMM_WORLD,"Number of iterations = %d\n",its);

    261:   KSPGetResidualNorm(ksp,&norm);
    262:   if (norm < 1.e-12) {
    263:     PetscPrintf(PETSC_COMM_WORLD,"Residual norm < 1.e-12\n");
    264:   } else {
    265:     PetscPrintf(PETSC_COMM_WORLD,"Residual norm %e\n",(double)norm);
    266:   }

    268:   KSPDestroy(&ksp);
    269:   MatDestroy(&A);
    270:   VecDestroy(&x);
    271:   VecDestroy(&b);
    272:   PetscPreLoadEnd();
    273:   /*
    274:      Always call PetscFinalize() before exiting a program.  This routine
    275:        - finalizes the PETSc libraries as well as MPI
    276:        - provides summary and diagnostic information if certain runtime
    277:          options are chosen (e.g., -log_view).
    278:   */
    279:   PetscFinalize();
    280:   return ierr;
    281: }

    283: /*TEST

    285:    test:
    286:       TODO: Matrix row/column sizes are not compatible with block size
    287:       suffix: 1
    288:       nsize: 4
    289:       output_file: output/ex10_1.out
    290:       requires: datafilespath double !complex !define(PETSC_USE_64BIT_INDICES)
    291:       args: -f0 ${DATAFILESPATH}/matrices/medium -f1 ${DATAFILESPATH}/matrices/arco6 -ksp_gmres_classicalgramschmidt -mat_type baij -matload_block_size 3 -pc_type bjacobi

    293:    test:
    294:       TODO: Matrix row/column sizes are not compatible with block size
    295:       suffix: 2
    296:       nsize: 4
    297:       output_file: output/ex10_2.out
    298:       requires: datafilespath double !complex !define(PETSC_USE_64BIT_INDICES)
    299:       args: -f0 ${DATAFILESPATH}/matrices/medium -f1 ${DATAFILESPATH}/matrices/arco6 -ksp_gmres_classicalgramschmidt -mat_type baij -matload_block_size 3 -pc_type bjacobi -trans

    301: TEST*/