Date: 2026-01-20T11:35:30+00:00

Actual source code: test3.c

      1: /*
      2:    - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
      3:    SLEPc - Scalable Library for Eigenvalue Problem Computations
      4:    Copyright (c) 2002-, Universitat Politecnica de Valencia, Spain

      6:    This file is part of SLEPc.
      7:    SLEPc is distributed under a 2-clause BSD license (see LICENSE).
      8:    - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
      9: */

     11: static char help[] = "Test matrix exponential.\n\n";

     13: #include <slepcfn.h>

     15: /*
     16:    Compute matrix exponential B = expm(A)
     17:  */
     18: PetscErrorCode TestMatExp(FN fn,Mat A,PetscViewer viewer,PetscBool verbose,PetscBool inplace,PetscBool checkerror)
     19: {
     20:   PetscScalar    tau,eta;
     21:   PetscBool      set,flg;
     22:   PetscInt       n;
     23:   Mat            F,R,Finv,Acopy;
     24:   Vec            v,f0;
     25:   FN             finv;
     26:   PetscReal      nrm,nrmf;

     28:   PetscFunctionBeginUser;
     29:   PetscCall(MatGetSize(A,&n,NULL));
     30:   PetscCall(MatDuplicate(A,MAT_DO_NOT_COPY_VALUES,&F));
     31:   PetscCall(PetscObjectSetName((PetscObject)F,"F"));
     32:   /* compute matrix exponential */
     33:   if (inplace) {
     34:     PetscCall(MatCopy(A,F,SAME_NONZERO_PATTERN));
     35:     PetscCall(MatIsHermitianKnown(A,&set,&flg));
     36:     if (set && flg) PetscCall(MatSetOption(F,MAT_HERMITIAN,PETSC_TRUE));
     37:     PetscCall(FNEvaluateFunctionMat(fn,F,NULL));
     38:   } else {
     39:     PetscCall(MatDuplicate(A,MAT_COPY_VALUES,&Acopy));
     40:     PetscCall(FNEvaluateFunctionMat(fn,A,F));
     41:     /* check that A has not been modified */
     42:     PetscCall(MatAXPY(Acopy,-1.0,A,SAME_NONZERO_PATTERN));
     43:     PetscCall(MatNorm(Acopy,NORM_1,&nrm));
     44:     if (nrm>100*PETSC_MACHINE_EPSILON) PetscCall(PetscPrintf(PETSC_COMM_WORLD,"Warning: the input matrix has changed by %g\n",(double)nrm));
     45:     PetscCall(MatDestroy(&Acopy));
     46:   }
     47:   if (verbose) {
     48:     PetscCall(PetscPrintf(PETSC_COMM_WORLD,"Matrix A - - - - - - - -\n"));
     49:     PetscCall(MatView(A,viewer));
     50:     PetscCall(PetscPrintf(PETSC_COMM_WORLD,"Computed expm(A) - - - - - - -\n"));
     51:     PetscCall(MatView(F,viewer));
     52:   }
     53:   /* print matrix norm for checking */
     54:   PetscCall(MatNorm(F,NORM_1,&nrmf));
     55:   PetscCall(PetscPrintf(PETSC_COMM_WORLD,"The 1-norm of f(A) is %g\n",(double)nrmf));
     56:   if (checkerror) {
     57:     PetscCall(MatDuplicate(A,MAT_DO_NOT_COPY_VALUES,&Finv));
     58:     PetscCall(PetscObjectSetName((PetscObject)Finv,"Finv"));
     59:     PetscCall(FNGetScale(fn,&tau,&eta));
     60:     /* compute inverse exp(-tau*A)/eta */
     61:     PetscCall(FNCreate(PETSC_COMM_WORLD,&finv));
     62:     PetscCall(FNSetType(finv,FNEXP));
     63:     PetscCall(FNSetFromOptions(finv));
     64:     PetscCall(FNSetScale(finv,-tau,1.0/eta));
     65:     if (inplace) {
     66:       PetscCall(MatCopy(A,Finv,SAME_NONZERO_PATTERN));
     67:       PetscCall(MatIsHermitianKnown(A,&set,&flg));
     68:       if (set && flg) PetscCall(MatSetOption(Finv,MAT_HERMITIAN,PETSC_TRUE));
     69:       PetscCall(FNEvaluateFunctionMat(finv,Finv,NULL));
     70:     } else PetscCall(FNEvaluateFunctionMat(finv,A,Finv));
     71:     PetscCall(FNDestroy(&finv));
     72:     /* check error ||F*Finv-I||_F */
     73:     PetscCall(MatMatMult(F,Finv,MAT_INITIAL_MATRIX,PETSC_DEFAULT,&R));
     74:     PetscCall(MatShift(R,-1.0));
     75:     PetscCall(MatNorm(R,NORM_FROBENIUS,&nrm));
     76:     if (nrm<100*PETSC_MACHINE_EPSILON) PetscCall(PetscPrintf(PETSC_COMM_WORLD,"||exp(A)*exp(-A)-I||_F < 100*eps\n"));
     77:     else PetscCall(PetscPrintf(PETSC_COMM_WORLD,"||exp(A)*exp(-A)-I||_F = %g\n",(double)nrm));
     78:     PetscCall(MatDestroy(&R));
     79:     PetscCall(MatDestroy(&Finv));
     80:   }
     81:   /* check FNEvaluateFunctionMatVec() */
     82:   PetscCall(MatCreateVecs(A,&v,&f0));
     83:   PetscCall(MatGetColumnVector(F,f0,0));
     84:   PetscCall(FNEvaluateFunctionMatVec(fn,A,v));
     85:   PetscCall(VecAXPY(v,-1.0,f0));
     86:   PetscCall(VecNorm(v,NORM_2,&nrm));
     87:   if (nrm/nrmf>100*PETSC_MACHINE_EPSILON) PetscCall(PetscPrintf(PETSC_COMM_WORLD,"Warning: the norm of f(A)*e_1-v is %g\n",(double)nrm));
     88:   PetscCall(MatDestroy(&F));
     89:   PetscCall(VecDestroy(&v));
     90:   PetscCall(VecDestroy(&f0));
     91:   PetscFunctionReturn(PETSC_SUCCESS);
     92: }

     94: int main(int argc,char **argv)
     95: {
     96:   FN             fn;
     97:   Mat            A=NULL;
     98:   PetscInt       i,j,n=10;
     99:   PetscScalar    *As;
    100:   PetscViewer    viewer;
    101:   PetscBool      verbose,inplace,checkerror,matcuda;

    103:   PetscFunctionBeginUser;
    104:   PetscCall(SlepcInitialize(&argc,&argv,NULL,help));
    105:   PetscCall(PetscOptionsGetInt(NULL,NULL,"-n",&n,NULL));
    106:   PetscCall(PetscOptionsHasName(NULL,NULL,"-verbose",&verbose));
    107:   PetscCall(PetscOptionsHasName(NULL,NULL,"-inplace",&inplace));
    108:   PetscCall(PetscOptionsHasName(NULL,NULL,"-checkerror",&checkerror));
    109:   PetscCall(PetscOptionsHasName(NULL,NULL,"-matcuda",&matcuda));
    110:   PetscCall(PetscPrintf(PETSC_COMM_WORLD,"Matrix exponential, n=%" PetscInt_FMT ".\n",n));

    112:   /* Create exponential function object */
    113:   PetscCall(FNCreate(PETSC_COMM_WORLD,&fn));
    114:   PetscCall(FNSetType(fn,FNEXP));
    115:   PetscCall(FNSetFromOptions(fn));

    117:   /* Set up viewer */
    118:   PetscCall(PetscViewerASCIIGetStdout(PETSC_COMM_WORLD,&viewer));
    119:   PetscCall(FNView(fn,viewer));
    120:   if (verbose) PetscCall(PetscViewerPushFormat(viewer,PETSC_VIEWER_ASCII_MATLAB));

    122:   /* Create matrices */
    123:   if (matcuda) {
    124: #if defined(PETSC_HAVE_CUDA)
    125:     PetscCall(MatCreateSeqDenseCUDA(PETSC_COMM_SELF,n,n,NULL,&A));
    126: #endif
    127:   } else PetscCall(MatCreateSeqDense(PETSC_COMM_SELF,n,n,NULL,&A));
    128:   PetscCall(PetscObjectSetName((PetscObject)A,"A"));

    130:   /* Fill A with a symmetric Toeplitz matrix */
    131:   PetscCall(MatDenseGetArray(A,&As));
    132:   for (i=0;i<n;i++) As[i+i*n]=2.0;
    133:   for (j=1;j<3;j++) {
    134:     for (i=0;i<n-j;i++) {
    135:       As[i+(i+j)*n]=1.0;
    136:       As[(i+j)+i*n]=1.0;
    137:     }
    138:   }
    139:   PetscCall(MatDenseRestoreArray(A,&As));
    140:   PetscCall(MatSetOption(A,MAT_HERMITIAN,PETSC_TRUE));
    141:   PetscCall(TestMatExp(fn,A,viewer,verbose,inplace,checkerror));

    143:   /* Repeat with non-symmetric A */
    144:   PetscCall(MatDenseGetArray(A,&As));
    145:   for (j=1;j<3;j++) {
    146:     for (i=0;i<n-j;i++) As[(i+j)+i*n]=-1.0;
    147:   }
    148:   PetscCall(MatDenseRestoreArray(A,&As));
    149:   PetscCall(MatSetOption(A,MAT_HERMITIAN,PETSC_FALSE));
    150:   PetscCall(TestMatExp(fn,A,viewer,verbose,inplace,checkerror));

    152:   PetscCall(MatDestroy(&A));
    153:   PetscCall(FNDestroy(&fn));
    154:   PetscCall(SlepcFinalize());
    155:   return 0;
    156: }

    158: /*TEST

    160:    testset:
    161:       filter: grep -v "computing matrix functions"
    162:       output_file: output/test3_1.out
    163:       test:
    164:          suffix: 1
    165:          args: -fn_method {{0 1}}
    166:       test:
    167:          suffix: 1_subdiagonalpade
    168:          args: -fn_method {{2 3}}
    169:          requires: c99_complex !single
    170:       test:
    171:          suffix: 1_cuda
    172:          args: -fn_method 1 -matcuda
    173:          requires: cuda !magma
    174:       test:
    175:          suffix: 1_magma
    176:          args: -fn_method {{0 1 2 3}} -matcuda
    177:          requires: cuda magma
    178:       test:
    179:          suffix: 2
    180:          args: -inplace -fn_method{{0 1}}
    181:       test:
    182:          suffix: 2_subdiagonalpade
    183:          args: -inplace -fn_method{{2 3}}
    184:          requires: c99_complex !single
    185:       test:
    186:          suffix: 2_cuda
    187:          args: -inplace -fn_method 1 -matcuda
    188:          requires: cuda !magma
    189:       test:
    190:          suffix: 2_magma
    191:          args: -inplace -fn_method {{0 1 2 3}} -matcuda
    192:          requires: cuda magma

    194:    testset:
    195:       args: -fn_scale 0.1
    196:       filter: grep -v "computing matrix functions"
    197:       output_file: output/test3_3.out
    198:       test:
    199:          suffix: 3
    200:          args: -fn_method {{0 1}}
    201:       test:
    202:         suffix: 3_subdiagonalpade
    203:         args: -fn_method {{2 3}}
    204:         requires: c99_complex !single

    206:    testset:
    207:       args: -n 120 -fn_scale 0.6,1.5
    208:       filter: grep -v "computing matrix functions"
    209:       output_file: output/test3_4.out
    210:       test:
    211:          suffix: 4
    212:          args: -fn_method {{0 1}}
    213:          requires: !single
    214:       test:
    215:         suffix: 4_subdiagonalpade
    216:         args: -fn_method {{2 3}}
    217:         requires: c99_complex !single

    219:    test:
    220:       suffix: 5
    221:       args: -fn_scale 30 -fn_method {{2 3}}
    222:       filter: grep -v "computing matrix functions"
    223:       requires: c99_complex !single
    224:       output_file: output/test3_5.out

    226:    test:
    227:       suffix: 6
    228:       args: -fn_scale 1e-9 -fn_method {{2 3}}
    229:       filter: grep -v "computing matrix functions"
    230:       requires: c99_complex !single
    231:       output_file: output/test3_6.out

    233: TEST*/