Date: 2026-03-09T09:12:24+00:00

Actual source code: gun.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: */
     10: /*
     11:    This example implements one of the problems found at
     12:        NLEVP: A Collection of Nonlinear Eigenvalue Problems,
     13:        The University of Manchester.
     14:    The details of the collection can be found at:
     15:        [1] T. Betcke et al., "NLEVP: A Collection of Nonlinear Eigenvalue
     16:            Problems", ACM Trans. Math. Software 39(2), Article 7, 2013.

     18:    The gun problem arises from model of a radio-frequency gun cavity, with
     19:    the complex nonlinear function
     20:    T(lambda) = K-lambda*M+i*lambda^(1/2)*W1+i*(lambda-108.8774^2)^(1/2)*W2

     22:    Data files can be downloaded from https://gitlab.com/slepc/datafiles
     23: */

     25: static char help[] = "Radio-frequency gun cavity.\n\n"
     26:   "The command line options are:\n"
     27:   "-K <filename1> -M <filename2> -W1 <filename3> -W2 <filename4>, where filename1,..,filename4 are files containing the matrices in PETSc binary form defining the GUN problem.\n\n";

     29: #include <slepcnep.h>

     31: #define NMAT 4
     32: #define SIGMA 108.8774

     34: int main(int argc,char **argv)
     35: {
     36:   Mat            A[NMAT];         /* problem matrices */
     37:   FN             f[NMAT];         /* functions to define the nonlinear operator */
     38:   FN             ff[2];           /* auxiliary functions to define the nonlinear operator */
     39:   NEP            nep;             /* nonlinear eigensolver context */
     40:   PetscBool      terse,flg;
     41:   const char*    string[NMAT]={"-K","-M","-W1","-W2"};
     42:   char           filename[PETSC_MAX_PATH_LEN];
     43:   PetscScalar    numer[2],sigma;
     44:   PetscInt       i;
     45:   PetscViewer    viewer;

     47:   PetscFunctionBeginUser;
     48:   PetscCall(SlepcInitialize(&argc,&argv,NULL,help));

     50:   PetscCall(PetscPrintf(PETSC_COMM_WORLD,"GUN problem\n\n"));
     51: #if !defined(PETSC_USE_COMPLEX)
     52:   SETERRQ(PETSC_COMM_WORLD,PETSC_ERR_SUP,"This example requires complex scalars!");
     53: #endif

     55:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
     56:                        Load the problem matrices
     57:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

     59:   for (i=0;i<NMAT;i++) {
     60:     PetscCall(PetscOptionsGetString(NULL,NULL,string[i],filename,sizeof(filename),&flg));
     61:     PetscCheck(flg,PETSC_COMM_WORLD,PETSC_ERR_USER_INPUT,"Must indicate a filename with the %s option",string[i]);
     62:     PetscCall(PetscViewerBinaryOpen(PETSC_COMM_WORLD,filename,FILE_MODE_READ,&viewer));
     63:     PetscCall(MatCreate(PETSC_COMM_WORLD,&A[i]));
     64:     PetscCall(MatSetFromOptions(A[i]));
     65:     PetscCall(MatLoad(A[i],viewer));
     66:     PetscCall(PetscViewerDestroy(&viewer));
     67:   }

     69:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
     70:                        Create the problem functions
     71:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

     73:   /* f1=1 */
     74:   PetscCall(FNCreate(PETSC_COMM_WORLD,&f[0]));
     75:   PetscCall(FNSetType(f[0],FNRATIONAL));
     76:   numer[0] = 1.0;
     77:   PetscCall(FNRationalSetNumerator(f[0],1,numer));

     79:   /* f2=-lambda */
     80:   PetscCall(FNCreate(PETSC_COMM_WORLD,&f[1]));
     81:   PetscCall(FNSetType(f[1],FNRATIONAL));
     82:   numer[0] = -1.0; numer[1] = 0.0;
     83:   PetscCall(FNRationalSetNumerator(f[1],2,numer));

     85:   /* f3=i*sqrt(lambda) */
     86:   PetscCall(FNCreate(PETSC_COMM_WORLD,&f[2]));
     87:   PetscCall(FNSetType(f[2],FNSQRT));
     88:   PetscCall(FNSetScale(f[2],1.0,PETSC_i));

     90:   /* f4=i*sqrt(lambda-sigma^2) */
     91:   sigma = SIGMA*SIGMA;
     92:   PetscCall(FNCreate(PETSC_COMM_WORLD,&ff[0]));
     93:   PetscCall(FNSetType(ff[0],FNSQRT));
     94:   PetscCall(FNCreate(PETSC_COMM_WORLD,&ff[1]));
     95:   PetscCall(FNSetType(ff[1],FNRATIONAL));
     96:   numer[0] = 1.0; numer[1] = -sigma;
     97:   PetscCall(FNRationalSetNumerator(ff[1],2,numer));
     98:   PetscCall(FNCreate(PETSC_COMM_WORLD,&f[3]));
     99:   PetscCall(FNSetType(f[3],FNCOMBINE));
    100:   PetscCall(FNCombineSetChildren(f[3],FN_COMBINE_COMPOSE,ff[1],ff[0]));
    101:   PetscCall(FNSetScale(f[3],1.0,PETSC_i));

    103:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
    104:                 Create the eigensolver and solve the problem
    105:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

    107:   PetscCall(NEPCreate(PETSC_COMM_WORLD,&nep));
    108:   PetscCall(NEPSetSplitOperator(nep,4,A,f,UNKNOWN_NONZERO_PATTERN));
    109:   PetscCall(NEPSetFromOptions(nep));

    111:   PetscCall(NEPSolve(nep));

    113:   /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
    114:                     Display solution and clean up
    115:      - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

    117:   /* show detailed info unless -terse option is given by user */
    118:   PetscCall(PetscOptionsHasName(NULL,NULL,"-terse",&terse));
    119:   if (terse) PetscCall(NEPErrorView(nep,NEP_ERROR_RELATIVE,NULL));
    120:   else {
    121:     PetscCall(PetscViewerPushFormat(PETSC_VIEWER_STDOUT_WORLD,PETSC_VIEWER_ASCII_INFO_DETAIL));
    122:     PetscCall(NEPConvergedReasonView(nep,PETSC_VIEWER_STDOUT_WORLD));
    123:     PetscCall(NEPErrorView(nep,NEP_ERROR_RELATIVE,PETSC_VIEWER_STDOUT_WORLD));
    124:     PetscCall(PetscViewerPopFormat(PETSC_VIEWER_STDOUT_WORLD));
    125:   }
    126:   PetscCall(NEPDestroy(&nep));
    127:   for (i=0;i<NMAT;i++) {
    128:     PetscCall(MatDestroy(&A[i]));
    129:     PetscCall(FNDestroy(&f[i]));
    130:   }
    131:   for (i=0;i<2;i++) PetscCall(FNDestroy(&ff[i]));
    132:   PetscCall(SlepcFinalize());
    133:   return 0;
    134: }

    136: /*TEST

    138:    build:
    139:       requires: complex

    141:    test:
    142:       suffix: 1
    143:       args: -K ${DATAFILESPATH}/matrices/complex/gun_K.petsc -M ${DATAFILESPATH}/matrices/complex/gun_M.petsc -W1 ${DATAFILESPATH}/matrices/complex/gun_W1.petsc -W2 ${DATAFILESPATH}/matrices/complex/gun_W2.petsc -nep_type nleigs -rg_type polygon -rg_polygon_vertices 12500-1i,120500-1i,120500+30000i,70000+30000i -nep_target 65000 -nep_nev 24 -terse
    144:       requires: double complex datafilespath !defined(PETSC_USE_64BIT_INDICES) !defined(PETSCTEST_VALGRIND)
    145:       timeoutfactor: 10

    147: TEST*/