Date: 2022-10-01T06:40:04+00:00

Actual source code: ex1f90.F90
slepc-3.18.0 2022-10-01
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      1: !
      2: !  - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
      3: !  SLEPc - Scalable Library for Eigenvalue Problem Computations
      4: !  Copyright (c) 2002-, Universitat Politecnica de Valencia, Spain
      5: !
      6: !  This file is part of SLEPc.
      7: !  SLEPc is distributed under a 2-clause BSD license (see LICENSE).
      8: !  - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
      9: !
     10: !  Program usage: mpiexec -n <np> ./ex1f90 [-help] [-n <n>] [all SLEPc options]
     11: !
     12: !  Description: Simple example that solves an eigensystem with the EPS object.
     13: !  The standard symmetric eigenvalue problem to be solved corresponds to the
     14: !  Laplacian operator in 1 dimension.
     15: !
     16: !  The command line options are:
     17: !    -n <n>, where <n> = number of grid points = matrix size
     18: !
     19: ! ----------------------------------------------------------------------
     20: !
     21:       program main
     22: #include <slepc/finclude/slepceps.h>
     23:       use slepceps
     24:       use,intrinsic :: iso_c_binding
     25:       implicit none

     27: ! - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
     28: !     Declarations
     29: ! - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
     30: !
     31: !  Variables:
     32: !     A      operator matrix
     33: !     eps    eigenproblem solver context

     35:       Mat            A
     36:       EPS            eps
     37:       EPSType        tname
     38:       PetscInt       n, i, Istart, Iend, one, two, three
     39:       PetscInt       nev
     40:       PetscInt       row(1), col(3)
     41:       PetscMPIInt    rank
     42:       PetscErrorCode ierr
     43:       PetscBool      flg, terse
     44:       PetscScalar    val(3)

     46: ! - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
     47: !     Beginning of program
     48: ! - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

     50:       one = 1
     51:       two = 2
     52:       three = 3
     53:       PetscCallA(SlepcInitialize(PETSC_NULL_CHARACTER,"ex1f90 test"//c_new_line,ierr))
     54:       if (ierr .ne. 0) then
     55:         print*,'SlepcInitialize failed'
     56:         stop
     57:       endif
     58:       PetscCallMPIA(MPI_Comm_rank(PETSC_COMM_WORLD,rank,ierr))
     59:       n = 30
     60:       PetscCallA(PetscOptionsGetInt(PETSC_NULL_OPTIONS,PETSC_NULL_CHARACTER,'-n',n,flg,ierr))

     62:       if (rank .eq. 0) then
     63:         write(*,100) n
     64:       endif
     65:  100  format (/'1-D Laplacian Eigenproblem, n =',I4,' (Fortran)')

     67: ! - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
     68: !     Compute the operator matrix that defines the eigensystem, Ax=kx
     69: ! - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

     71:       PetscCallA(MatCreate(PETSC_COMM_WORLD,A,ierr))
     72:       PetscCallA(MatSetSizes(A,PETSC_DECIDE,PETSC_DECIDE,n,n,ierr))
     73:       PetscCallA(MatSetFromOptions(A,ierr))
     74:       PetscCallA(MatSetUp(A,ierr))

     76:       PetscCallA(MatGetOwnershipRange(A,Istart,Iend,ierr))
     77:       if (Istart .eq. 0) then
     78:         row(1) = 0
     79:         col(1) = 0
     80:         col(2) = 1
     81:         val(1) =  2.0
     82:         val(2) = -1.0
     83:         PetscCallA(MatSetValues(A,one,row,two,col,val,INSERT_VALUES,ierr))
     84:         Istart = Istart+1
     85:       endif
     86:       if (Iend .eq. n) then
     87:         row(1) = n-1
     88:         col(1) = n-2
     89:         col(2) = n-1
     90:         val(1) = -1.0
     91:         val(2) =  2.0
     92:         PetscCallA(MatSetValues(A,one,row,two,col,val,INSERT_VALUES,ierr))
     93:         Iend = Iend-1
     94:       endif
     95:       val(1) = -1.0
     96:       val(2) =  2.0
     97:       val(3) = -1.0
     98:       do i=Istart,Iend-1
     99:         row(1) = i
    100:         col(1) = i-1
    101:         col(2) = i
    102:         col(3) = i+1
    103:         PetscCallA(MatSetValues(A,one,row,three,col,val,INSERT_VALUES,ierr))
    104:       enddo

    106:       PetscCallA(MatAssemblyBegin(A,MAT_FINAL_ASSEMBLY,ierr))
    107:       PetscCallA(MatAssemblyEnd(A,MAT_FINAL_ASSEMBLY,ierr))

    109: ! - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
    110: !     Create the eigensolver and display info
    111: ! - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

    113: !     ** Create eigensolver context
    114:       PetscCallA(EPSCreate(PETSC_COMM_WORLD,eps,ierr))

    116: !     ** Set operators. In this case, it is a standard eigenvalue problem
    117:       PetscCallA(EPSSetOperators(eps,A,PETSC_NULL_MAT,ierr))
    118:       PetscCallA(EPSSetProblemType(eps,EPS_HEP,ierr))

    120: !     ** Set solver parameters at runtime
    121:       PetscCallA(EPSSetFromOptions(eps,ierr))

    123: ! - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
    124: !     Solve the eigensystem
    125: ! - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

    127:       PetscCallA(EPSSolve(eps,ierr))

    129: !     ** Optional: Get some information from the solver and display it
    130:       PetscCallA(EPSGetType(eps,tname,ierr))
    131:       if (rank .eq. 0) then
    132:         write(*,120) tname
    133:       endif
    134:  120  format (' Solution method: ',A)
    135:       PetscCallA(EPSGetDimensions(eps,nev,PETSC_NULL_INTEGER,PETSC_NULL_INTEGER,ierr))
    136:       if (rank .eq. 0) then
    137:         write(*,130) nev
    138:       endif
    139:  130  format (' Number of requested eigenvalues:',I4)

    141: ! - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
    142: !     Display solution and clean up
    143: ! - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

    145: !     ** show detailed info unless -terse option is given by user
    146:       PetscCallA(PetscOptionsHasName(PETSC_NULL_OPTIONS,PETSC_NULL_CHARACTER,'-terse',terse,ierr))
    147:       if (terse) then
    148:         PetscCallA(EPSErrorView(eps,EPS_ERROR_RELATIVE,PETSC_NULL_VIEWER,ierr))
    149:       else
    150:         PetscCallA(PetscViewerPushFormat(PETSC_VIEWER_STDOUT_WORLD,PETSC_VIEWER_ASCII_INFO_DETAIL,ierr))
    151:         PetscCallA(EPSConvergedReasonView(eps,PETSC_VIEWER_STDOUT_WORLD,ierr))
    152:         PetscCallA(EPSErrorView(eps,EPS_ERROR_RELATIVE,PETSC_VIEWER_STDOUT_WORLD,ierr))
    153:         PetscCallA(PetscViewerPopFormat(PETSC_VIEWER_STDOUT_WORLD,ierr))
    154:       endif
    155:       PetscCallA(EPSDestroy(eps,ierr))
    156:       PetscCallA(MatDestroy(A,ierr))

    158:       PetscCallA(SlepcFinalize(ierr))
    159:       end

    161: !/*TEST
    162: !
    163: !   build:
    164: !      requires: defined(PETSC_USING_F2003) defined(PETSC_USING_F90FREEFORM)
    165: !
    166: !   test:
    167: !      args: -eps_nev 4 -terse
    168: !      filter: sed -e "s/3.83791/3.83792/"
    169: !
    170: !TEST*/