Actual source code: ex1f90.F90

slepc-3.11.2 2019-07-30
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  1: !
  2: !  - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
  3: !  SLEPc - Scalable Library for Eigenvalue Problem Computations
  4: !  Copyright (c) 2002-2019, 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:       implicit none

 26: ! - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 27: !     Declarations
 28: ! - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 29: !
 30: !  Variables:
 31: !     A      operator matrix
 32: !     eps    eigenproblem solver context

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

 45: ! - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 46: !     Beginning of program
 47: ! - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

 49:       one = 1
 50:       two = 2
 51:       three = 3
 52:       call SlepcInitialize(PETSC_NULL_CHARACTER,ierr)
 53:       if (ierr .ne. 0) then
 54:         print*,'SlepcInitialize failed'
 55:         stop
 56:       endif
 57:       call MPI_Comm_rank(PETSC_COMM_WORLD,rank,ierr);CHKERRA(ierr)
 58:       n = 30
 59:       call PetscOptionsGetInt(PETSC_NULL_OPTIONS,PETSC_NULL_CHARACTER,'-n',n,flg,ierr);CHKERRA(ierr)

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

 66: ! - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
 67: !     Compute the operator matrix that defines the eigensystem, Ax=kx
 68: ! - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

 70:       call MatCreate(PETSC_COMM_WORLD,A,ierr);CHKERRA(ierr)
 71:       call MatSetSizes(A,PETSC_DECIDE,PETSC_DECIDE,n,n,ierr);CHKERRA(ierr)
 72:       call MatSetFromOptions(A,ierr);CHKERRA(ierr)
 73:       call MatSetUp(A,ierr);CHKERRA(ierr)

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

105:       call MatAssemblyBegin(A,MAT_FINAL_ASSEMBLY,ierr);CHKERRA(ierr)
106:       call MatAssemblyEnd(A,MAT_FINAL_ASSEMBLY,ierr);CHKERRA(ierr)

108: ! - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
109: !     Create the eigensolver and display info
110: ! - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

112: !     ** Create eigensolver context
113:       call EPSCreate(PETSC_COMM_WORLD,eps,ierr);CHKERRA(ierr)

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

119: !     ** Set solver parameters at runtime
120:       call EPSSetFromOptions(eps,ierr);CHKERRA(ierr)

122: ! - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
123: !     Solve the eigensystem
124: ! - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

126:       call EPSSolve(eps,ierr);CHKERRA(ierr)

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

140: ! - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
141: !     Display solution and clean up
142: ! - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

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

157:       call SlepcFinalize(ierr)
158:       end

160: !/*TEST
161: !
162: !   test:
163: !      suffix: 1
164: !      args: -eps_nev 4 -terse
165: !
166: !TEST*/