Actual source code: ex1f.F
slepc-3.20.1 2023-11-27
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> ./ex1f [-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: ! Notes:
20: ! - The free-form equivalent of this example is ex1f90.F90.
21: ! - Does not check errors, see ex1f90.F90 for error checking (recommended).
22: ! ----------------------------------------------------------------------
23: !
24: program main
25: #include <slepc/finclude/slepceps.h>
26: use slepceps
27: implicit none
29: ! - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
30: ! Declarations
31: ! - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
32: !
33: ! Variables:
34: ! A operator matrix
35: ! eps eigenproblem solver context
37: Mat A
38: EPS eps
39: EPSType tname
40: PetscReal tol, error
41: PetscScalar kr, ki
42: Vec xr, xi
43: PetscInt n, i, Istart, Iend
44: PetscInt nev, maxit, its, nconv
45: PetscInt col(3)
46: PetscInt i1,i2,i3
47: PetscMPIInt rank
48: PetscErrorCode ierr
49: PetscBool flg
50: PetscScalar value(3)
52: ! - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
53: ! Beginning of program
54: ! - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
56: call SlepcInitialize(PETSC_NULL_CHARACTER,ierr)
57: call MPI_Comm_rank(PETSC_COMM_WORLD,rank,ierr)
58: n = 30
59: call PetscOptionsGetInt(PETSC_NULL_OPTIONS,PETSC_NULL_CHARACTER, &
60: & '-n',n,flg,ierr)
62: if (rank .eq. 0) then
63: write(*,100) n
64: endif
65: 100 format (/'1-D Laplacian Eigenproblem, n =',I3,' (Fortran)')
67: ! - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
68: ! Compute the operator matrix that defines the eigensystem, Ax=kx
69: ! - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
71: call MatCreate(PETSC_COMM_WORLD,A,ierr)
72: call MatSetSizes(A,PETSC_DECIDE,PETSC_DECIDE,n,n,ierr)
73: call MatSetFromOptions(A,ierr)
74: call MatSetUp(A,ierr)
76: i1 = 1
77: i2 = 2
78: i3 = 3
79: call MatGetOwnershipRange(A,Istart,Iend,ierr)
80: if (Istart .eq. 0) then
81: i = 0
82: col(1) = 0
83: col(2) = 1
84: value(1) = 2.0
85: value(2) = -1.0
86: call MatSetValues(A,i1,i,i2,col,value,INSERT_VALUES,ierr)
87: Istart = Istart+1
88: endif
89: if (Iend .eq. n) then
90: i = n-1
91: col(1) = n-2
92: col(2) = n-1
93: value(1) = -1.0
94: value(2) = 2.0
95: call MatSetValues(A,i1,i,i2,col,value,INSERT_VALUES,ierr)
96: Iend = Iend-1
97: endif
98: value(1) = -1.0
99: value(2) = 2.0
100: value(3) = -1.0
101: do i=Istart,Iend-1
102: col(1) = i-1
103: col(2) = i
104: col(3) = i+1
105: call MatSetValues(A,i1,i,i3,col,value,INSERT_VALUES,ierr)
106: enddo
108: call MatAssemblyBegin(A,MAT_FINAL_ASSEMBLY,ierr)
109: call MatAssemblyEnd(A,MAT_FINAL_ASSEMBLY,ierr)
111: call MatCreateVecs(A,xr,xi,ierr)
113: ! - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
114: ! Create the eigensolver and display info
115: ! - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
117: ! ** Create eigensolver context
118: call EPSCreate(PETSC_COMM_WORLD,eps,ierr)
120: ! ** Set operators. In this case, it is a standard eigenvalue problem
121: call EPSSetOperators(eps,A,PETSC_NULL_MAT,ierr)
122: call EPSSetProblemType(eps,EPS_HEP,ierr)
124: ! ** Set solver parameters at runtime
125: call EPSSetFromOptions(eps,ierr)
127: ! - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
128: ! Solve the eigensystem
129: ! - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
131: call EPSSolve(eps,ierr)
132: call EPSGetIterationNumber(eps,its,ierr)
133: if (rank .eq. 0) then
134: write(*,110) its
135: endif
136: 110 format (/' Number of iterations of the method:',I4)
138: ! ** Optional: Get some information from the solver and display it
139: call EPSGetType(eps,tname,ierr)
140: if (rank .eq. 0) then
141: write(*,120) tname
142: endif
143: 120 format (' Solution method: ',A)
144: call EPSGetDimensions(eps,nev,PETSC_NULL_INTEGER, &
145: & PETSC_NULL_INTEGER,ierr)
146: if (rank .eq. 0) then
147: write(*,130) nev
148: endif
149: 130 format (' Number of requested eigenvalues:',I2)
150: call EPSGetTolerances(eps,tol,maxit,ierr)
151: if (rank .eq. 0) then
152: write(*,140) tol, maxit
153: endif
154: 140 format (' Stopping condition: tol=',1P,E11.4,', maxit=',I4)
156: ! - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
157: ! Display solution and clean up
158: ! - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
160: ! ** Get number of converged eigenpairs
161: call EPSGetConverged(eps,nconv,ierr)
162: if (rank .eq. 0) then
163: write(*,150) nconv
164: endif
165: 150 format (' Number of converged eigenpairs:',I2/)
167: ! ** Display eigenvalues and relative errors
168: if (nconv.gt.0) then
169: if (rank .eq. 0) then
170: write(*,*) ' k ||Ax-kx||/||kx||'
171: write(*,*) ' ----------------- ------------------'
172: endif
173: do i=0,nconv-1
174: ! ** Get converged eigenpairs: i-th eigenvalue is stored in kr
175: ! ** (real part) and ki (imaginary part)
176: call EPSGetEigenpair(eps,i,kr,ki,xr,xi,ierr)
178: ! ** Compute the relative error associated to each eigenpair
179: call EPSComputeError(eps,i,EPS_ERROR_RELATIVE,error,ierr)
180: if (rank .eq. 0) then
181: write(*,160) PetscRealPart(kr), error
182: endif
183: 160 format (1P,' ',E12.4,' ',E12.4)
185: enddo
186: if (rank .eq. 0) then
187: write(*,*)
188: endif
189: endif
191: ! ** Free work space
192: call EPSDestroy(eps,ierr)
193: call MatDestroy(A,ierr)
194: call VecDestroy(xr,ierr)
195: call VecDestroy(xi,ierr)
197: call SlepcFinalize(ierr)
198: end