! F12ASF Example Program Text
! Mark 30.0 Release. NAG Copyright 2024.
Module f12asfe_mod
! F12ASF Example Program Module:
! Parameters and User-defined Routines
! .. Use Statements ..
Use nag_library, Only: nag_wp
! .. Implicit None Statement ..
Implicit None
! .. Accessibility Statements ..
Private
Public :: mv
! .. Parameters ..
Complex (Kind=nag_wp), Parameter, Public :: four = (4.0_nag_wp, &
0.0_nag_wp)
Complex (Kind=nag_wp), Parameter, Public :: one = (1.0_nag_wp,0.0_nag_wp &
)
Complex (Kind=nag_wp), Parameter, Public :: six = (6.0_nag_wp,0.0_nag_wp &
)
Complex (Kind=nag_wp), Parameter, Public :: two = (2.0_nag_wp,0.0_nag_wp &
)
Integer, Parameter, Public :: imon = 1, licomm = 140, nerr = 6, &
nin = 5, nout = 6
Contains
Subroutine mv(nx,v,w)
! Compute the out-of--place matrix vector multiplication Y<---M*X,
! where M is mass matrix formed by using piecewise linear elements
! on [0,1].
! .. Use Statements ..
Use nag_library, Only: zscal
! .. Scalar Arguments ..
Integer, Intent (In) :: nx
! .. Array Arguments ..
Complex (Kind=nag_wp), Intent (In) :: v(nx*nx)
Complex (Kind=nag_wp), Intent (Out) :: w(nx*nx)
! .. Local Scalars ..
Complex (Kind=nag_wp) :: h
Integer :: j, n
! .. Intrinsic Procedures ..
Intrinsic :: cmplx
! .. Executable Statements ..
n = nx*nx
w(1) = (four*v(1)+v(2))/six
Do j = 2, n - 1
w(j) = (v(j-1)+four*v(j)+v(j+1))/six
End Do
w(n) = (v(n-1)+four*v(n))/six
h = one/cmplx(n+1,kind=nag_wp)
! The NAG name equivalent of zscal is f06gdf
Call zscal(n,h,w,1)
Return
End Subroutine mv
End Module f12asfe_mod
Program f12asfe
! F12ASF Example Main Program
! .. Use Statements ..
Use f12asfe_mod, Only: four, imon, licomm, mv, nerr, nin, nout, one, &
six, two
Use nag_library, Only: dznrm2, f12anf, f12apf, f12aqf, f12arf, f12asf, &
nag_wp, zgttrf, zgttrs
! .. Implicit None Statement ..
Implicit None
! .. Local Scalars ..
Complex (Kind=nag_wp) :: h, rho, s, s1, s2, s3, sigma
Real (Kind=nag_wp) :: nev_nrm
Integer :: ifail, ifail1, info, irevcm, j, &
lcomm, ldv, n, nconv, ncv, nev, &
niter, nshift, nx
! .. Local Arrays ..
Complex (Kind=nag_wp), Allocatable :: ax(:), comm(:), d(:,:), dd(:), &
dl(:), du(:), du2(:), mx(:), &
resid(:), v(:,:), x(:)
Integer :: icomm(licomm)
Integer, Allocatable :: ipiv(:)
! .. Intrinsic Procedures ..
Intrinsic :: cmplx
! .. Executable Statements ..
Write (nout,*) 'F12ASF Example Program Results'
Write (nout,*)
! Skip heading in data file
Read (nin,*)
Read (nin,*) nx, nev, ncv
n = nx*nx
lcomm = 3*n + 3*ncv*ncv + 5*ncv + 60
ldv = n
Allocate (ax(n),comm(lcomm),d(ncv,2),dd(n),dl(n),du(n),du2(n),mx(n), &
resid(n),v(ldv,ncv),x(n),ipiv(n))
ifail = 0
Call f12anf(n,nev,ncv,icomm,licomm,comm,lcomm,ifail)
! Set the mode.
ifail = 0
Call f12arf('SHIFTED INVERSE',icomm,comm,ifail)
! Set problem type.
Call f12arf('GENERALIZED',icomm,comm,ifail)
sigma = (5000.0_nag_wp,0.0_nag_wp)
rho = (10.0_nag_wp,0.0_nag_wp)
h = one/cmplx(n+1,kind=nag_wp)
s = rho/two
s1 = -one/h - s - sigma*h/six
s2 = two/h - four*sigma*h/six
s3 = -one/h + s - sigma*h/six
dl(1:n-1) = s1
dd(1:n-1) = s2
du(1:n-1) = s3
dd(n) = s2
! The NAG name equivalent of zgttrf is f07crf
Call zgttrf(n,dl,dd,du,du2,ipiv,info)
If (info/=0) Then
Write (nerr,99999) info
Go To 100
End If
irevcm = 0
ifail = -1
revcm: Do
Call f12apf(irevcm,resid,v,ldv,x,mx,nshift,comm,icomm,ifail)
If (irevcm==5) Then
Exit revcm
Else If (irevcm==-1) Then
! Perform x <--- OP*x = inv[A-SIGMA*M]*M*x
Call mv(nx,x,ax)
x(1:n) = ax(1:n)
! The NAG name equivalent of zgttrs is f07csf
Call zgttrs('N',n,1,dl,dd,du,du2,ipiv,x,n,info)
If (info/=0) Then
Write (nerr,99998) info
Exit revcm
End If
Else If (irevcm==1) Then
! Perform x <--- OP*x = inv[A-SIGMA*M]*M*x,
! MX stored in COMM from location IPNTR(3)
! The NAG name equivalent of zgttrs is f07csf
Call zgttrs('N',n,1,dl,dd,du,du2,ipiv,mx,n,info)
x(1:n) = mx(1:n)
If (info/=0) Then
Write (nerr,99998) info
Exit revcm
End If
Else If (irevcm==2) Then
! Perform y <--- M*x
Call mv(nx,x,ax)
x(1:n) = ax(1:n)
Else If (irevcm==4 .And. imon/=0) Then
! Output monitoring information
Call f12asf(niter,nconv,d,d(1,2),icomm,comm)
! The NAG name equivalent of dznrm2 is f06jjf
nev_nrm = dznrm2(nev,d(1,2),1)
Write (6,99997) niter, nconv, nev_nrm
End If
End Do revcm
If (ifail==0 .And. info==0) Then
! Post-Process using F12AQF to compute eigenvalues/vectors.
ifail1 = 0
Call f12aqf(nconv,d,v,ldv,sigma,resid,v,ldv,comm,icomm,ifail1)
Write (nout,99996) nconv, sigma
Write (nout,99995)(j,d(j,1),j=1,nconv)
End If
100 Continue
99999 Format (1X,'** Error status returned by ZGTTRF, INFO =',I12)
99998 Format (1X,'** Error status returned by ZGTTRS, INFO =',I12)
99997 Format (1X,'Iteration',1X,I3,', No. converged =',1X,I3,', norm o', &
'f estimates =',E12.4)
99996 Format (1X,/,' The ',I4,' generalized Ritz values closest to (',F8.3, &
',',F8.3,') are:',/)
99995 Format (1X,I8,5X,'( ',F10.4,' , ',F10.4,' )')
End Program f12asfe