forums.silverfrost.com

[liuzhe1213]

I have the subroutine
SUBROUTINE linmul_sky_vc(cv,disps,svc,kdiag)
!
! This subroutine forms the product of symmetric matrix stored as
! a skyline and a vector.
!
IMPLICIT NONE
INTEGER,PARAMETER::iwp=SELECTED_REAL_KIND(15)
REAL(iwp),INTENT(IN)::cv(,disps(0
REAL(iwp),INTENT(OUT)::svc(0
INTEGER,INTENT(IN)::kdiag(
INTEGER::n,i,j,low,lup,k
REAL(iwp):,zero=0.0_iwp
n=UBOUND(disps,1)
DO i=1,n
x=zero
lup=kdiag(i)
IF(i==1)low=lup
IF(i/=1)low=kdiag(i-1)+1
DO j=low,lup
x=x+cv(j)*disps(i+j-lup)
END DO
svc(i)=x
IF(i==1)CYCLE
lup=lup-1
DO j=low,lup
k=i+j-lup-1
svc(k)=svc(k)+cv(j)*disps(i)
END DO
END DO

WRITE(11,'(2(A,I5))')(" vc matrix")
WRITE(11,'(6E12.4)')svc

RETURN
END SUBROUTINE linmul_sky_vc

but when I call this subroutine, there are some error information, the error is the following:
Run-time Error
*** Error 112, Reference to undefined variable, array element or function result (/UNDEF)

but I define the variables, arrary in the main programme and subroutine. someone can help me to explain how to call the subroutine, the dummy argument and real argument, thanks a lot

[DrTip]

Hi there

I think your probelm is that you are using automatic arrays in the subroutine arguments

to get this to work you will either need to define the size if the arrays in the subroutine ie expicityly state the size of the arrays

or use a an interface in the calling program

simple example would be

subroutine sub1(cv)
real cv(:)


write (*,*) cv
cv = cv + 1.0
end subroutine

program test

interface
subroutine sub1(cv)
real cv(:)
end subroutine
end interface

real cv(4)

cv = 6.9

call sub1(cv)



write (*,*) cv

end program

writing interfaces is a bit tedious if you are doing it every time you call a subroutine I would suggest that you put the interface in a module and then have a use use the module but this is just my preference.


Carl

ps when submitting code I suggest you disable smilies

[JohnCampbell]

I am familiar with the skyline equation solver and I would recommend the first place you look is to check the contents of the index array KDIAG.
Why not first create a simplified routine which lists out the index value for each equation and the value of the diagonal for this equation, to check you have correctly constructed the skyline index.

This is an old fortran style routine, so defining arrays as :-
real*8 disps(*)
integer*4 kdiag(*)

I'm sure the original version had "n" as a subroutine argument. Shouldn't it be the size of svc. ubound(disps) does not look correct.

[PaulLaidler]

The quick way to find out exactly what is undefined is to step through the code using the integrated debugger. In fact all you need to do is to run the code using the debugger and it will stop at the point of failure and the variables window will show you what is undefined.