Fortran Matrix Help

[AdYrL]

Hi,this is a program i have for solving a 3x3 matrix. The thing is, that it won't solve. I suspect that there's somthing wrong with my definition, it'll appear as 0 errors but like 7 warnings. Can anybody help me with this?

program testing

double precision A(3,3),B(3),Z(1000)
real N,lud
! Initialising the Matrix A

A(1,1)=1
A(1,2)=2
A(1,3)=3

A(2,1)=4
A(2,2)=2
A(2,3)=2

A(3,1)=1
A(3,2)=3
A(3,3)=5

!Initialising the matrix B
B(1)=2
B(2)=3
B(3)=2

call SOLVER(A,B,N,lud,Z)

print*,"The values are:",Z(1),Z(2),Z(3)

end program testing

!*************************************************
subroutine SOLVER(A,B,N,lud,Z)

real lda,N,ipvt(1000),info,lud,IDAMAX,j,k,kp1,l,nm1,kb

double precision A(1000,1000),B(1000),Z(1000),t,AMD(1000,1000)

common /ludcmp/ipvt,AMD

nm1=N-1

do 5 i=1,N
Z(i)=B(i)
5 continue

if (lud.eq.0) goto 99

do 6 i=1,N
do 6 j=1,N
AMD(i,j)=A(i,j)
6 continue

!This part for decomposing A is taken from DGEFA.

info=0

if (nm1.lt.1) go to 70
do 60 k=1,nm1
kp1=k+1
l=IDAMAX(N-k+1,AMD(k,k),1)+k-1
ipvt(k)=l
if (AMD(l,k).eq.0.0d0) goto 40
if (l.eq.k) goto 10
t=AMD(l,k)
AMD(l,k)=AMD(k,k)
AMD(k,k)=t
10 continue
t=-1.0d0/AMD(k,k)
call DSCAL(N-k,t,AMD(k+1,k),1)
do 30 j=kp1,N
t=AMD(l,j)
if (l.eq.k) go to 20
AMD(l,j)=AMD(k,j)
AMD(k,j)=t
20 continue
call DAXPY(N-k,t,AMD(k+1,k),1,AMD(k+1,j),1)
30 continue
go to 50
40 continue
info=k
50 continue
60 continue
70 continue
ipvt(N)=N
if (AMD(N,N).eq.0.0d0) info=N
if (info.ne.0) pause 'Division by zero in SOLVER!'

99 continue

!This part for finding solution of AX=B is taken from DGESL.

if (nm1.lt.1) goto 130
do 120 k=1,nm1
l=ipvt(k)
t=Z(l)
if (l.eq.k) goto 110
Z(l)=Z(k)
Z(k)=t

....
....
...
....

Thanks!

 

[mikrom]

Before you use any subroutine you should know what it should do.
Here you should solve the system of 3 equations
A*Z = B.
If A is 3x3 matrix, then Z should have 3 elements too. So deklare first

double precision A(3,3),B(3),Z(3)

Then calling the SOLVER subroutine has this form

call SOLVER(A,B,N,lud,Z)

So, before the above call you have to set these arguments too:
N - I guess it's number of equations, i.e. 3 in your case
lud - I guess it's flag for LU-decomposition of the matrix. If you don't want to do LU-decomposition, then lud=0 (see your source)

Try this

...
N=3
lud=0
call SOLVER(A,B,N,lud,Z)
...

and your program will probably work

 

[AdYrL]

Hi,thanks for your help but i've tried out what you have suggested, but the same problem has still occured. It still showed 0 errors and 5 warnings when compiling. Adding the n=3 and lud =0 before the calling of my solver program resulted in a windows error box. Do u know what's the problem still? Thanks!

 

[mikrom]

If you want to help, you should post the 5 warnings exactly.

 

[AdYrL]

The warning message actually says:

Warning: In the call to IDAMAX, actual argument #1 does not match the type and kind of the corresponding dummy argument.
l=IDAMAX(N-k+1,AMD(k,k),1)+k-1

Warning: In the call to DSCAL, actual argument #1 does not match the type and kind of the corresponding dummy argument.
call DSCAL(N-k,t,AMD(k+1,k),1)

Warning: In the call to DAXPY, actual argument #1 does not match the type and kind of the corresponding dummy argument.
call DAXPY(N-k,t,AMD(k+1,k),1,AMD(k+1,j),1)

somthing to do with N-k

Thanks

 

[mikrom]

The problem is, that you have in your program N declared as REAL and the routines IDAMAX, DSCAL, DAXPY expect as 1st argument Integer -see e.g:

http://www.netlib.org/slatec/lin/idamax.f

http://www.netlib.org/slatec/lin/dscal.f

http://www.netlib.org/slatec/lin/daxpy.f

Try to declare your N as integerin your program testing and in the subroutine solver:

integer N

lud could be integer too.