Solved

Fortran syntax help needed

Posted on 2002-06-29
8
491 Views
Last Modified: 2013-11-08
Trying to convert some Fortran to VB.  Here is a start of Fortran sub:

     SUBROUTINE TRIDAG(AAA,AAB,AAC,ABB,E1,NN,BCT,BCB)

     REAL*8 AAA(*),AAB(*),AAC(*),ABB(*),E1(20000)
     REAL*8 BET, GAM(20000)
     INTEGER BCT, BCB, NN
...

I thought argument AAA is an array, this also shows it is used as array:
     BET=AAB(I)-AAA(I)*GAM(I)

But, when sub is called, it seems only ONE ELEMENT is passed, instead of array:

      CALL TRIDAG(AA(1),AB(1),AC(1),BB(1),E1,NN,BCT,BCB)

     CALL TRIDAG(AA(2),AB(2),AC(2),BB(2),E1,NN,BCT,BCB)

Please, help me understand syntax ... maybe only subset of array AA is being passed?

Thanks
0
Comment
Question by:ameba
  • 5
  • 2
8 Comments
 
LVL 44

Accepted Solution

by:
bruintje earned 100 total points
ID: 7119200
Hi ameba,

sorry that i haven't any better idea then a download, there are two trials there, you showed only part of it but i guess there's more

http://www.winsite.com/bin/Search?id=2573

maybe it could help you going until the fortran people are lurking into this

HAGD:O)Bruintje
0
 
LVL 15

Author Comment

by:ameba
ID: 7119218
Thanks, Bruintje

I expect converter would convert it to:

Private Sub TRIDAG(AAA() As Double, AAB() As Double, AAC() As Double, ABB() As Double, _
     E1() As Double, NN As Long, BCT As Long, BCB As Long)

and the call to:
     CALL TRIDAG(AA(1), AB(1), AC(1), BB(1), E1, NN, BCT, BCB)

and I would get error "Expecting array" with "AA(1)" highlighted.
I'll try it later, if there isn't any 'easier' suggestion.
0
 
LVL 15

Author Comment

by:ameba
ID: 7119366
I tested "Convert Fortran to Visual Basic" but it doesn't recognize declaration.
Dim aaa(*)  as double   ' this doesn't work in VB

I don't see many Fortran programmers on EE  :-)
0
 
LVL 15

Author Comment

by:ameba
ID: 7119434
AAA(*)
is 'Assumed-size array', its size is known to caller
http://www.ibiblio.org/pub/languages/fortran/ch2-4.html

Call Tridag(AA(2), ...)
I think this means we are passing array block, starting with element 2.  Will try and see if I get the same results as with Fortran Exe.
0
Is Your Active Directory as Secure as You Think?

More than 75% of all records are compromised because of the loss or theft of a privileged credential. Experts have been exploring Active Directory infrastructure to identify key threats and establish best practices for keeping data safe. Attend this month’s webinar to learn more.

 
LVL 51

Expert Comment

by:ahoffmann
ID: 7119747
the fnction TRIDAG is called with an array for first 4 parameters, but the passed array is of size one elemnt.
That's ok (if the programmer wants this).
0
 
LVL 15

Author Comment

by:ameba
ID: 7119843
Thanks, ahoffmann

>the passed array is of size one elemnt.

I don't think it's possible that 2 means 'upper bound' in Call Tridag(AA(2), ...)
Because there is a loop on that array (2 to NN) and passed NN is 51 or 501.

C-------------------------------------------------------------------
C     SOLVER FROM "NUMERICAL RECIPES", TRIDAG
C-------------------------------------------------------------------

     SUBROUTINE TRIDAG(AAA,AAB,AAC,ABB,E1,NN,BCT,BCB)

     INTEGER NN
     REAL*8 AAA(*),AAB(*),AAC(*),ABB(*),E1(20000)
     REAL*8 BET, GAM(20000)
     INTEGER BCT, BCB, N

     DO I=1,20000
          GAM(I)=1.0
          E1(I)=1.0
     ENDDO

     N = NN
     
     IF(BCB.GT.1) N=N-1
     IF(BCT.GT.1) N=N-1
     
     BET=AAB(1)
     E1(1)=ABB(1)/BET

     DO I=2,N
          GAM(I) = AAC(I-1) / BET
          BET = AAB(I) - AAA(I) * GAM(I)
          E1(I) = (ABB(I) - AAA(I) * E1(I-1)) / BET
     ENDDO
     
     DO I=N-1,1,-1
          E1(I)=E1(I)-GAM(I+1)*E1(I+1)
     ENDDO

     RETURN
     END


I think I got it right, although program results are a bit different.  For argument "AA(2)" I'm passing part of array, i.e. first element is AA(2).

But I don't know for sure that program is correct.  Maybe what you are saying is true and all other elements AAA(2)to AAA(50) are zero's...?
I don't have Fortran compiler here to check.
0
 
LVL 15

Author Comment

by:ameba
ID: 7123361
Thanks.  Everything is working OK.  I have small difference when compared to Fortran results, but first 9 digits are the same. :-)

0.563085102878388 ' Fortran
0.563085102830859 ' VB
0.563085102830685 ' VB with option "Allow unrounded Floating Point Operations"
0
 
LVL 44

Expert Comment

by:bruintje
ID: 7123645
ameba thanks, but that wasn't necessary i only posted it as *help* don't know if it would help you did most of it yourself
0

Featured Post

Is Your Active Directory as Secure as You Think?

More than 75% of all records are compromised because of the loss or theft of a privileged credential. Experts have been exploring Active Directory infrastructure to identify key threats and establish best practices for keeping data safe. Attend this month’s webinar to learn more.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

A short article about a problem I had getting the GPS LocationListener working.
This is about my first experience with programming Arduino.
This theoretical tutorial explains exceptions, reasons for exceptions, different categories of exception and exception hierarchy.
The goal of the video will be to teach the user the difference and consequence of passing data by value vs passing data by reference in C++. An example of passing data by value as well as an example of passing data by reference will be be given. Bot…

930 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question

Need Help in Real-Time?

Connect with top rated Experts

14 Experts available now in Live!

Get 1:1 Help Now