I have been suddenly given a few very old fortran codes to compile and get working for my research group. Using ifort when I compile the code I get the following error:error #6526: A branch to a do-term-shared-stmt has occurred from outside the range of the corresponding inner-shared-do-construct.
Here is the bit of code that seems to be at fault:
...
IF(THRU.GT.0.D0) GO TO 120 00011900
L1=LL 00012000
A1=AA 00012100
DR1=DRR 00012200
RMAX1=RMAXX 00012300
RMIN1=RMINN 00012400
IF(DR1.EQ.0.D0) DR1=DRP 00012500
KMAX1=(RMAX1-RMIN1)/DR1+1.D-08 00012600
IF(KMAX1.GT.NN .OR. KMAX1.LE.0) KMAX1=NN 00012700
RINT1=RMAX1 00012800
IF(RMAX1.NE.0.D0) 00012900
2RMAX1=DR1*DFLOAT(KMAX1)+RMIN1 00013000
IUP=KMAX1 00013100
R=RMIN1 00013200
DO 120 K1=1,KMAX1 00013300
R=R+DR1 00013400
XX(K1)=R 00013500
120 CONTINUE 00013600
WRITE(IW,940) NAM1,IOPT1,L1,A1,DR1,RMAX1,RMIN1,ANU1,BNU1,CNU1 00013700
121 CONTINUE 00013800
...
Being quite unfamiliar with fortran I have been doing some searching and what I can see is that it does not like that IF statement branching to the terminal statement of the DO loop. Also, it seems that some older dialects or compilers supported this.
My questions is this: Is there an option that will allow ifort to successfully compile this? I.E. Is there a specific dialect compatibility option on ifort that will make this legal?
What are the side effects of that particular code on a compiler that would accept it? Is it possible that aside from the write statement the side effects are identical to going to line 121? Or was maybe the do loop supposed to go to 121?
I would consider modifying the code if not for the fact that my advisor told me that I should not make any changes whatsoever without consulting him first and so I ask this question to see if I need to consult him or not. That said if my only option is a modification to the code suggestions would be welcome for that so that I can have an idea of what needs to be done when I go to my advisor.
I'll note that the code in question isn't valid even as Fortran 77, but people did weird stuff back in the mists of time. I'll defer to any historian or person with experience. In particular, one should be very careful to understand any subtleties in the code in relation to my "answer" here.
If we assume that the intention of the goto given is to jump to code after the execution of the loop, then I answer about minimal change to the code.
Stripping line-number comments for clarity then
DO 120 K1=1,KMAX1
R=R+DR1
XX(K1)=R
120 CONTINUE
WRITE(IW,940) NAM1,IOPT1,L1,A1,DR1,RMAX1,RMIN1,ANU1,BNU1,CNU1
can be replaced by
DO K1=1,KMAX1
R=R+DR1
XX(K1)=R
END DO
120 WRITE(IW,940) NAM1,IOPT1,L1,A1,DR1,RMAX1,RMIN1,ANU1,BNU1,CNU1
I would be quite surpised if the author of the code intended the loop to continue to 121: no variable referenced by the write statement is updated in the loop. It is possible that the goto was intended to reference 121 but I do see that many variables are not updated in the section that would be skipped.