I find the following bug in Fortran. Can some one advise why this occur?

What is the best strategy to avoid such possible errors. I appreciate for taking your time to answer me.

the simple code is:

!!!program explain.f

implicit none

double precision a,b

a=5.

b=25.

print*,"this is 'ok'!?",1./(a*b),(a*b)**-1.

print*,"why 'not ok' now?",1./(a*b)/(1.d10)**.2,

> ( a*b)**-1./(1.d10)**.2

stop

end !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

the following is how it is complied and run ~/ifort explain.f ~/./a.out this is 'ok'!? 8.000000000000000E-003 8.000000000000000E-003 why 'not ok' now? 7.999999451020953E-005 0.952863960639244

It is a common error for beginners. Do like this

a=5.d0 b=25.d0

"d0" makes real numbers double-precision. Take care

Hi

I am using Windows XP on a 32-bit system. I have recently installed "Compaq Visual Fortran 6.1", standard edition on my system. Is this compiler compatible with CFX?

I have tried to compile subroutine in tutorial 9 but I am getting following error:

ERROR CCL parser failed with message: Perl Syntax errors detected: Died at (eval 59) line 12.

How can I get rid of this error? Thanks in advance for your answer.

Regards

Sorry Jinwok,

That does not change the bug yet. Can you copy and paste in your pc and check it yourself.

Regards

Taw

this is not a bug. it calculates / and * from right to left and can save only 15 meaningful digit (for double precision number.) so digits more than 15 are dropped. if you change 1.d10 to 1.d5 you will see that there is no problem.

Hi Hadian, thanks for the response

I tried what you suggested, but I haven't still got as it should be for me, maybe double exponentiation may not be allowed. But even for these I write numbers like 10.d0, instead of 1.d10 or 1.d5, it didn't remove the bug!

Regards,

Tilek

change the line: print*,"why 'not ok' now?",1./(a*b)/(1.d10)**.2,(a*b)**-1./(1.d10)**.2 with: print*,"why 'not ok' now?",1./(a*b)/(1.d10)**.2,( a*b)**(-1.)/(1.d10)**.2

(just put -1 in parentheses.)

Hi Hadian,

Thank you very much. I have got it to working now. I will in the future give special care when writing routines like this.

Thanks,TAW

Am using the same compiler BUT I can not use files with:

USE file

i.e. I can not compile with the USE statement. I have to go back to the traditional fortran. Do you have any idea how to be able to use this statement and to let the compiler see it.

Thanks.

Hi Student

I have just installed compaq compiler. I am not even sure if this compiler is compatible with CFX. Are you using CFX? As I said I could not even compile a subroutine in tutorial 9. Any idea what could be wrong?

Thanks

I did not use it â€" try this one it may work.

http://g95.org/

have a nice journey!