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Advice on Compiler Options

 
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BILLDOWS



Joined: 22 Jul 2005
Posts: 83
Location: Swansea, UK

PostPosted: Wed May 24, 2006 9:16 am    Post subject: Advice on Compiler Options Reply with quote

Any advice on the following issue would be much appreciated:

I have a large FTN77 / Clearwin program which works fine when compiled using /zeroise together with /fullcheck or /check or /save or /debug but yields erroneous results when run with just /zeroise.

I use implicit none throughout. There are quite a mixture of Int*2 and *4 variables and arrays in the program.

I have also used my FTN95 licence to compile it (not run) and the only errors are when I call API functions. I could cut these out and try to run using checkmate and any other recommended options?

Any suggestions / explanations of behaviour would be appreciated.



Thanks, Bill Dowsland
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PaulLaidler
Site Admin


Joined: 21 Feb 2005
Posts: 4919
Location: Salford, UK

PostPosted: Wed May 24, 2006 12:30 pm    Post subject: Advice on Compiler Options Reply with quote

Bill

The options that stand out are /save and /zeroise. The others are less likely to make a difference.

I would switch off /zeroise and use /undef (and /full_undef if it is available) and initialise all variables before their use.

/save should also be avoided unless you know what it does and are sure you need it.

Assuming /undef identifies the problem, you can then switch it off for production purposes.
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BILLDOWS



Joined: 22 Jul 2005
Posts: 83
Location: Swansea, UK

PostPosted: Tue May 30, 2006 11:51 pm    Post subject: Advice on Compiler Options Reply with quote

Many thanks Paul - it was indeed an array local to a sub which was not being completely zeroised.

COULD I JUST EXTEND THE QUESTION A LITTLE - The historic code I am working on has a lot of largish arrays (several each 5000*10) which are I*2, done (from the in-code comments) to cut storage requirements in the DBOS era, mixed up with lots of I*4 - messy, and something I would like to standardise [subject to any specific I*2 needs] to I*4.

Would I be correct in thinking that under Win32, given the virtual address space, code and data can use up to 2Gb, thus such memory considerations largely vanish?

Thanks, Bill
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PaulLaidler
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Joined: 21 Feb 2005
Posts: 4919
Location: Salford, UK

PostPosted: Wed May 31, 2006 12:24 am    Post subject: Advice on Compiler Options Reply with quote

Bill

Yes the address space extends to 2GB. As you increase your memory requirements there may be a speed penalty as pages start to be swapped from RAM to disc.
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