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Getting around 160 MB limit in g77 under cygwin


Jim McDonald wrote:

I read your message about this g77 limit in the cygwin mail archives.

I just installed cygwin-1.5.13-1 today and ran into the 160-MByte
limit on memory for static variables under g77.  I used

g77 -mno-cygwin maxarray.f -o maxarray

to compile

     program maxarray
     real*8 a(240000000)
     do i=1,240000000
        a(i) = i
     end do
     print *, a(240000000)
     stop
     end

The resulting executable ran to completion.  Without -mno-cygwin,
the executable returned immediately, with no output or error
message.  Using -Wl,--stack,8388608 did not help, and actually
reduced the memory limit.  Setting the registry entry
heap_chunk_in_mb to 1024 did not help either, and with that entry
still in effect, my array storage has exceeded that limit.
I'm running cygwin under Windows 2000 SP4 + latest hotfixes.

If this solution works for you, you may want to post it at
cygwin.com or on comp.lang.fortran.

- Jim McDonald
 Naval Research Lab, Code 6841
 (202) 404-6936, fax 767-1280
 James.A.McDonald at nrl.dot navy mil


This works now.  I can again get 770 Mb of useful array
space with 512 Mb of RAM using Windows XP Pro, as I could a couple of
years ago by increasing the stack size.

I did try -mno-cygwin before, but without success. Your message prompted me to try again, and now it works. Either I blundered the first time, or there has been some change in my system since then: 1) I reinstalled the old cygwin version for which changing the stack size was at one time, but no longer, an effective fix 2) I cleared the Windows Prefetch directory.

Some comments in the cygwin mail archives suggest that the problem resides in the "cygwin loader" (a modification of gnu ld?). I suppose using -mno-cygwin avoids invoking the cygwin loader, but I am a bit disturbed that the problem did not disappear when I first tried that option. Has anyone else had problems with large fortran arrays when using -mno-cygwin?






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