using more than 700Mb of RAM

[matthewhort]

I have a code than can use more than 1 Gb of RAM. However once the memory needed gets above about 700 Mb I get a memory fault.

I have come across this before and have solved in the past under INtel compiler 7.1 on RedHat 8 using teh -static command. Though I can no longer find out why this worked. I am now trying under RedHat 9 and yes I know that this is not supported. -static now couses an error. As I can no longer figure out why I was using -static anyway I have decided to post in the hope that someone can help, if not in solving the issue then atleast with my level of knowledge.

Matt

[TimP]

If your assertion is correct, you should not be close to any fixed limit. I run programs which use more than 2GB on RH8, which use several methods of allocating memory. Have you tried compiling with runtime error checking enabled (-C -g) with and without optimization? That wouldn't tell you anything about Cray pointer allocated memory, but it should tell you about various bounds transgressions.

[matthewhort]

The error (memory fault) occurs at the end of the compile and results in no exectable being created.

I was able to duplicate the error under REDHAT 8 if I did not compile with -static.

[Martyn_C_Intel]

The default Linux kernel on IA-32 loads shared libraries at 1 GB, which limits the contiguous address space available to your program. You will get a load time error if your program + static data exceed this. This could be what you are encountering under Red Hat 8.

The possible workarounds are:
1) build with -static, ie don't load any shared libraries.
2) allocate some of your data differently, on the heap or on the stack, which will put it at a higher address than the shared libraries.
3) rebuild your Linux kernel so that the shared libraries get loaded at a different default address
4) use the prelink command to place the shared libraries that you need at a different (higher) address.

I do not know how any of this relates to RH9. But you could still try dynamic allocation (eg ALLOCATE in F90), or putting array data on the stack with -auto (remember to increase the maximun stacksize with ulimit -s 1000000).

Martyn