[CPMD-list] MEMORY ALLOCATION

[Salomon Billeter]

Hi,

this problem has more than one solution, depending on your system
architecture. Although 4GB is the maximum amount of memory 32bit (unsigned)
pointers can address, the space addressable within one segment is often
limited to 2GB, the maximum of a signed 32bit pointer. These are possible
solutions:

1) You tell the linker to limit the data segment to more than 2GB if your
system supports this with 32bit pointers. The manpage of your 'ld' program
should tell you how.
2) You compile CPMD for 64bit pointers if your system supports this. This
will slow down your program somewhat.
3) You compile CPMD to run parallel using MPI and let two processes run on
the same node. If you have one processor, this will slow down your program,
but if you have more than one processor in your machine, it could even
result in faster execution because much more parts of CPMD will run in
parallel compared to the SMP parallelism.

Best regards,
Salomon
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