Shriram, Total memory usage _per_processor_, scales as: memory/proc ~ [ C * lelt * lx1*ly1*lz1 + c * lelg ] * (8 bytes/word) where C is a moving target, but is somewhere between 200 and 400, and c ~ 2. (The code is a bit fat right now and needs a good clean-up, which is slated for next fall.) Also, C can be influenced by some parameters in the SIZEu file, namely, mxprev, lgmres, ldimt. If your problem has nelt=120,000 elements and you're running on 1000 processors, you should set lelt=120 and lelg=120000. This would give you the smallest possible memory footprint for that case. Note that some machines, such as BG/L or BG/P have very little memory per MPI process (e.g., 256 MB on BG/L and 512 MB on BG/P, of which only about 80% is available for the simulation). Does this help? Paul On Tue, 2 Feb 2010, [email protected] wrote:

Hi,

When I am trying to run a big simulation (Nele > 120,000) , on certain clusters / supercomputers, Nek5000 crashes even though the physical memory used is very less. For example, on certain machines, with Nele = 120,000, we couldn't go more than lx1 of 7 while on different architecture we could go up to lx1 = 12. Is this issue concerned with compilers or the architecture of the machine ?

Thanks Shriram Jagannathan Texas A&M University