The National Institute for Computational Sciences


Darter: Why shouldn’t I use "make -j 12" when compiling my code?

Unlike Darter's compute nodes, its login nodes have modest hardware specs: a single quad-core processor with 8 gigabytes of memory. However, each of the Darter login nodes may have up to 30 user login sessions active at any given time. As a result, a single user who runs a very processor- or memory-intensive task on a Darter login node can affect the work of several dozen other users. As a result, NICS recommends that concurrent makes ("make -j N") on Darter be done with an N of 2 or less.

Darter: I get the error message "OOM killer terminated this process". What is OOM?

This error message indicates that the node is running Out Of Memory. This could be the result of a bug in the code, or memory requirements for the given input. Note that due to optimistic memory allocation, you probably will not get a null pointer, even if you are out of memory. The program should be killed at the point the memory is used.

One quick solution might be to run with only four MPI processes per socket so each process gets a larger share of the memory on the node:

General: Why do I get the error: "/usr/include/c++/4.1.2/backward/backward_warning.h:32:2"?

#include is the Standard C++ way to include header files. The 'iostream' is an identifier that maps to the file iostream.h. In older C++ versions you had to specify the file name of the header file, hence #include . Older compilers may not recognize the modern method but newer compilers will accept both methods even though the old method is obsolete.

Darter: Why do I see the message: SEEK_SET is #defined but must not be for the C++ binding of MPI?

The following error message:

#error "SEEK_SET is #defined but must not be for the C++ binding of MPI" 

Is the result of a name conflict between stdio.h and the MPI C++ binding. Users should place the mpi include before the stdio.h and iostream includes.

Users may also see the following error messages as a result of including stdio or iostream before mpi:

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