64-bit systems

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Especially on the x86_64 architecture, it is important to ensure you are linking to the correct libraries when installing code. Even when compiling in 64-bit mode, there remains an option of whether 32-bit or 64-bit integers are used (e.g., in the Lapack library).

The Gnu C compiler, gcc, reports the following default word sizes (in bytes): 

              P4    EM64T   
--------------------------
char           1      1
float          4      4
double         8      8
long double   12     16
short int      2      2
int            4      4
long int       4      8
long long int  8      8
*char          4      8

So it's quite interesting that even in 64-bit mode, not all types that might be 64-bit actually are (most notably the default int type is only 32 bits even on EM64T).

The blas/lapack libraries in /usr/lib64 on egate do not appear to work with PSI, perhaps because they use 8-byte integers whereas gcc uses 4-bytes by default.

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