[gmx-users] Double precision bug

Andrew Horsfield horsfield at fecit.co.uk
Tue Dec 18 16:03:57 CET 2001


Does anyone know why the double precision version of mdrun can fail for 
conjugate gradient and steepest descent runs when I use PME, but not 
cut-off, with the error:

Fatal error: ci = -2147483648 should be in 0 .. 1099 [FILE nsgrid.c, LINE 214] 

The failure occurs at the first step. Using cut-off gives nonsense results
(the energy diverges to -infinity). The unit cell has a net charge of
-3,and contains 16118 atoms. Single precision does not seem to be adequate
to relax the cell.

I am using a PIII running Linux (RH7.1), and am using gcc to compile. I
have tried changing the compile options to reduce the level of
optimization, and used efence to trap any memory leaks, but without



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