[Bug-glpk] A bug has been detected in glpk 3.0.8

[Andrew Makhorin]

A bug has been detected in glpk 3.0.8 due to a report provided by
Dr Hans Mittelmann.

If you run glpsol (or your program, which calls glp_simplex or
lpx_simplex) under GNU Linux, and the message "optimal solution
found" immediately follows the message "*** stop-watch overflow ***",
most probably the solver erroneously terminated the search as if there
were a limitation on the solution time, i.e. in this case the final
solution reported by the solver is not optimal.

The message "*** stop-watch overflow ***" means that a value returned
by the clock function (which is a standard C function) is less than the
value returned on the last call to this function. Since in GNU Linux the
clock function is ultra fast (CLOCKS_PER_SEC = 1000000), this message
appears every 72 minutes. Therefore if the solution process takes more
than one hour, the mentioned bug will happen.

In order to fix up the bug just replace the function watch() in the
file 'glplib3.c' by the following line:

double watch(void) { return 0.0; }