Hi Peter,
> I wrote a litte C++ demo which shows that the error occurs in v4.31 (and
> previous versions), but not in v4.33. The same happens with the
> executables (glpsol.exe).
> Maybe this information is useful for you.
> But anyway, since the latest version behaves nicely, everything is OK!
I tested your demo model with glpk 4.31. In fact, the results were
incorrect.
In the changelog I found the following record concerning glpk 4.32:
* glpmpl01.c
A bug was fixed. Due to this bug iterated expressions having
an indexing expression whose dummy indices are bound to some
values, i.e. like sum{(i+1,j,k-1) in E} x[i,j,k] are evaluated
incorrectly. Namely, current value of such expressions is not
invalidated when corresponding dummy indices (like i and k in
the example above) are changed, that erroneously results in the
same value evaluated for the first time.
Most probably this bug (which now is fixed) caused incorrect results.
BTW, I noticed that in your code you are using routines
_glp_lpx_read_model and _glp_lpx_write_mps; this is not a good idea,
because these symbols may disappear in further versions of the package.
Please use documented api routines glp_mpl_... and glp_write_mps
instead.
Best regards,
Andrew Makhorin
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