[Coin-discuss] Cbc 2.2 reports integer-infeasible

[Andrew Makhorin]

>> In your mps file some integer columns are not listed in the BOUNDS
>> section. Glpk sets default lower and upper bounds of such columns to 0
>> and +inf, resp. However, the IBM OSL documentation says:
>> 
>>         "For non-integer variables, the default bounds on columns are
>>         0 and +inf. For integer variables, the default bounds on columns
>>         are 0 and 1."
>> 
>> AFAIK, Cbc uses the latter convention that explains why the results
>> are different.

> This makes a lot of sense, thanks for the clarification.  The MPS file
> was produced by GLPK 4.27 using

>     glpsol --cpxlp test.lp --wmps test.mps --check

> If this bound-ambiguity does not exist in the Cplex LP format, would it
> make sense to make the bounds explicit in the MPS file in GLPK MPS writer?

Probably there must be an option to specify how to process such columns.
On the other hand, to avoid the ambiguity it is sufficient to make all
integer columns bounded, because if glpsol did not place some columns in
the bounds section, they had lower and upper bound 0 and +inf, resp., in
the original file 'test.lp'.