integer constraints in lp format do not seem to be respected
| Affects | Status | Importance | Assigned to | Milestone | |
|---|---|---|---|---|---|
| lp-solve (Ubuntu) |
New
|
Undecided
|
Unassigned | ||
Bug Description
Inequality constraints and integer variables give clearly incorrect results, which are not explicitly mentioned in the documentation.
For instance, trying to solve the following program in lp format:
min: x;
x > 0;
int x;
Results in:
Value of objective function: 0
Actual values of the variables:
x 0
Which is clearly incorrect.
The solution, which involves using some artificial boundaries such as "x > 0.00000001" instead of "x > 0", is NOT intuitive and nowhere mentioned in the documentation. This is extremely frustrating for novice users.
If there are limitations which prevent lp_solve from correctly parsing the given input program without having to add some residual value to "0", then at least it should be mentioned in the documentation.
| Martin Pokorny (martin-truffulatree) wrote | #1 |
This is actually described in the lp_solve documentation under the description of the LP file format, where it states:
<constraint> is an optional constraint name followed by a colon plus
a linear combination of variables and constants or (just one)
constraint name followed by a colon (a range) or (just one) variable
name without a colon (a bound), followed by a relational operator,
followed again by a linear combination of variables and constants,
ending with a semicolon. The relational operator can be any of the
following: "<" "<=" "=" ">" ">=". There is no semantic difference
between "<" and "<=" nor between ">" and ">=" (even for integer
variables!).