LP on android devices

When I express a Linear Programming problem in a Pure Java environment, I get a solution A.

When I express thje same linear programming problem in a Java Android environment using the same problem modelling classes, I get a solution A', which doesn't match the constraints I express.

For instance, If I have a set of Xi variables, with each Xi >= 0, I can get some Xj < 0.

Or if I have Xi >= a, then in the solution, I can have Xi < a.

I noticed that for freechart library, they have made a special library for android (Jfreecharrtt for pure javan Afreechart for Android).

I have tried to compile the source with my android app, but the problem is the same.

Is it necessary to have a library built up for android devices ?

Is it possible to have commons-math for android ?

In advance thanks.

Regards.

Sylvain.