Originally posted by: story_

Hi,

I was wondering if there is a way to write only specified variables (where some are discrete and some are not) to a .sol file using writeMIPStarts in Java API.

Thanks.

Hi

The level of detail to write to the file is controlled by setting the IloCplex.IntParam.WriteLevel parameter.

Values of this enumeration specify how much detail CPLEX includes when it writes MIP starts and solutions to a formatted file.

Auto = CPX_WRITELEVEL_AUTO   
AllVars = CPX_WRITELEVEL_ALLVARS   
DiscreteVars = CPX_WRITELEVEL_DISCRETEVARS   
NonzeroVars = CPX_WRITELEVEL_NONZEROVARS   
NonZeroDiscreteVars = CPX_WRITELEVEL_NONZERODISCRETEVARS

regards

So the answer to the question is "no".

However, it is easy to just write a .sol file yourself and include only the desired variables. A specification of the solution file format can be found in cplex/include/ilcplex/solution.xsd.

Originally posted by: story_

Hi,

Thank you for your response. 

I am wanting to write a subset of all variables, where only some of them are discrete. For instance, if we have the integer variables a,b,c, and d,e as continuous variables, I would like the .sol file to have a,b (discrete) and d (continuous).

The only method I could think of so far is to write all variables (using the write level 1), and remove other unwanted variables manually. But this probably will cause the .sol file to become very large (as I have over 50k variables) and I am not sure if it would be the most efficient way.

Like I said, the easiest is to just explicitly write the .sol file from your code instead of using a CPLEX function that creates the file for you. Using an existing (small) .sol file it should be simple to write such a file from your program.