What is the default solver if I don’t specify one?

The listing of default solver for each problem type is below:

Problem Default Solver
LP CPLEX
MIP CPLEX
RMIP CPLEX
NLP IPOPTH
MCP PATH
MPEC NLPEC
CNS PATH
DNLP IPOPTH
RMINLP IPOPTH
MINLP SHOT
QCP IPOPTH
MIQCP SHOT
RMIQCP IPOPTH
EMP CONVERT

The full list of default solvers that comes with GAMSPy can be listed with:

gamspy list solvers

The current default solvers list is: CONOPT, CONVERT, CPLEX, IPOPT, IPOPTH, KESTREL, NLPEC, PATH, and SHOT. But be aware that this list might be subject to change in the future.