README - The solver "cplex" uses CPLEX (a...

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The solver "cplex" uses CPLEX (a trademark of ILOG) to solve integer, mixed-integer, linear programming, and quadratic problems, including (with version 9) problems with quadratic constraints possibly involving integer variables. Normally cplex is invoked by AMPL's solve command, which gives the invocation s cplex stub -AMPL in which is an AMPL generic output file (possibly written by "ampl -obstub" or "ampl -ogstub"). After solving the problem, cplex writes a stub.sol file for use by ampl's solve and solution commands. When you run ampl, this all happens automatically if you give the AMPL commands g option solver cplex; solve; You can control cplex by setting the environment variable cplex_options appropriately (either by using ampl's option command, or by using the shell's set and export commands before you invoke ampl). You can put one or more (white-space separated) phrases in $cplex_options. A few of the phrases are single words: o Phrase Meaning autoopt Use CPLEX's automatic choice of optimizer (dualopt). baropt Use the barrier algorithm (unless there are discrete variables). bestbound Return in suffix .bestbound the best known bound on the objective value. For MIP problems with a finite bestnode value (see below), bestbound = bestnode. bestnode For MIP problems, return the best node value in suffix .bestnode of the current objective and problem. For non-MIP problems, set .bestnode to Infinity for minimization, -Infinity for maximization. If CPLEX has not yet found a best node value for a MIP problem, or has completely solved the problem, it similarly supplies 1e75 or -1e75 as the best node value. concurrentopt When hardware and licensing permit, try several methods in parallel (with CPLEX versions >= 8). dual Solve the dual problem. dualopt Use a dual simplex algorithm. maximize Maximize the objective, regardless of model specification. minimize Minimize the objective, regardless of model specification. siftopt Solve ever larger sequences of subproblems until the whole LP is solved (versions of CPLEX >= 8). primal Solve the primal problem (default, via "dualratio" described below). Note that "primal", "dual", and
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"dualratio" determine what problem is presented to CPLEX, whereas "primalopt" or "dualopt" instructs CPLEX to use a primal or dual simplex algorithm, rather than making an automatic choice (which currently is always "dualopt"). Thus "primalopt" and "dualopt" are orthogonal to "primal", "dual", and "dualratio". The best settings depend on the problem. primalopt Use a primal simplex algorithm. relax Ignore integrality: treat integer variables as continuous. version Show the current version. Others are name-value pairs, possibly separated by '=', as in O iterations 600 or iterations=600 or iterations = 600 any of which limits cplex to 600 iterations. The following names may occur in name-value pairs. For convenience, the list also repeats the above single-word phrases, denoting them with "Single-word phrase". a Name Comment absmipgap
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README - The solver "cplex" uses CPLEX (a...

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