ILOG CPLEX 11.0 User's Manual > Advanced Programming Techniques > Parallel Optimizers > Using Parallel Optimizers in the Interactive Optimizer

Using Parallel Optimizers in the Interactive Optimizer

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In the Interactive Optimizer, ILOG CPLEX invokes parallel optimization by default whenever a deterministic algorithm is available. For mixed integer programming (MIP), this policy means the following sequence of commands invokes parallel deterministic MIP optimization:

  1. Start the parallel CPLEX Interactive Optimizer with the command cplex at the operating system prompt.
  2. Enter your problem object and populate it with data as usual.
  3. Call the parallel optimizer with the mipopt command.The optimizer will use the maximum number of available threads in deterministic mode.

In order to invoke parallel optimization of continuous models in the Interactive Optimizer, you must abandon determinism. You can do so explicitly with the parallel mode parameter, or you can do so implicitly with the threads parameter.

To abandon determinism explicitly by means of the parallel mode parameter, do this:

  1. Start the parallel CPLEX Interactive Optimizer with the command cplex at the operating system prompt.
  2. Enter your problem object and populate it with data as usual.
  3. Enter the command: set parallel -1. The optimizer will use the maximum number of available threads in opportunistic mode.
  4. Optimize.

To abandon determinism implicitly by means of the thread parameter, do this:

  1. Start the parallel CPLEX Interactive Optimizer with the command cplex at the operating system prompt.
  2. Enter your problem object and populate it with data as usual.
  3. Enter the command: set threads n where n is a number strictly greater than 1 (one). The optimizer will use the specified number of threads in opportunistic mode.
  4. Optimize.
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