Transport types for the remote object: process

Documents the process transport protocol supporting the remote object.

If the transport argument to CPXXopenCPLEXremote is processtransport, then CPLEX explicitly creates a new process which in turn instantiates the CPLEX Callable Library. CPLEX communicates with the newly created process using (named) pipes.

{"-stdio"|"-namedpipes=%s"}  [remote shell arguments] cplex "-worker=process" ["-logfile=%s"] ["-libpath=%s"]*

The process transport protocol understands the following arguments:

• -stdio

  Uses the stdin and stdout channels of the newly created process for input and output of messages. This situation implies that the newly created process must not use these two channels for its own purposes.

• -namedpipes=%s

  Uses named pipes created in the specified directory (in contrast to stdio).

• -worker=%s

  Specifies the transport type to be used by the worker process. For CPLEX applications, this argument must always be present, and its value must be set to process.

• -logfile=%s

  Specifies a file to which the process writes log messages. This argument is optional.

• -libpath=%s

  Adds a directory to the list of directories searched when dynamic libraries are loaded. This argument is optional. This argument can be repeated.

Other arguments are passed without change, exactly as they are, as command-line arguments to the new process that is started by the transport layer. These remaining arguments define the command line of the cplex process to be started. The following examples illustrate that point.

Example 1: Start a process on the local machine using named pipes in the current directory.

            char const *args[] = { "-namedpipes=.", "cplex", "-worker=process" };
            int status;
            CPXENVptr env;
            env = CPXXopenCPLEXremote("processtransport", sizeof(args) / sizeof(args[0]),
                                      args, &status);
          

Example 2: Start a process on the remote machine (remote.com for example) using named pipes of that process for communication.

          char const *args[] = { "-namedpipes=.",
                                 "/usr/bin/ssh", "remote.com", "cplex",
                                 "-worker=process" };
          int status;
          CPXENVptr env;
          env = CPXXopenCPLEXremote("processtransport", sizeof(args) / sizeof(args[0]),
                                    args, &status);
          

Both those examples assume that the cplex binary file is installed and accessible according to the environment variable $PATH. If such is not the case, then you need to specify a full path to the cplex binary file.

In Example 2, the cplex binary file must be installed on the remote machine (identified in the example as remote.com); and the binary file must be accessible in the remote $PATH environment variable there.

Example 2 also assumes that a remote login, not requiring a password, has already been set up and is available to the application.