The first line contains the solution label (the parameter Slab is set via the PDEXE command); the second line contains the headers of the data columns - the iteration number, cycle number, loop number, and the random variable names. The iteration number and cycle number tell the PDS to which group (with specific PDS method and settings) the loops belong. Subsequent lines provide specific iteration, cycle, loop, and input sample values for the defined input variables.

The PDS also creates a file where the results are stored. The name of the results file is jobname_Slab.pdrs. Before the job is executed, the file looks like this:

In the first line, the PDS enters the solution label. In the second line are the headers for the data columns: the first four columns are the iteration, cycle number, loop number, and an error flag. The fifth and subsequent columns are for the random input variable and random output parameter values. If you

run a subsequent analysis (same type of analysis with the same solution label), the cycle is incremented, the loop count is reset to 1, and the result file is appended.

For example, the content of the result file could look like this:

Note

Loops ending with an error are deemed "not trustworthy", i.e. if the loop lead to an error, then the calculated results are probably wrong. Those loops will have the error flag in the fourth column set to "1" instead of "0". Those loops will be excluded from the probabilistic postprocessing altogether, i.e. the loops will not be used for the response surface fitting and also the statistical analysis in connection with a Monte Carlo simulation will skip those loops.

1.3.9.2. Serial Analysis Runs

Serial execution of the probabilistic analysis is useful for smaller models, or if you have access to only one machine.

Command(s): PDEXE

GUI: Main Menu> Prob Design> Run> Exec Serial> Run Serial

1.3.9.3. PDS Parallel Analysis Runs

To save time when analyzing large models with PDS, use the parallel processing option available under the PDEXE command, if you have multiple CPUs available.

To successfully execute a probabilistic analysis in parallel mode you need to follow three steps:

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1.Configure the remote machines that you want to use for parallel processing. See Machine Configurations (p. 29) for details. You must have account privileges on all remote hosts.

2.Configure the local machine that you want to use for managing the parallel processing. See Configuring the Master Machine (p. 33) for details.

3.Start the parallel execution.

Each of these steps is explained in detail in the following sections.

An understanding of the following terms will be useful in the discussion of the parallel analysis.

•Simulation: A simulation is a set of input variables used with the analysis file to produce the output variables

•Parent Process: The parent process is the executable which manages the creation of input parameters, communication with child processes, and postprocessing of output parameters (i.e. this is where the session runs, which you started to perform a probabilistic design analysis). There is only one parent process for a parallel analysis.

•Child Process: A child process is a server running on a particular slave machine which processes a

simulation. There can be any number of children for a given parent process.

•Master Machine: This is the machine on which you are running the parent process. If this machine has more than one CPU you may want to also use it as a slave machine.

•Slave Machine: This is the name of the machine on which you are running the child process. If the slave machine has more than one CPUyou may want to run more than one child process.

•ANSYS Nanny: This is a program in the parent process that starts a child process on a slave machine; manages the transfer of files and data between the parent process and child processes and eventually terminates the child processes on the various slave machines and removes temporary files.

•ANSYS Thin Server: This is an application, which must be running on the slave machine, which is responsible for tranferring files between the master machine and slave machine as well as starting a session for each child process. This application may be started automatically (remote shell option) or you can start it manually (connection port option).

•ANSYS Server: This is the application using TCP/IP which receives commands and return information to the parent process (client-server).

•Connection Port: This is the port on which the ANSYS Thin Server accepts connections from a Master Machine.

•Communication Port: This is a port on which the ANSYS Thin Server will allow communications from a Master Machine.

Caution

For security reasons, ANSYS, Inc. recommends that you use parallel processing within your local network protected by a firewall. There is minimal security when using the ANSYS Thin Server. The client that connects to the server has all of the permissions allowed by the person or account starting the ANSYS Thin Server.