# Setting Concurrency with `concurrency`

If you are running the tests on a multi-processor computer, you can use concurrency to speed your test runs. Use the `concurrency` command to specify the number of tests to run concurrently:

> jtharness ... [initial-set-up commands] ... `-concurrency` number ... [task-command] ...

See About the Command-Line Examples for a description of the use of > jtharness in the example.

Unless your test suite restricts concurrency, the maximum number of threads specified by the `concurrency` command is 256. See your test suite documentation for additional information about using concurrency values greater than 1.

When creating a command string to specify the number of tests to run concurrently, include the commands in the following sequence:

1. Set up a configuration
2. Specify the concurrency value (`concurrency` number)
3. Include the `runtests` command (optional).

See Command-Line Overview for a description of the command line structure.

## Detailed Example of `concurrency` Command

In the following example, myconfig`.jti` represents a file name that might exist on your system and value represents a numeric value from 1 to 256 that you might use.

Command Options Format Example:

> jtharness `-config` myconfig`.jti -concurrency` value `-runtests`

See Formatting a Command for descriptions and examples of other command formats.

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