CTEST_PARALLEL_LEVEL

This is a CMake Environment Variable. Its initial value is taken from the calling process environment.

Specify the number of tests for CTest to run in parallel. For example, if CTEST_PARALLEL_LEVEL is set to 8, CTest will run up to 8 tests concurrently as if ctest(1) were invoked with the --parallel 8 option.

Changed in version 3.29: The value may be empty, or 0, to let CTest use a default level of parallelism, or unbounded parallelism, respectively, as documented by the ctest --parallel option.

CTest will interpret a whitespace-only string as empty.

In CMake 3.28 and earlier, an empty or 0 value was equivalent to 1.

This environment variable is ignored if ctest --parallel is given on the command line, and is overridden by the jobs field of a test preset, if that field is set.

A test preset may also set this variable itself, using its own environment field. Doing so is equivalent to setting the variable in the calling process's environment, except that it takes effect only for the preset's Test step, and only if execution.jobs is not also set (which would take precedence, as noted above).

When a test preset is used by a ctest_test() command in a Dashboard Client via CTest Script, that command's own PARALLEL_LEVEL argument, if given, takes precedence over the preset's execution.jobs field. Together, PARALLEL_LEVEL and execution.jobs take precedence not only over this environment variable, but over an explicit ctest --parallel on the command line as well. This differs from a preset used directly via ctest --preset, where an explicit --parallel always wins over the preset's execution.jobs field.

See ctest(1) for more information on parallel test execution.