When you compile a large project, using the parallel build option can reduce the needed time by factors (typically, three to five times). The improvement depends on the number of cores and on the speed of your machine.
Parallel build means that the builder does not compile one file after each other, but instead runs a set of parallel builds. This is especially useful for host machines having multiple cores or CPU. Each CPU can do a compilation and balance the build load across all available CPU to cut the build time.
To speed up the build time, go to the project settings and click C/C++Build in the left pane. Go to the Behavior tab in the right pane:
The parallel build option is enabled by default. Select the number of “parallel jobs” depending on the number of CPU on your machine. Click Apply to save the changes and continue or Aplly and Close to save the changes and quit the Properties dialog.
The possible disadvantage of the parallel build is, the compilation errors from all jobs are reported in the same Problems view in parallel. If the project has many errors in many files, consider turning parallel build off during the error fixing.