These diagrams represent timelines of the first few iterations of a loop in a routine for eight threads. (Threads are portions of a program that can be run independently of, and concurrently with, other portions of the program.) Dark blue shading indicates a running thread, light blue indicates an idle thread, and red represents inactive threads.

Case No. 1, top: In the original GCEM3D code, only one thread (the master thread) is active most of the time, while the remaining threads are idle. Case No. 2, bottom: In this case, the CAPO-parallelized version of the cloud modeling code, all threads are active most of the time (represented by the dark blue shading).