# Understanding a program is important; using a serial program version, follow codes line by line to improve to understand the program. (Parallel programming usually starts from a serial version.)# Use the simple data for the first time to understand keep track of data flow in a memory, and then increase data volume for the program.# When you missed the step you want to take a look in run-time debug mode, it will be better to start from the beginning in debug mode as data situation have already changed, and threads invocation also has been passed.