Outline of Program Run

The actual PROGRAM block is in ~/bearclaw/lib/driver.f90. This block is essentially a process-timing wrapper for the actual main function of the program, the BEAR subroutine (defined in ~/bearclaw/lib/bearez.f90). The PROGRAM block logs the start time, runs the program, and reports the difference in system timestamps as the process time.

The BEAR subroutine can be divided into several operational phases:

1. Load program data from bear.data and bear.rundata files.

2. Depending on whether or not the Restart flag is set:

a) If Restart is true, then load the tree data from the specified frame

(i.e., load a previously-run simulation starting at a specific frame).

b) If Restart is false, then begin setting up a new problem (meaning that

you are about to start running a brand-new simulation).

3. Run the calculations.

4. Release system resources and exit subroutine.

Steps 1, 2, and 4 are predominantly governed by code from the ~/bearclaw/lib directory, most notably the bearez.f90, beario.f90, treeops.f90, and mpi_exec.f90 files. Step 3 uses more code from the ~/bearclaw/contrib/astro directory, which pertains to the actual problems being solved.