| GENERAL INFORMATION: |
| |
| This code is an improvement over the original Water code in SPLASH, |
| but is mostly the same. The best source of descriptive information, |
| therefore is the original SPLASH report. The main change is that |
| the locking strategy around the updates to the water accelerations |
| (in interf.C) is improved: a process updates a local copy of the |
| relevant particle accelerations, and then accumulates into the shared |
| copy once at the end. |
| |
| RUNNING THE PROGRAM: |
| |
| To see how to run the program, please see the comment at the top |
| of the water.C file or run it as "WATER-NSQUARED -h". The input file |
| has 10 parameters, of which the ones you would normally change |
| are the number of molecules and the number of processors. The other |
| parameters should be left at their values in the supplied input file |
| in the normal case. Please do not set the CUTOFF value (the last |
| parameter) to a nonzero number in the normal case. |
| |
| The only compile-time option (ifdef) is one that says to change the |
| input distribution. The default input distribution of molecules |
| arranges them on a cubical lattice. For this, the number of molecules |
| must be an integer cube (8, 27, 64, 343, 512 ...). If one wants |
| to use a non-cube number of molecules, one can ignore the lattice |
| and use a random distribution of particles in a cubical space |
| by invoking the -DRANDOM compile-time option (see file initia.C). |
| Note that a random distribution does not make too much physical sense, |
| since it does not preserve chemical intermolecular distance ranges. |
| If you do not use the lattice but use -DRANDOM, please say so explicitly |
| in any results you report. |
| |
| The program reads random numbers, to compute initial velocities, from |
| a file called random.in in the current working directory. It does |
| this rather than generate random numbers to facilitate repeatability |
| and comparability of experiments. The supplied file random.in |
| has enough numbers for about 512 molecules. If you need more, add |
| more random numbers between -4.0 and +4.0 to the file. |
| |
| BASE PROBLEM SIZE: |
| |
| The base problem size for an upto-64 processor machine is 512 molecules. |
| For this number of molecules, you can use the input file provided (and |
| change only the number of processors). |
| |
| DATA DISTRIBUTION: |
| |
| Our "POSSIBLE ENHANCEMENT" comments in the source code tell where one |
| might want to distribute data and how. Data distribution, however, |
| does not make much difference to performance on the Stanford DASH |
| multiprocessor. |
