52 lines
2.4 KiB
Text
52 lines
2.4 KiB
Text
|
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.
|