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