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direct4 - simple N-body integrator for GRAPE-4 Pipelined N-body engine
direct4 in=in_file out=out_file [parameter=value]
direct4
is a simple equal timestep direct N-body integrator that is used with the
GRAPE-4 Pipelined N-body engine by compiling it with the grape I/O libraries.
With a special compile flag this program can also compute the forces on
the front-end instead of the GRAPE4 board.
The following parameters
are recognized in any order if the keyword is also given:
- in=
- input file
name, in standard snapshot(5NEMO)
format. No default.
- out=
- output file name,
in snapshot(5NEMO)
format. No default.
- dt=
- integration timestep. [Default:
1/32]
- tstop=
- Stoptime [Default: 2.0]
- dtout=
- Output timestep of datadumps.
[Default: 0.25]
- dtlog=
- Output timestep for the logfile. [Default: 0.25]
- eps=
- Standard softening length. All particles share the same gravitational softening
length. [Default: 0.05]
- pcmode=t|f
- Add a Predictor-Corrector step to the leapfrog
integrator. [Default: f]
The original program source code (grape.c)
could be compiled with many flags (-Dxxx) to target different hardware boards
(GRAPE1, GRAPE2, GRAPE3, HARP3). Although this was a flexible solution to
code maintenance, the current source code (direct4.c) is a severely trimmed
version of the original for HARP3=1 and NOSHARE.
Here are the compilation
options: (not some will be mutually exclusive of others):
EXACT_CALCULATION no GRAPE, use exact calculations on HOST
CHECK_GRAPE compare GRAPE with exact HOST calculations
hackcode1(1NEMO)
, nbody0(1NEMO)
, snapshot(5NEMO)
, atos(1NEMO)
,
stoa(1NEMO)
usr/pjt/grape direct4.c
[makino] grape.c (original code, compilable for all boards)
Jun Makino, Peter Teuben
16-sep-89 V1.0 Initial workbench version w/ exact force calculation JM
17-May-97 V2.0 Simplified version for NEMO and GRAPE4 PJT
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