Early Experiences with the Cray T3E at the SDSC |
Part I: Background
Type of code ported:
MOVIE
The Coalescence of Two Neutron Stars.
(326K)
Parallel Platforms on which our code has been executed previously:
- Thinking Machines CM-5;
- IBM SP-2.
Table 1 documents the performance of our
code on these machines. As the timings in the table illustrate,
we have been unable to achieve a high degree of scalability on the SP-2
platform.
As we explain in more detail in an accompanying discussion,
the CFD code we currently are using on the T3E was ported from the
CMFortran version of our code.
Table 1
|
Timings on Several Different Machinesa |
Compiler |
nodes |
Total time (sec) |
Seconds per timestep |
Y/MP Ratio |
MP-1 Ratio |
Cray Y/MP |
f77 |
1 |
2660.0 |
13.30 |
1.00 |
0.36 |
MasPar MP-1 |
mpf |
8,192 |
947.4 |
4.74 |
2.81 |
1.00 |
Cray C90 |
Fortran90 |
1 |
802.8 |
4.01 |
3.31 |
1.18 |
MasPar MP-2 |
mpf |
8,192 |
388.6 |
1.94 |
6.84 |
2.44 |
" |
" |
4,096 |
681.4 |
3.41 |
3.90 |
1.39 |
|
CM-5 |
cmf Block3D |
32 |
1098.3 |
5.49 |
2.42 |
0.86 |
" |
" |
64 |
584.6 |
2.92 |
4.56 |
1.62 |
" |
" |
128 |
319.3 |
1.60 |
8.33 |
2.97 |
" |
" |
256 |
187.0 |
0.93 |
14.23 |
5.07 |
|
SP2 |
XLHPF Block3D |
16 |
982.4 |
4.91 |
2.71 |
0.96 |
" |
" |
64 |
471.4 |
2.36 |
5.64 |
2.01 |
" |
" |
128 |
374.6 |
1.87 |
7.10 |
2.53 |
FOOTNOTE:
aTo obtain these execution times,
the CFD code was run for 200 integration timesteps utilizing a grid
resolution in cylindrical coordinates of
128 × 64 × 64.
It should be noted that the timing comparisons
were obtained with a purely hydrodynamic version of the code, that is, a
solution to the Poisson equation and, hence, the self-gravity of the fluid was
not included. Only minor changes in the mpf code were required before it could be compiled and successfully run on the C90 and the CM-5.
However, because a Fortran90 compiler was not available on the Y/MP,
we utilized VAST to first convert the mpf code to f77 before the code
was compiled and run on the Y/MP.