| Malthe Eisum |
May 4, 2016 15:41 |
what is Execution(/CPU) time when running parallel jobs?
I'm doing DNS simulations of a turbulent wave boundary layer, using a slightly modified version of pimpleFOAM (a body force is added to drive the flow).
To estimate the optimal number of processors I want to do a small study of the execution time with increasing no. of processors.
I have therefore two questions:
1) The listed execution time is the accumulative time eg. from code example:
Code:
ExecutionTime = 1.31 s
at the second time step indicates that from the start of time loop to the end of the second time step there have elapsed 1.31 s CPU time. Also meaning that from time step one to two CPU time elapsed.
2) Is the listed execution time an estimate for one processor or a sum of all eg. (for 8 processors) the sum of CPU time is eather or since CPU time is close to clock time I would consider that the first case is more likely. But I would like to be confirmed.
Code:
Starting time loop
Courant Number mean: 0 max: 0 velocity magnitude: 0
deltaT = 0.00107403
Time = 0.00107403
dU0dt = dU0dt [0 1 -2 0 0 0 0] (3.51258e-06 0 0)
DILUPBiCG: Solving for Ux, Initial residual = 1, Final residual = 0.0074636, No Iterations 1
DILUPBiCG: Solving for Uy, Initial residual = 0, Final residual = 0, No Iterations 0
GAMG: Solving for p, Initial residual = 3.27377e-09, Final residual = 3.27377e-09, No Iterations 0
time step continuity errors : sum local = 1.65251e-28, global = 3.78285e-29, cumulative = 3.78285e-29
GAMG: Solving for p, Initial residual = 3.15544e-09, Final residual = 3.15544e-09, No Iterations 0
time step continuity errors : sum local = 1.59278e-28, global = 4.38014e-29, cumulative = 8.16298e-29
dU0dt = dU0dt [0 1 -2 0 0 0 0] (3.51258e-06 0 0)
DILUPBiCG: Solving for Ux, Initial residual = 0.086718, Final residual = 1.17036e-10, No Iterations 2
DILUPBiCG: Solving for Uy, Initial residual = 7.4425e-11, Final residual = 7.4425e-11, No Iterations 0
GAMG: Solving for p, Initial residual = 3.48381e-09, Final residual = 3.48381e-09, No Iterations 0
time step continuity errors : sum local = 1.75853e-28, global = 4.38014e-29, cumulative = 1.25431e-28
GAMG: Solving for p, Initial residual = 3.59952e-09, Final residual = 3.59952e-09, No Iterations 0
time step continuity errors : sum local = 1.81694e-28, global = 5.37562e-29, cumulative = 1.79187e-28
ExecutionTime = 1.24 s ClockTime = 1 s
Courant Number mean: 2.75088e-29 max: 8.27559e-12 velocity magnitude: 4.59998e-10
deltaT = 0.0012803
Time = 0.00235434
dU0dt = dU0dt [0 1 -2 0 0 0 0] (3.52066e-06 0 0)
DILUPBiCG: Solving for Ux, Initial residual = 0.999568, Final residual = 0.00876511, No Iterations 1
DILUPBiCG: Solving for Uy, Initial residual = 9.62229e-11, Final residual = 9.62229e-11, No Iterations 0
GAMG: Solving for p, Initial residual = 2.84384e-08, Final residual = 2.84384e-08, No Iterations 0
time step continuity errors : sum local = 1.71118e-27, global = 1.55691e-27, cumulative = 1.7361e-27
GAMG: Solving for p, Initial residual = 3.60149e-08, Final residual = 3.60149e-08, No Iterations 0
time step continuity errors : sum local = 2.16706e-27, global = 1.8607e-27, cumulative = 3.5968e-27
dU0dt = dU0dt [0 1 -2 0 0 0 0] (3.52066e-06 0 0)
DILUPBiCG: Solving for Ux, Initial residual = 0.0487339, Final residual = 1.07318e-10, No Iterations 2
DILUPBiCG: Solving for Uy, Initial residual = 1.39588e-10, Final residual = 1.39588e-10, No Iterations 0
GAMG: Solving for p, Initial residual = 3.72728e-08, Final residual = 3.72728e-08, No Iterations 0
time step continuity errors : sum local = 2.24275e-27, global = 1.8607e-27, cumulative = 5.4575e-27
GAMG: Solving for p, Initial residual = 3.09594e-08, Final residual = 3.09594e-08, No Iterations 0
time step continuity errors : sum local = 1.86287e-27, global = 1.70881e-27, cumulative = 7.16631e-27
ExecutionTime = 1.31 s ClockTime = 1 s
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