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Total wall clock time

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Old   September 16, 2019, 20:48
Default Total wall clock time
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Siddharth
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Hi,

I was wondering what 'total wall clock time' means in Fluent? I assumed it to be the physical (actual) time taken to run a simulation. I have been running a transient simulation on 4 cores for about 10 hours. I used the time usage option to find the wall clock time and below is the output.

Quote:
Performance Timer for 159259 iterations on 4 compute nodes
Average wall-clock time per iteration: 0.017 sec
Global reductions per iteration: 43 ops
Global reductions time per iteration: 0.000 sec (0.0%)
Message count per iteration: 2107 messages
Data transfer per iteration: 0.291 MB
LE solves per iteration: 1 solves
LE wall-clock time per iteration: 0.008 sec (45.3%)
LE global solves per iteration: 1 solves
LE global wall-clock time per iteration: 0.000 sec (0.3%)
LE global matrix maximum size: 10
AMG cycles per iteration: 1.000 cycles
Relaxation sweeps per iteration: 198 sweeps
Relaxation exchanges per iteration: 0 exchanges
Time-step updates per iteration: 1.00 updates
Time-step wall-clock time per iteration: 0.002 sec (9.3%)

Total wall-clock time: 2709.066 sec
The total wall clock time does not match with the actual time. 2709 sec is approximately 45 mins which is well below the 10 hrs of wall clock time.
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Old   September 16, 2019, 21:36
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Lucky Tran
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Does 159259 iterations make sense?


Indeed it has a meaning similar to actual real-world time but it concerns only solver time. If there is a discrepancy, then you have overhead such has disk I/O.
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