Throwing an error when dt has too high precision #1558
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VascoSch92
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May 8, 2024
parcels/particleset.py
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| if dt > 0 and dt <= 1e-6: | ||
| if abs(dt) <= 1e-6: | ||
| raise ValueError('Time step dt is too small') | ||
| if dt*1e6 % 1 != 0: |
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What do you want to check here?
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As I say in the comment of the PR, we've seen that Parcels unexpectedly fails (outputfiles miss some timeslices) when dt has a precision finer than 1e-6.
So dt=3.001 works, but dt=3.0000001 doesn't.
I want to catch these latter cases
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Do you have a proposal for a cleaner code to do the same?
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ah ok sorry. Now is clear. Perhaps just add parenthisis: (dt * 1e6) % 1 to make it more clear. Otherwise is perfect :-)
As not supported anymore since parcels v3.0 Also cleaning up code as suggested by @VascoSch92
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As found by @sruehs and @ezekiel-lemur, parcels output can 'skip' timesteps when
dthas a very high precision (i.e. many digits behind the comma). This is very likely because of the test done when considering which particles to writehttps://github.com/OceanParcels/parcels/blob/a0ea4044c3ced351b65ec3a19ea3bd8d29f8bd3d/parcels/particledata.py#L322-L328
Solution is to throw an error when users provide a
dtthat has higher precision than 1e-6. Note that parcels before already threw an error whendt < 1e-6, now a value likedt=1+1e-6would also be caughtThe new testcase in example_globcurrent (with
dt = 81.2584344538292) indeed shows how the output file misses a few time-snapshots if this error is not raised