support output for dt < 1

[trontrytel]

When running with dt < 1s we generate no output. This is because our output is decided based on:

if mod(sim.TS.t, sim.Stats.frequency) == 0

which runs into rounding errors when the arguments are not integers. Seems like the namelist key is labelled frequency, but we use it in the code more like output interval.

We could instead start using it like this (i.e. more like a frequency - "every how many steps we should do output)". This way we would avoid floating point issues:

if mod(iter, sim.Stats.frequency) == 0

If we want to keep the current output specification, some ugly workaround solution could look like this:

if (sim.TS.t - sim.Stats.frequency * div(sim.TS.t, sim.Stats.frequency, RoundNearest)) < eps(1.0) * sim.TS.t_max

Let me know what you think. If we go with the integer friendly way I'm not sure if I should change something more in the NetCDF io files.

[charleskawczynski]

This looks fine to me (assuming that the output frequency translates well for the plots). I suppose this will all disappear when we use OrdinaryDiffEq for timestepping since they have an API for callback frequency.

[ilopezgp]

I prefer having the output frequency as time units, not timestep units. If this is difficult using seconds, we can just use milliseconds internally.

[trontrytel]

Looks like we want to keep specifying output in seconds and not time steps. @charleskawczynski are you ok with the proposed alternative to mod?

[charleskawczynski]

Looks like we want to keep specifying output in seconds and not time steps. @charleskawczynski are you ok with the proposed alternative to mod?

I'm fine with that if it works

[trontrytel]

Ended up with this:

if mod(round(Int, sim.TS.t), round(Int, sim.Stats.frequency)) == 0

It does not change the behaviour for cases where dt is an int. And provides a reasonable output for cases there dt < 1

[trontrytel]

bors r+

[bors]

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