How to display the "particle.state" in Parcels 3.0.0 output

[Cyuan-hub]

Hello, @erikvansebille.
I am currently using Parcels version 3.0.0. However, I noticed that the output does not display the value of particle.state. I would like to know how I can view the value of particle.state. Is there a specific method or setting that allows the value of particle.state to be visible in the output results?
Any suggestions or advice you provide would be greatly appreciated.

[erikvansebille]

By default, particle.state is not in the zarr-output because its write-status is set to False. Have you tried changing the write_status of particle.state? E.g. using pset.set_variable_write_status('state', True)

[Cyuan-hub]

I modified the state = Variable('state', dtype=np.int32, initial=StatusCode.Evaluate, to_write=True) in particle.py in Parcels, and I was able to get the value of particle.state in the zarr output. I haven't tried using pset.set_variable_write_status('state', True), but I will give it a try.

In addition,

1. I need to observe the changes in the value of particle.state. In the output, I can only see the changes from StatusCode.Evaluate to StatusCode.delete, but I never see StatusCode.ErrorOutOfBounds. Why is this happening?
2. Using print in this code causes the program to crash. How can I modify it to avoid this issue?
   Here's the code for reference:

def CheckOutOfBounds(particle, fieldset, time):
    print(OutBound.astype(str))
    print(state.astype(str))
    OutBound = particle.state
    if particle.state == StatusCode.ErrorOutOfBounds:
        particle.delete()

[erikvansebille]

Hi @Cyuan-hub, below answers to your two questions

1. I need to observe the changes in the value of particle.state. In the output, I can only see the changes from StatusCode.Evaluate to StatusCode.delete, but I never see StatusCode.ErrorOutOfBounds. Why is this happening?

That is because these error codes are 'captured' by the kernel at the end of the loop, and then processed. The loop can only complete with a StatusCode.Evaluate or StatusCode.delete, so you won't indeed see other StatusCodes in the output. A workaround would be to define your own Variable and set that to the value of particle.state. Something like

MyParticle = JITParticle.add_variable(Variable('printstate'))

def PrintState(particle, fieldset, time):
    particle.printstate = particle.state

pset.execute([<YOUR OTHER KERNELS HERE>, PrintState], ...)

2. Using print in this code causes the program to crash. How can I modify it to avoid this issue?

The print function is (in JIT-mode) pretty limited in what it can do, because we have to hand-convert the print-statement from python to C++ see this part of the code if you're interested. See the Kernels section of the parcels overview tutorial for some examples of what kind of print-statements can be used in JIT-mode.
Alternative, if you do want to use more complicated printing (especially for debugging), is to switch to Scipy-mode, by replacing JITParticle to ScipyParticle in your code.

[Cyuan-hub]

Hi, @erikvansebille, thanks for your helpful response and guidance. Sorry for the delay in getting back to you; things have been pretty hectic lately. I'll keep you updated on any progress or if I run into any issues. Thaks a lot.