Mule incompatibility with Numpy version 2.3

[Martin Yeo (trexfeathers)]

https://numpy.org/doc/stable/release/2.3.0-notes.html#deprecations

NumPy 2.3 has finally removed the deprecated ndarray.tostring() method. There are several uses of this in Mule, e.g. mule.ff._WriteFFOperatorUnpacked.to_bytes(). It looks like the fix is super-simple: just change the calls to use .tobytes() instead (tostring was apparently a misnomer).

This has hit Iris now due to uses of Mule during performance benchmarking. We can work around it with a monkey-patch. However it will become relevant to everyone else next time the Scientific Software Stack is updated, since that will bring in Numpy 2.3.

I would be happy to submit a fix for this, but I'm completely out of touch ¹! Are Mule changes still happening on FCM, or has Mule been migrated to Git? Let me know and I'll do by best to fix ².

Footnotes

1. my ONLY use of FCM so far was another fix for Mule back in 2021! ↩

2. assuming I can remember how 🤞 ↩

[Yaswant Pradhan (yaswant)]

Thanks Martin Yeo (@trexfeathers) sounds good to me. Can we have a chat about this offline please.

Cc: @MetOffice/ssdteam