Output desired size when AD container size is exceeded

[GiudGiud]

It would be convenient to tell users which size to resize to

This is coming up here
idaholab/moose#22191 (reply in thread)

[GiudGiud]

does metaphysicl allow verbose error messages?

[roystgnr]

We don't have a macro for it, but we ought to add one.

[roystgnr]

I'm not sure it's going to be possible to tell users which size to resize to. We hit that error and exit the first time we try to resize to anything larger than the current size, so we won't keep going to find out what the final required size is going to be. Add an ADReal with (dense, to simplify the example) gradient indices of [0,20) to a vector with indices of [15,35) and if your max sparse vector size is 30 the program is going to bail there and tell you needed 35, not wait around to find out that your code was later going to add a third vector with indices of [30,50) and a fourth with [45,65).

I almost said "can't" rather than "won't" keep going, because I'm wondering if there's anything we can do here to actually keep going until we're done.

Looking at DualReal.h, for one thing we really ought to have a DynamicSparseNumberArray option, not just SemiDynamicSparseNumberArray and NumberArray. "There is always some sparsity size which will make your program scream and die" is a design choice there for efficiency, not a MetaPhysicL-imposed requirement. And, that said... perhaps we could add a compile-time option to DSNA that updates a global maximum_sparsity_size with every resize? The additional potential performance issues (We'd need to do it atomically! Atomic max/min aren't in C++20; we'd need a loop!) make me cringe, but from a user interface perspective it would be nice to be able to say "recompile this way and run, then at the end of the program you'll see exactly how you'd need to recompile a different way to get your speedup back for this particular problem".

[lindsayad]

Especially given the recent timings in libMesh#29 I think it definitely makes sense to have DynamicSparseNumberArray be a configuration option for MOOSE. Perhaps it should even be the default depending on the application

[GiudGiud]

it could be part of our MOOSE makefile. When you include a module that needs a high number, we ask you to reconfigure?

[lindsayad]

Maybe but that is a pain for folks not using the AD portions of applications