[WIP] Tag / debug tape recordings

[oleburghardt]

Proposed Changes

Add feature to record a tape for debug purposes (as a tool for AD / discrete adjoint / .. developers), using CoDiPack's codi::RealReverseTag.

Related Work

Supposed to help finding remaining errors in #2317.

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[oleburghardt]

This will be resolved inside CoDiPack :)

[pcarruscag]

Looks good, can you document how it would be used?

[oleburghardt]

Looks good, can you document how it would be used?

Sure. Added an option so that you can compile the AD build using the tag type (-Dcodi-tape=Tag) for now. You will have to check out the current develop branch of CoDiPack.
I'm thinking about writing a "SetRecording_Debug" next. Together with config file options and so on... documentation will follow.

[oleburghardt]

Would you be okay with replacing 32 by a function to find the next power of 2? (Requirement of alignas.) Or could this be done any better?

[pcarruscag]

For what type is the result not a power of 2?
If we use a fixed number instead of sizeof, arrays of this type may take more space than necessary.

[oleburghardt]

The reverse tag type is 24 I think. If sizeof(Scalar) is already a power of 2 that function should of course not change it :)

[pcarruscag]

I see, so the tag doesn't have a float/double part? Then it should be ok to round Size * sizeof(Scalar) to the next power of 2.
Or maybe using Size * alignof(Scalar), that may be more generic and achieve the desired result.

[oleburghardt]

Well it does contain at least a double for the primal value (show must go on). I'll check or ask what the remaining bytes are for besides two ints for index and tag. But sizeof(RealReverseTag) = 24.