Creating Grid from dynamically allocated data - has to be persistent?

[Ben Buckner]

Hi - I'm having some trouble managing a large set of interpolations, and I'm starting to suspect that ceres' Grid* objects created from a pointer to data only hold a shallow copy, so that if the original data gets deallocated, it crashes. Is this the case, so that the original pointer has to be kept valid as long as the Grid* and derived interpolators are alive?

Thanks,

Ben

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[Sameer Agarwal]

Ben,

The grid objects does not make copies of the data, you can see that here

https://github.com/ceres-solver/ceres-solver/blob/master/include/ceres/cubic_interpolation.h#L385

from the grid2d constructor.  So yes, the arrays containing the data need to be live for the lifetime of the Grid object.

Sameer

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[Sameer Agarwal]

This should of course be better documented, but I assumed that the header is small enough that it will be evident to the reader. I will update the header to make this more explicit.

[Ben Buckner]

Thanks Sameer - I was thinking that the interpolator would precalculate some of the interpolation, but from the code, it looks like it's a very thin wrapper, so that there's no reason to store interpolator objects, which is what I was trying to do. I'll just pass data pointers to the cost functions and instantiate the interpolator when it initializes the cost function structure.

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[Sameer Agarwal]

Yes, the interpolator has no precomputed state, just some sanity checks. 

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