Fix gradients and metric functions of distanceDir #724
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Types indicating differences or derivatives of unit vectors and unit quaternions are needed to handle values with the same dimensionality as the original types, but no constraints. The two enum also need to be handled explicitly in a switch statement to compile without warnings. However, it is better if the corresponding code raises an error, instead of computing something that has no consistent definition.
| { | ||
| return (x1.rvector_value - x2.rvector_value).norm2(); | ||
| return x1.dist2(x2); |
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So now the square of distance of two distanceDir is calculated as the angle between them. Should we clarify that in the documentation?
After merging this PR and #713 , I may still need to verify if polarPhi and distanceDir with a custom function could yield the same trajectories.
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So now the square of distance of two
distanceDiris calculated as the angle between them. Should we clarify that in the documentation?
Yes. I meant to do that, but forgot. I would say, though, that defining the distance as such is the same as taking the standard Euclidean distance (L^2 norm) but making it comply with the unit-vector constraint.
After merging this PR and #713 , I may still need to verify if
polarPhianddistanceDirwith a custom function could yield the same trajectories.
Yeah, that makes sense. (EDIT: the choice of metrics in colvarvalue should not matter there, only that the gradients of colvar::distance_dir are correct.)
Fixes #714