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This fix enables usage of the Eigen SparseQR starting in Eigen-3.3. It optimizes the code enabling it
to work with the new assignation interface of Eigen-3.3, which is more strict than that of Eigen-3.2.
It provides the same optimization for DenseQR code, and omits the extraction of the Q matrix in DenseQR
as this is not used anywhere else.
[NOTE: This is only to be merged after Debian has updated the Eigen-3.3-alpha1 package]
See:
http://forum.freecadweb.org/viewtopic.php?f=10&t=12769&start=30#p104740https://forum.kde.org/viewtopic.php?f=74&t=129115
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