Further methods on Fixed Rank and Stiefel

[kellertuer]

trafficstars

As a continuation of #49 the two papers

• [ ] https://arxiv.org/pdf/1209.0068.pdf
• [x] https://arxiv.org/abs/1604.05054 see this inverse redaction

provide further methods on the Stiefel and fixed rank manifold, though both work on a different metric than the current default.

[kellertuer]

The second paper is covered with #204.

[mateuszbaran]

The second paper is covered with #204.

That paper describes matrix logarithm on the Steiefel manifold, and currently that PR doesn't cover that?

[kellertuer]

Hm, does the second not cover fixed rank symmetric ones? Maybe I misread those? I don not mean the first paper, which definitely does Stiefel, yes.

[mateuszbaran]

The second one, 1604.05054, is about Stiefel and the first one, 1209.0068, is about fixed rank.

[kellertuer]

Sorry, then I confused them after opening them in tabs.