Materialize adjoint in mul with HermOrSym

[dkarrasch]

Fixes #850, at least the original issue. Promoting Bool to some BlasFloat seems to be very tricky in terms method ambiguities.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 91.90%. Comparing base (c9ad828) to head (d71f9b8).

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1191   +/-   ##
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  Coverage   91.89%   91.90%           
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  Files          34       34           
  Lines       15360    15366    +6     
=======================================
+ Hits        14115    14122    +7     
+ Misses       1245     1244    -1     

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[dkarrasch]

x-ref JuliaLang/julia#52787 for the Bool case.

[araujoms]

Why not implement @mcabbott 's suggestion, though? It is faster for small matrices and avoids a copy.

[dkarrasch]

We seem to avoid wrapping results in adjoint or transpose, or, better said, we materialize the final wrapper:

A' * Q = copy((Q' * A)')

We return wrapped results only when the first factor is an adjoint vector.

[araujoms]

Why, though? I don't see the problem with wrapping results in adjoint or transpose.

[dkarrasch]

@andreasnoack Do you remember why we typically materialize products that we compute by the adjoint formula, except for AdjOrTransAbsVec?

[andreasnoack]

I don't remember the specifics here. Only that the wrapped versions can sometimes lead to performance issues because they wrappers sometimes causes dispatch to slow fallback definitions for AbstractMatrix.