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Documentation of FiveArg() #236
Description
If we set the trait FiveArg(), is it also necessary to implement the three argument mul!? Something like:
LinearMaps.MulStyle(A::MyMap) = FiveArg()
function LinearMaps._unsafe_mul!(y, A::MyMap, x::AbstractVector, α, β)
...
end
LinearMaps._unsafe_mul!(y, A::MyMap, x::AbstractVector) = LinearMaps._unsafe_mul!(y, A, x, 1, 0)
If so, it would be useful to note this in the "Custom Maps" section of the documentation.
If you don't need to do this then I have some other issue... :)
Activity
dkarrasch commentedon Oct 7, 2024
Sorry for my slow response. That's a good question, I haven't looked things in here for quite a while. It seems that within this package, even the
FiveArg()types have the three-arg_unsafe_mul!defined, but that may be "by tradition" or "by necessity". I think we introduced it to indicate whether or not one can do multiply-and-add in-place, without allocating the intermediate multiplication result. I never thought about it in terms of "saving" the three-arg method.If you don't, which issue comes up?
dkarrasch commentedon May 20, 2026
This is an old issue, but I hope that #248 addresses the issue.