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Clarify which arg is modified in mul/div. #25421

Merged
merged 1 commit into from
Jan 19, 2018
Merged

Clarify which arg is modified in mul/div. #25421

merged 1 commit into from
Jan 19, 2018

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simonbyrne
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Another stab at JuliaLang/LinearAlgebra.jl#338. This is more or less the same as #24698 except updated for Transpose.

@JeffBezanson
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I suppose this solution is ok. The numbers aren't beautiful, but neither is needing to repeat an argument (especially if the argument isn't just a variable name).

@JeffBezanson JeffBezanson changed the title Clarify which are is modified in mul/div. Clarify which arg is modified in mul/div. Jan 5, 2018
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ldiv!(A, B) always overwrites B, and rdiv!(A, B) always overwrites A, so two-argument ldiv! and rdiv! do not share mul!'s relevant semantic ambiguity. Perhaps forgo attaching 2 to ldiv! and 1 to rdiv!? :)

@simonbyrne
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That's a good point. I renamed them for consistency, but would be happy to change them back.

@Sacha0
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Sacha0 commented Jan 6, 2018

I renamed them for consistency, but would be happy to change them back.

Might as well minimize the aesthetic suboptimality :).

@KristofferC
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KristofferC commented Jan 6, 2018

The convention is to modify the first argument. Therefore, for the function that adhere to the convention they can just be mul! and only those that break the convention needs a number.

Or is mul! an alias to mul!1 somewhere in this PR? Being forced to write mul!1 everywhere seems a bit unfortunate.

@tkelman
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tkelman commented Jan 6, 2018

There isn't an ambiguity in div, but ldiv does deviate from the argument order convention, and flagging that as such in the name seems beneficial to me. Could be done independently of changes to mul though.

@simonbyrne
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simonbyrne commented Jan 6, 2018

I'm not too fussed on the names, but as they're now unique it is simply a matter of sed to change them. If we want to rename the div ones as well, I have moved the changes their to the sb/div12 branch.

My main objection to mul1! being the 2-argument mul! is that mul2! is by far the more commonly used variant.

@deprecate A_mul_Bc!(A::AbstractMatrix,B::Diagonal) mul!(A, Adjoint(B))
function A_mul_B!(A::Diagonal,B::Diagonal)
depwarn("`A_mul_B!(A::Diagonal,B::Diagonal)` should be replaced with `mul1!(A, B)` or `mul2!(A, B)`.", :A_mul_B!)
throw(MethodError(A_mul_B!, Tuple{Diagonal,Diagonal}))
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MethodError(A_mul_B!, (A, B))?

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good catch.

@deprecate Ac_mul_B!(A::LQPackedQ{T}, B::StridedVecOrMat{T}) where {T<:BlasComplex} mul!(Adjoint(A), B)
@deprecate A_mul_B!(A::LQ{T}, B::StridedVecOrMat{T}) where {T<:BlasFloat} mul2!(A, B)
@deprecate A_mul_B!(A::LQ{T}, B::QR{T}) where {T<:BlasFloat} A*B
@deprecate A_mul_B!(A::QR{T}, B::LQ{T}) where {T<:BlasFloat} A*B
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Why transform from mul!(A, B) to A*B? :)

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Because they were implemented internally as copying already anyway

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Perhaps we should nix the corresponding mul! methods, being something of misnomers? (Perhaps you already have? :) )

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I did.

@deprecate Ac_ldiv_B!(A::Union{LowerTriangular,UnitLowerTriangular}, B::UpperTriangular) ldiv1!(Adjoint(A), B)
@deprecate Ac_ldiv_B!(A::Union{UpperTriangular,UnitUpperTriangular}, B::LowerTriangular) ldiv1!(Adjoint(A), B)
@deprecate At_ldiv_B!(A::Union{LowerTriangular,UnitLowerTriangular}, B::UpperTriangular) ldiv1!(Transpose(A), B)
@deprecate At_ldiv_B!(A::Union{UpperTriangular,UnitUpperTriangular}, B::LowerTriangular) ldiv1!(Transpose(A), B)
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ldiv!?

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good catch.

@@ -3115,7 +3119,7 @@ end
@deprecate At_mul_B!(C::AbstractVector , A::AbstractTriangular, B::AbstractVector) mul!(C, Transpose(A), B)
@deprecate At_mul_B!(C::AbstractMatrix , A::AbstractTriangular, B::AbstractVecOrMat) mul!(C, Transpose(A), B)
@deprecate At_mul_B!(C::AbstractVecOrMat, A::AbstractTriangular, B::AbstractVecOrMat) mul!(C, Transpose(A), B)
@deprecate A_mul_B!(A::Tridiagonal, B::AbstractTriangular) mul!(A, B)
@deprecate A_mul_B!(A::Tridiagonal, B::AbstractTriangular) mul2!(A, B)
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The odd method :).

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Agreed it is odd. We could get rid of it?

@deprecate A_mul_B!(A::$t{T,<:StridedMatrix}, B::StridedMatrix{T}) where {T<:BlasFloat} mul!(A, B)
@deprecate A_mul_B!(A::StridedMatrix{T}, B::$t{T,<:StridedMatrix}) where {T<:BlasFloat} mul!(A, B)
@deprecate A_mul_B!(A::$t{T,<:StridedMatrix}, B::StridedMatrix{T}) where {T<:BlasFloat} mul2!(A, B)
@deprecate A_mul_B!(A::StridedMatrix{T}, B::$t{T,<:StridedMatrix}) where {T<:BlasFloat} mul2!(A, B)
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mul1!?

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good catch.

@deprecate A_mul_B!(G::Givens, R::Rotation) mul2!(G, R)
@deprecate A_mul_Bc!(A::AbstractMatrix, G::Givens) mul1!(A, Adjoint(G))
@deprecate A_mul_B!(G::Givens, A::AbstractVecOrMat) mul2!(G, A)
@deprecate A_mul_B!(G1::Givens, G2::Givens) G1 * G2
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Why transform from mul!(G1, G2) to G1 * G2? :)

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The method just threw an error anyway.

@deprecate A_mul_B!(G1::Givens, G2::Givens) mul!(G1, G2)
@deprecate A_mul_Bc!(A::AbstractMatrix, R::Rotation) mul1!(A, Adjoint(R))
@deprecate A_mul_B!(R::Rotation, A::AbstractMatrix) mul2!(R, A)
@deprecate A_mul_B!(G::Givens, R::Rotation) mul2!(G, R)
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Another tricky one :).

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What's tricky about this?

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Without knowing the implementations of Rotation and Givens, from this signature one might not know whether this operation is possible and, if so, what it should do. (This signature certainly would have given me pause had I not recently looked at the relevant definitions :).)

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Yes, exactly.


@deprecate *(A::Factorization, B::Factorization) Matrix(A)*Matrix(B)
@deprecate *(A::Adjoint{<:Any,<:Factorization}, B::Factorization) adjoint(Matrix(A.parent)) * Matrix(B)
@deprecate *(A::Factorization, B::Adjoint{<:Any,<:Factorization}) Matrix(A) * adjoint(Matrix(B.parent))
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Are these deprecations related?

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Good question. I think I added them to deal with the QR/LQ business, but they may no longer be necessary.

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I think the story was that there were a couple of these methods, but they were inconsistently defined and mostly just did this anyway. It is probably better to define more specific deprecations though.

function (*)(Q::HessenbergQ{T}, X::StridedVecOrMat{S}) where {T,S}
TT = typeof(zero(T)*zero(S) + zero(T)*zero(S))
return mul!(Q, copy_oftype(X, TT))

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Why the additional empty line? :)

@@ -267,7 +278,7 @@ The reason for this is that factorization itself is both expensive and typically
and performance-critical situations requiring `rdiv!` usually also require fine-grained
control over the factorization of `B`.
"""
rdiv!(Y, A, B)
rdiv!(A, B)
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Does a three-argument rdiv! docstring still exist somewhere?

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There is no 3-arg rdiv!

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Now that's amusing 😄.

@@ -5,7 +5,7 @@ __precompile__(true)
module SuiteSparse

import Base: \
import Base.LinAlg: ldiv!, rdiv!
import Base.LinAlg: ldiv!, ldiv!
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ldiv!, ldiv!?

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A remnant from sed...

@@ -1,3 +1,4 @@

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? :)

@@ -385,6 +385,8 @@ function nnz(lu::UmfpackLU)
end

### Solve with Factorization
# TODO: these should probably be removed since they're not inplace
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👍

@@ -398,6 +400,7 @@ ldiv!(translu::Transpose{Float64,<:UmfpackLU{Float64}}, B::StridedVecOrMat{<:Com
ldiv!(adjlu::Adjoint{Float64,<:UmfpackLU{Float64}}, B::StridedVecOrMat{<:Complex}) =
(lu = adjlu.parent; ldiv!(B, Adjoint(lu), copy(B)))


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? :)

@test LinAlg.mul1!(copy(D1),D2) == D1*D2
@test LinAlg.mul2!(D1,copy(D2)) == D1*D2
@test LinAlg.mul1!(copy(D1),D2) == D1*D2
@test LinAlg.mul2!(D1,copy(D2)) == D1*D2
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Three repetitions of the same pair of tests?

@@ -493,6 +494,7 @@ end
let n = 5
A = rand(Float16, n, n)
B = rand(Float16, n-1, n-1)

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? :)

@Sacha0
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Sacha0 commented Jan 12, 2018

Modulo rebase this looks great! Much thanks for your persistence Simon! :)

Summary of sentiments: On the one hand, I sympathize with Andreas that the names mul!, ldiv!, and rdiv! are lovely. On the other hand, I am not as clever as Andreas, so two-argument mul! does trip me up now and again. So overall I favor merging the minimal set of renames necessary to sort the latter (i.e. two-argument mul! -> (mul1!|mul2!) as in this pull request) while leaving everything else as is.

In short, 👍 for these changes (or any spelling variation on mul1!/mul2!). Best!

@JeffBezanson
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I think this is ready to go now.

@JeffBezanson JeffBezanson force-pushed the sb/mul12 branch 2 times, most recently from d84c9cf to cd67a43 Compare January 18, 2018 22:22
@JeffBezanson JeffBezanson merged commit 6c3cee7 into master Jan 19, 2018
@JeffBezanson JeffBezanson deleted the sb/mul12 branch January 19, 2018 15:42
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5 participants