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alternative fix for mul! #34394

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alternative fix for mul! #34394

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20f2720
alternative fix for mul!
daviehh Jan 15, 2020
283fd25
alt MulAddMul
daviehh Jan 16, 2020
a48dc5a
Merge branch 'alt_mul'
daviehh Jan 16, 2020
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27 changes: 16 additions & 11 deletions stdlib/LinearAlgebra/src/generic.jl
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Original file line number Diff line number Diff line change
Expand Up @@ -20,22 +20,28 @@ julia> MulAddMul(12, 34)(56, 78) == 56 * 12 + 78 * 34
true
```
"""
struct MulAddMul{ais1, bis0, TA, TB}
struct MulAddMul{TA, TB}
alpha::TA
beta::TB
ais1::Bool
bis0::Bool
end

MulAddMul(alpha::TA, beta::TB) where {TA, TB} =
MulAddMul{isone(alpha), iszero(beta), TA, TB}(alpha, beta)
MulAddMul{TA, TB}(alpha, beta, isone(alpha), iszero(beta))

MulAddMul() = MulAddMul(true, false)

@inline (::MulAddMul{true})(x) = x
@inline (p::MulAddMul{false})(x) = x * p.alpha
@inline (::MulAddMul{true, true})(x, _) = x
@inline (p::MulAddMul{false, true})(x, _) = x * p.alpha
@inline (p::MulAddMul{true, false})(x, y) = x + y * p.beta
@inline (p::MulAddMul{false, false})(x, y) = x * p.alpha + y * p.beta
@inline (p::MulAddMul)(x) = p.ais1 ? x : x * p.alpha

@inline function (p::MulAddMul)(x, y)
x_mul_a = p.ais1 ? x : x * p.alpha
if p.bis0
return x_mul_a
else
return x_mul_a + y * p.beta
end
end

"""
_modify!(_add::MulAddMul, x, C, idx)
Expand All @@ -59,14 +65,13 @@ julia> C
123.0
```
"""
@inline @propagate_inbounds function _modify!(p::MulAddMul{ais1, bis0},
x, C, idx′) where {ais1, bis0}
@inline @propagate_inbounds function _modify!(p::MulAddMul, x, C, idx′)
# `idx′` may be an integer, a tuple of integer, or a `CartesianIndex`.
# Let `CartesianIndex` constructor normalize them so that it can be
# used uniformly. It also acts as a workaround for performance penalty
# of splatting a number (#29114):
idx = CartesianIndex(idx′)
if bis0
if p.bis0
C[idx] = p(x)
else
C[idx] = p(x, C[idx])
Expand Down