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slowdown with Val dispatch in v0.6 #21730

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ghost opened this issue May 6, 2017 · 6 comments
Closed

slowdown with Val dispatch in v0.6 #21730

ghost opened this issue May 6, 2017 · 6 comments
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@JeffBezanson
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performance Must go faster regression Regression in behavior compared to a previous version

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@ghost
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ghost commented May 6, 2017 

using BenchmarkTools
const f32 = 0
jltype(::Val{f32}) = Float32
get_type(i) = jltype(Val{i}())
@benchmark get_type(f32)

Is almost hundred times slower with 0.6 (40 ns with v0.5 vs 4 μs with v0.6). Causes significant slowdown in ArrayFIre.jl package when types have to inferred.
@timholy
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timholy commented May 7, 2017

That's a textbook example of misusing Val. https://docs.julialang.org/en/latest/manual/performance-tips.html#Types-with-values-as-parameters-1. Not that it wouldn't be good to fix the performance difference, but it's fundamentally non-inferrable.

@yuyichao yuyichao changed the title slowdown with Val type inference in v0.6 slowdown with Val dispatch in v0.6 May 7, 2017
@JeffBezanson JeffBezanson added performance Must go faster regression Regression in behavior compared to a previous version labels May 7, 2017
@JeffBezanson
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Seems related to #21323. In this case since there is a 0-arg constructor we're forced to dispatch on the type instead of other arguments.

@JeffBezanson JeffBezanson self-assigned this May 7, 2017
JeffBezanson added a commit that referenced this issue May 9, 2017
@JeffBezanson
speed up 0-arg constructor dispatch. fixes #21730
cb150a8 
For the `Type` method table, use the top-level `any` cache to split
based on whether the first argument is a leaf type. Leaf types
use the hash table, and non-leaf types skip the first argument and
try to split on the second argument instead.
@JeffBezanson JeffBezanson mentioned this issue May 9, 2017
Closed
JeffBezanson added a commit that referenced this issue May 9, 2017
@JeffBezanson
speed up 0-arg constructor dispatch. fixes #21730
d5a7ea0 
For the `Type` method table, use the top-level `any` cache to split
based on whether the first argument is a leaf type. Leaf types
use the hash table, and non-leaf types skip the first argument and
try to split on the second argument instead.
JeffBezanson added a commit that referenced this issue May 17, 2017
@JeffBezanson
speed up 0-arg constructor dispatch. fixes #21730
c797a92 
For the `Type` method table, use the top-level `any` cache to split
based on whether the first argument is a leaf type. Leaf types
use the hash table, and non-leaf types skip the first argument and
try to split on the second argument instead.
JeffBezanson added a commit that referenced this issue Jun 1, 2017
@JeffBezanson
speed up 0-arg constructor dispatch. fixes #21730
1dfc4d3 
For the `Type` method table, use the top-level `any` cache to split
based on whether the first argument is a leaf type. Leaf types
use the hash table, and non-leaf types skip the first argument and
try to split on the second argument instead.
JeffBezanson added a commit that referenced this issue Jun 30, 2017
@JeffBezanson
speed up 0-arg constructor dispatch. fixes #21730
aaaf9f4 
For the `Type` method table, use the top-level `any` cache to split
based on whether the first argument is a leaf type. Leaf types
use the hash table, and non-leaf types skip the first argument and
try to split on the second argument instead.
JeffBezanson added a commit that referenced this issue Jul 11, 2017
@JeffBezanson
speed up 0-arg constructor dispatch. fixes #21730
28c1432 
Uses the `any` cache to skip all non-leaf slots when a later slot
is splittable.
JeffBezanson added a commit that referenced this issue Jul 11, 2017
@JeffBezanson
speed up 0-arg constructor dispatch. fixes #21730
74a9a44 
Uses the `any` cache to skip all non-leaf slots when a later slot
is splittable.
JeffBezanson added a commit that referenced this issue Jul 12, 2017
@JeffBezanson
speed up 0-arg constructor dispatch. fixes #21730
4146abc 
Uses the `any` cache to skip all non-leaf slots when a later slot
is splittable.
JeffBezanson added a commit that referenced this issue Jul 13, 2017
@JeffBezanson
speed up 0-arg constructor dispatch. fixes #21730
63e1d9b 
Uses the `any` cache to skip all non-leaf slots when a later slot
is splittable.
JeffBezanson added a commit that referenced this issue Jul 14, 2017
@JeffBezanson
speed up 0-arg constructor dispatch. fixes #21730
6c673eb 
Uses the `any` cache to skip all non-leaf slots when a later slot
is splittable.
JeffBezanson added a commit that referenced this issue Jul 14, 2017
@JeffBezanson
speed up 0-arg constructor dispatch. fixes #21730
ecff624 
Uses the `any` cache to skip all non-leaf slots when a later slot
is splittable.
@musm
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musm commented Aug 4, 2017

closed by ecff624 ?

@martinholters
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martinholters commented Aug 4, 2017 •
edited
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No. I have 44ns on 0.5, 6μs on 0.6 and 1.8μs on master. So it has improved since 0.6, but it's nowhere close to 0.5.

EDIT: D'oh, that hasn't been merged yet, so it cannot fix the issue on master.

@KristofferC
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900 ns now.

@KristofferC KristofferC mentioned this issue Nov 1, 2018
Closed
@KristofferC KristofferC mentioned this issue Jun 22, 2020
Closed
@oscardssmith
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160ns now. Is that good enough to close?

@vtjnash vtjnash closed this as completed Dec 8, 2020
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@vtjnash @JeffBezanson @KristofferC @timholy @musm @oscardssmith @martinholters