# More upgrade, more slow down?

**URL:** <https://discourse.julialang.org/t/more-upgrade-more-slow-down/44458>\
**Category:** Performance\
**Created:** [August 6, 2020, 9:47pm UTC](https://discourse.julialang.org/t/more-upgrade-more-slow-down/44458 "2020-08-06T21:47:06Z")\
**Posts on this page:** 11\
**Page:** 1

<div class="post-metadata">

**Author:** ![paalon](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/paalon/32/5784_2.png) [@paalon](https://discourse.julialang.org/u/paalon)\
**Post date:** [August 6, 2020, 9:47pm UTC](https://discourse.julialang.org/t/more-upgrade-more-slow-down/44458/1 "2020-08-06T21:47:06Z")

</div>

Here is small benchmark code:

```julia
using BenchmarkTools

powersign(i) = ifelse(i % 2 == 0, 1, -1)

function leibniz(n)
    s = 0
    for i = 0:n
        s += powersign(i) / (2i + 1)
    end
    4s
end

n = 10^5
@benchmark leibniz(n)

```

and the result for multiple versions of Julia:

| | v1.0.2 | v1.1.0 | v1.4.2 | v1.5.0 |
| --- | --- | --- | --- | --- |
| min. | 173.301 | 186.601 | 199.325 | 204.133 |
| median | 179.043 | 186.773 | 199.453 | 204.204 |
| mean | 181.39 | 190.515 | 203.224 | 207.635 |
| max. | 369.603 | 536.942 | 464.297 | 424.371 |

(all units are μs)

Why later versions are slower?

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<div class="post-metadata">

**Author:** ![greg\_plowman](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/greg_plowman/32/8100_2.png) [@greg\_plowman](https://discourse.julialang.org/u/greg_plowman)\
**Post date:** [August 6, 2020, 10:55pm UTC](https://discourse.julialang.org/t/more-upgrade-more-slow-down/44458/2 "2020-08-06T22:55:46Z")

</div>

On my machine:

| | v1.0.5 | v1.1.1 | v1.2.0 | v1.3.1 | v1.4.2 | v1.5.0 |
| --- | --- | --- | --- | --- | --- | --- |
| minimum | 133.699 | 133.699 | 135.899 | 138.000 | 151.299 | 155.300 |
| median | 138.100 | 138.100 | 138.100 | 138.100 | 151.499 | 155.599 |
| mean | 140.788 | 145.842 | 141.484 | 150.637 | 154.460 | 159.071 |
| maximum | 736.101 | 674.799 | 659.399 | 639.000 | 715.301 | 767.301 |

And before someone mentions it, these timings are with interpolated benchmark argument:  
`@benchmark leibniz($n)`

---

<div class="post-metadata">

**Author:** ![tro3](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/tro3/32/12355_2.png) [@tro3](https://discourse.julialang.org/u/tro3)\
**Post date:** [August 7, 2020, 12:48am UTC](https://discourse.julialang.org/t/more-upgrade-more-slow-down/44458/3 "2020-08-07T00:48:56Z")

</div>

On mine, 1.5 looks a little slower, by roughly the same % as @greg_plowman :

**v1.3.0**

```julia
  minimum time: 117.799 μs (0.00% GC)
  median time: 120.200 μs (0.00% GC)
  mean time: 123.794 μs (0.00% GC)
  maximum time: 612.300 μs (0.00% GC)

```

**v1.5.0-beta1**

```julia
  minimum time: 134.399 μs (0.00% GC)
  median time: 135.399 μs (0.00% GC)
  mean time: 140.439 μs (0.00% GC)
  maximum time: 663.200 μs (0.00% GC)

```

---

<div class="post-metadata">

**Author:** ![paalon](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/paalon/32/5784_2.png) [@paalon](https://discourse.julialang.org/u/paalon)\
**Post date:** [August 7, 2020, 7:36am UTC](https://discourse.julialang.org/t/more-upgrade-more-slow-down/44458/4 "2020-08-07T07:36:36Z")

</div>

It seems to depend on CPU or OS.

| Intel Core i5-5250U / Ubuntu 18.04.5 | v1.0.5 | v1.1.1 | v1.2.0 | v1.3.1 | v1.4.2 | v1.5.0 |
| --- | --- | --- | --- | --- | --- | --- |
| minimum | 178.450 | 185.680 | 173.397 | 173.299 | 199.317 | 204.126 |
| median | 179.032 | 186.778 | 179.037 | 179.031 | 199.456 | 204.186 |
| mean | 182.881 | 189.929 | 183.635 | 183.448 | 203.279 | 208.294 |
| maximum | 354.239 | 404.800 | 370.055 | 368.178 | 391.177 | 401.432 |
| ratio of median to v1.0.5 | 1.000 | 1.043 | 1.000 | 1.000 | 1.114 | 1.141 |
| ratio of mean to v1.0.5 | 1.000 | 1.039 | 1.004 | 1.003 | 1.112 | 1.139 |

| Intel Core i7-7660U / macOS 10.15.6 | v1.0.5 | v1.1.1 | v1.2.0 | v1.3.1 | v.1.4.2 | v1.5.0 |
| --- | --- | --- | --- | --- | --- | --- |
| minimum | 117.882 | 126.724 | 125.325 | 125.344 | 150.376 | 136.314 |
| median | 125.338 | 127.701 | 125.335 | 125.356 | 150.405 | 137.267 |
| mean | 127.036 | 130.031 | 127.712 | 127.969 | 153.818 | 139.832 |
| maximum | 903.391 | 343.934 | 402.069 | 436.871 | 451.494 | 349.415 |
| ratio of median to v1.0.5 | 1.000 | 1.019 | 1.000 | 1.000 | 1.200 | 1.095 |
| ratio of mean to v1.0.5 | 1.000 | 1.024 | 1.005 | 1.007 | 1.211 | 1.101 |

```julia
using BenchmarkTools

function powersign(i)
	if i % 2 == 0
		1
	else
		-1
	end
end

function leibniz(n)
	s = 0
	for i = 0:n
		s += powersign(i) / (2i + 1)
	end
	4s
end

n = 10^5
result = @benchmark leibniz($n)
show(stdout, MIME"text/plain"(), result)

```

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<div class="post-metadata">

**Author:** ![jipolanco](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/jipolanco/32/12129_2.png) [@jipolanco](https://discourse.julialang.org/u/jipolanco)\
**Post date:** [August 7, 2020, 10:09am UTC](https://discourse.julialang.org/t/more-upgrade-more-slow-down/44458/5 "2020-08-07T10:09:39Z")

</div>

Can you try changing the initialisation of `s` from `s = 0` to `s = 0.0`? Note that the first case is type unstable, as `s` gets converted to `Float64` inside the loop.

If I make that change, runtimes drop by about 30% using Julia 1.5 on my machine. For instance, the median drops from 128 μs to 91 μs. I’m curious to see if older Julia versions are still faster in that case.

---

<div class="post-metadata">

**Author:** ![mihalybaci](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/mihalybaci/32/13528_2.png) [@mihalybaci](https://discourse.julialang.org/u/mihalybaci)\
**Post date:** [August 7, 2020, 11:20am UTC](https://discourse.julialang.org/t/more-upgrade-more-slow-down/44458/6 "2020-08-07T11:20:02Z")

</div>

On my 7-year old computer there is virtually no difference. I also find no performance difference between `s=0` and `s0.0` or `leibniz(n)` and `leibniz($n)`

Intel Corei7-4770 / MX Linux 19.1 |v1.0.5 |v1.5.0|  
|—|—|—|—|—|—|—|  
|minimum |359.830 |359.832 |  
|median |359.838 |359.839 |  
|mean |366.613 |368.265 |  
|maximum |684.231 |668.273 |  
|ratio of median to v1.0.5 |1.000 |1.0000002 |  
|ratio of mean to v1.0.5 |1.000 |1.0045 |

---

<div class="post-metadata">

**Author:** ![Juan](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/juan/32/7657_2.png) [@Juan](https://discourse.julialang.org/u/Juan)\
**Post date:** [August 8, 2020, 7:26pm UTC](https://discourse.julialang.org/t/more-upgrade-more-slow-down/44458/7 "2020-08-08T19:26:03Z")

</div>

What about v1.6.0?

---

<div class="post-metadata">

**Author:** ![stst](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/stst/32/17252_2.png) [@stst](https://discourse.julialang.org/u/stst)\
**Post date:** [August 8, 2020, 8:56pm UTC](https://discourse.julialang.org/t/more-upgrade-more-slow-down/44458/8 "2020-08-08T20:56:00Z")

</div>

Here’s a more compact way to write this function:

```julia
h(i) = (i%2==0 ? 1 : -1)/(2i+1)
leibniz2(n) = 4sum(h,0:n)

```

On my laptop with Julia 1.5.0, this is marginally faster (by about 1%) than the original function. Not sure why.

`leibniz2(10^5)` gives a result that differs in the 15th digit from `leibniz(10^5)`. Not sure which of the two is more accurate. This has probably to do with the non-associativity of float addition, as has been discussed many times here on Discourse.

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<div class="post-metadata">

**Author:** ![Henrique\_Becker](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/henrique_becker/32/15443_2.png) [@Henrique\_Becker](https://discourse.julialang.org/u/Henrique_Becker)\
**Post date:** [August 8, 2020, 9:38pm UTC](https://discourse.julialang.org/t/more-upgrade-more-slow-down/44458/9 "2020-08-08T21:38:05Z")

</div>

I think it would not be fair to compare to 1.6.0 yet, as it is not out.

---

<div class="post-metadata">

**Author:** ![mthelm85](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/mthelm85/32/224164_2.png) [@mthelm85](https://discourse.julialang.org/u/mthelm85)\
**Post date:** [August 8, 2020, 11:11pm UTC](https://discourse.julialang.org/t/more-upgrade-more-slow-down/44458/10 "2020-08-08T23:11:41Z")

</div>

> [@mihalybaci](#):
>
> On my 7-year old computer there is virtually no difference.

Virtually no difference for me as well:

```julia
Platform Info:
  OS: Windows (x86_64-w64-mingw32)
  CPU: AMD Ryzen 9 3950X 16-Core Processor
  WORD_SIZE: 64
  LIBM: libopenlibm
  LLVM: libLLVM-9.0.1 (ORCJIT, znver1)

```

v1.0.5:

```julia
BenchmarkTools.Trial:
  memory estimate: 0 bytes
  allocs estimate: 0
  --------------
  minimum time: 108.900 μs (0.00% GC)
  median time: 112.001 μs (0.00% GC)
  mean time: 113.777 μs (0.00% GC)
  maximum time: 155.100 μs (0.00% GC)
  --------------
  samples: 10000
  evals/sample: 1

```

v1.5.0:

```julia
BenchmarkTools.Trial:
  memory estimate: 0 bytes
  allocs estimate: 0
  --------------
  minimum time: 110.099 μs (0.00% GC)
  median time: 112.000 μs (0.00% GC)
  mean time: 113.242 μs (0.00% GC)
  maximum time: 154.400 μs (0.00% GC)
  --------------
  samples: 10000
  evals/sample: 1

```

---

<div class="post-metadata">

**Author:** ![Kruxigt](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/kruxigt/32/11694_2.png) [@Kruxigt](https://discourse.julialang.org/u/Kruxigt)\
**Post date:** [August 13, 2020, 10:48pm UTC](https://discourse.julialang.org/t/more-upgrade-more-slow-down/44458/11 "2020-08-13T22:48:27Z")

</div>

Are these performance differences extra pronounced for this particular function? Otherwise it seems really problematic…