# Performance of log.(x)

**URL:** <https://discourse.julialang.org/t/performance-of-log-x/23039>\
**Category:** General Usage\
**Tags:** performance, broadcast\
**Created:** [April 11, 2019, 2:26am UTC](https://discourse.julialang.org/t/performance-of-log-x/23039 "2019-04-11T02:26:05Z")\
**Posts on this page:** 1\
**Showing post:** 2

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**Author:** ![rdeits](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/rdeits/32/286_2.png) [@rdeits](https://discourse.julialang.org/u/rdeits)\
**Post date:** [April 11, 2019, 2:55am UTC](https://discourse.julialang.org/t/performance-of-log-x/23039/2 "2019-04-11T02:55:12Z")

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Welcome!

My guess would be that you’re getting SIMD operations in numpy but not in Julia. Interestingly, I can’t reproduce your timing numbers; instead, my Julia timing roughly matches yours, but my numpy results are about 10X slower:

```julia
julia> x = randn(10000) .+ 5;

julia> @benchmark log.($x)
BenchmarkTools.Trial: 
  memory estimate: 78.20 KiB
  allocs estimate: 2
  --------------
  minimum time: 57.371 μs (0.00% GC)
  median time: 59.739 μs (0.00% GC)
  mean time: 67.735 μs (7.25% GC)
  maximum time: 35.763 ms (99.67% GC)
  --------------
  samples: 10000
  evals/sample: 1

```

```julia
In [3]: x = np.random.randn(10000) + 5

In [4]: %timeit np.log(x)
173 µs ± 5.53 µs per loop (mean ± std. dev. of 7 runs, 10000 loops each)

```

There was a related discussion of SIMD optimizations for logs here: [Performance of logarithm calculation (when not to use the dot operator?) - #4 by kristoffer.carlsson](https://discourse.julialang.org/t/performance-of-logarithm-calculation-when-not-to-use-the-dot-operator/10504/4) although I’m afraid I don’t know enough about the details to be sure if it’s still relevant.

You also might want to consider making a separate thread for this discussion, as it’s only tangentially related to the topic of the original post (which was simply a question of syntax, not of performance optimization).

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_[View the full topic](https://discourse.julialang.org/t/performance-of-log-x/23039)._