# Vectorized short circuit operator?

**URL:** <https://discourse.julialang.org/t/vectorized-short-circuit-operator/80336>\
**Category:** New to Julia\
**Tags:** question\
**Created:** [May 1, 2022, 4:41pm UTC](https://discourse.julialang.org/t/vectorized-short-circuit-operator/80336 "2022-05-01T16:41:49Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![Cevheriferd](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/cevheriferd/32/26792_2.png) [@Cevheriferd](https://discourse.julialang.org/u/Cevheriferd)\
**Post date:** [May 1, 2022, 4:41pm UTC](https://discourse.julialang.org/t/vectorized-short-circuit-operator/80336/1 "2022-05-01T16:41:49Z")

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Hi I was wondering if it is possible to apply a short circuit evaluation to 2 bitvectors. Let’s say I want to implement the **or** operator on 2 bitvectors, I can do that with `.|`. But this operator is not short circuited. I tried doing it with `.||` but this gave me an error. Is there any way around this?

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**Author:** ![Sukera](https://avatars.discourse-cdn.com/v4/letter/s/ce7236/32.png) [@Sukera](https://discourse.julialang.org/u/Sukera)\
**Post date:** [May 1, 2022, 4:45pm UTC](https://discourse.julialang.org/t/vectorized-short-circuit-operator/80336/2 "2022-05-01T16:45:22Z")

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This has been added, it’s included since Julia 1.7.:

[https://github.com/JuliaLang/julia/pull/39594](https://github.com/JuliaLang/julia/pull/39594)

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**Author:** ![DNF](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/dnf/32/10191_2.png) [@DNF](https://discourse.julialang.org/u/DNF)\
**Post date:** [May 1, 2022, 7:00pm UTC](https://discourse.julialang.org/t/vectorized-short-circuit-operator/80336/3 "2022-05-01T19:00:48Z")

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> [@Cevheriferd](#):
>
> Hi I was wondering if it is possible to apply a short circuit evaluation to 2 bitvectors.

You can do this, but it’s not a good idea. Short-circuit evaluation is there to avoid doing expensive calculations. Evaluating a bitwise `or` on two bitvectors is as cheap as it gets. Using a short-circuit version will introduce a branch, which is much more expensive, and prevent simd-vectorization.

Example:

```julia
julia> @btime (a .| b) setup=(a=bitrand(1024); b=bitrand(1024));
  39.919 ns (2 allocations: 224 bytes)

julia> @btime (a .|| b) setup=(a=bitrand(1024); b=bitrand(1024));
  1.030 μs (3 allocations: 4.41 KiB)

```

As you can see, the short-circuit version is 25x slower.

If, on the other hand, you have some expensive operations, short-circuiting pays off:

```julia
julia> using Primes

julia> @btime isodd.(a) .| isprime.(b) setup=(a=rand(10^3:10^4, 1024);b=rand(10^3:10^4, 1024));
  52.200 μs (127 allocations: 6.34 KiB)

julia> @btime isodd.(a) .|| isprime.(b) setup=(a=rand(10^3:10^4, 1024);b=rand(10^3:10^4, 1024));
  27.400 μs (57 allocations: 5.25 KiB)

```

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<div class="post-metadata">

**Author:** ![Cevheriferd](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/cevheriferd/32/26792_2.png) [@Cevheriferd](https://discourse.julialang.org/u/Cevheriferd)\
**Post date:** [May 1, 2022, 10:34pm UTC](https://discourse.julialang.org/t/vectorized-short-circuit-operator/80336/4 "2022-05-01T22:34:17Z")

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In my case it is quite relevant to have a short-circuit evaluation. This is because the second expression only gives an output if the first expression was false. A MWE is shown below:

```julia
using Distributions

a = rand(100)
b = rand(100)

c = (b .>= a) .|| (rand.(Bernoulli.(b./a)))

```

If the expression wasn’t short-circuited it would throw off an error in my case.

But thanks anyways!