# Container broadcasting memory/performance hit in 0.6?
**URL:** https://discourse.julialang.org/t/container-broadcasting-memory-performance-hit-in-0-6/2647
**Category:** General Usage
**Tags:** broadcast
**Created:** [March 13, 2017, 11:09pm UTC](https://discourse.julialang.org/t/container-broadcasting-memory-performance-hit-in-0-6/2647 "2017-03-13T23:09:25Z")
**Posts on this page:** 3
**Page:** 1
### Author:  [@marius311](https://discourse.julialang.org/u/marius311)
#### Post date: [March 13, 2017, 11:09pm UTC](https://discourse.julialang.org/t/container-broadcasting-memory-performance-hit-in-0-6/2647/1 "2017-03-13T23:09:25Z")
I don’t understand why the latter two calls below use twice the memory and are much slower than the first call. I had thought this type of broadcasting should work efficiently now but maybe I misunderstood? I’ve checked both on v0.6.0-pre.alpha as well as master.
```julia
$ julia
_
_ _ _(_)_ | A fresh approach to technical computing
(_) | (_) (_) | Documentation: http://docs.julialang.org
_ _ _| |_ __ _ | Type "?help" for help.
| | | | | | |/ _ | |
| | |_| | | | (_| | | Version 0.6.0-pre.alpha.137 (2017-03-13 14:27 UTC)
_/ |\ __'_|_|_|\__'_| | Commit a132ae2* (0 days old master)
|__/ | x86_64-linux-gnu
julia> a = b = rand(100,100);
julia> using BenchmarkTools
julia> @benchmark a .+ b .+ a
BenchmarkTools.Trial:
memory estimate: 79.33 KiB
allocs estimate: 27
--------------
minimum time: 23.414 μs (0.00% GC)
median time: 27.117 μs (0.00% GC)
mean time: 31.874 μs (8.69% GC)
maximum time: 1.079 ms (92.62% GC)
--------------
samples: 10000
evals/sample: 1
time tolerance: 5.00%
memory tolerance: 1.00%
julia> @benchmark (a,) .* (b,) .* (a,)
BenchmarkTools.Trial:
memory estimate: 156.45 KiB
allocs estimate: 7
--------------
minimum time: 75.679 μs (0.00% GC)
median time: 84.202 μs (0.00% GC)
mean time: 179.888 μs (3.84% GC)
maximum time: 23.779 ms (0.00% GC)
--------------
samples: 10000
evals/sample: 1
time tolerance: 5.00%
memory tolerance: 1.00%
julia> @benchmark [a] .* [b] .* [a]
BenchmarkTools.Trial:
memory estimate: 158.34 KiB
allocs estimate: 56
--------------
minimum time: 124.935 μs (0.00% GC)
median time: 134.950 μs (0.00% GC)
mean time: 151.803 μs (4.55% GC)
maximum time: 6.196 ms (0.00% GC)
--------------
samples: 10000
evals/sample: 1
time tolerance: 5.00%
memory tolerance: 1.00%
```
---
### Author:  [@yuyichao](https://discourse.julialang.org/u/yuyichao)
#### Post date: [March 13, 2017, 11:19pm UTC](https://discourse.julialang.org/t/container-broadcasting-memory-performance-hit-in-0-6/2647/2 "2017-03-13T23:19:26Z")
1. You are not benchmarking what you think you are benchmarking. You are benchmarking global variable access and dynamic dispatch.
2. It’s unclear what you are comparing. The second and the third benchmark doesn’t use fusion at all (I mean not for the actual 100x100 addition).
---
### Author:  [@marius311](https://discourse.julialang.org/u/marius311)
#### Post date: [March 13, 2017, 11:25pm UTC](https://discourse.julialang.org/t/container-broadcasting-memory-performance-hit-in-0-6/2647/3 "2017-03-13T23:25:07Z")
> You are not benchmarking what you think you are benchmarking. You are benchmarking global variable access and dynamic dispatch.
Ah I see, thanks, I had thought @benchmark took care of this.
> It’s unclear what you are comparing. The second and the third benchmark doesn’t use fusion at all (I mean not for the actual 100x100 addition).
Ok, I was under the impression broadcasting over tuples “forwarded” the fusion to the contents as well, but I see now that it just does normal addition over the contents, hence the creation of the temporary arrays that double the memory.