# Memory allocation issue with iterator type
**URL:** https://discourse.julialang.org/t/memory-allocation-issue-with-iterator-type/5715
**Category:** General Usage
**Tags:** question, memory-allocation
**Created:** [September 4, 2017, 5:22pm UTC](https://discourse.julialang.org/t/memory-allocation-issue-with-iterator-type/5715 "2017-09-04T17:22:42Z")
**Posts on this page:** 5
**Page:** 1
### Author:  [@juliohm](https://discourse.julialang.org/u/juliohm)
#### Post date: [September 4, 2017, 5:22pm UTC](https://discourse.julialang.org/t/memory-allocation-issue-with-iterator-type/5715/1 "2017-09-04T17:22:42Z")
Happy labor day!
Anyone around that could help with the following issue? Consider this simple snippet:
```julia
# DOMAIN
abstract type AbstractDomain{T<:Real,N} end
struct RegularGrid{T<:Real,N} <: AbstractDomain{T,N}
dims::Dims{N}
origin::NTuple{N,T}
spacing::NTuple{N,T}
function RegularGrid{T,N}(dims, origin, spacing) where {N,T<:Real}
@assert all(dims .> 0) "dimensions must be positive"
@assert all(spacing .> 0) "spacing must be positive"
new(dims, origin, spacing)
end
end
RegularGrid{T}(dims::Dims{N}) where {N,T<:Real} =
RegularGrid{T,N}(dims, (zeros(T,length(dims))...), (ones(T,length(dims))...))
RegularGrid{T}(dims::Vararg{<:Integer,N}) where {N,T<:Real} = RegularGrid{T}(dims)
npoints(grid::RegularGrid) = prod(grid.dims)
# PATH
abstract type AbstractPath{D<:AbstractDomain} end
struct RandomPath{D<:AbstractDomain} <: AbstractPath{D}
domain::D
permut::Vector{Int}
function RandomPath{D}(domain, permut) where {D<:AbstractDomain}
@assert length(permut) == npoints(domain) "incorrect dimension"
new(domain, permut)
end
end
RandomPath(domain) = RandomPath{typeof(domain)}(domain, randperm(npoints(domain)))
Base.start(p::RandomPath) = Base.start(p.permut)
Base.next(p::RandomPath, state) = Base.next(p.permut, state)
Base.done(p::RandomPath, state) = Base.done(p.permut, state)
Base.length(p::RandomPath) = npoints(p.domain)
# MAIN SCRIPT
grid = RegularGrid{Float64}(100,100)
path = RandomPath(grid)
for location in path
location
end
Profile.clear_malloc_data()
for location in path
location
end
```
All it does is loop over a grid in random order. However, I am wondering why the `done` method of the iterator is allocating memory:
```julia
- struct RandomPath{D<:AbstractDomain} <: AbstractPath{D}
- domain::D
- permut::Vector{Int}
-
- function RandomPath{D}(domain, permut) where {D<:AbstractDomain}
0 @assert length(permut) == npoints(domain) "incorrect dimension"
0 new(domain, permut)
- end
- end
0 RandomPath(domain) = RandomPath{typeof(domain)}(domain, randperm(npoints(domain)))
- Base.start(p::RandomPath) = Base.start(p.permut)
0 Base.next(p::RandomPath, state) = Base.next(p.permut, state)
654016 Base.done(p::RandomPath, state) = Base.done(p.permut, state)
- Base.length(p::RandomPath) = npoints(p.domain)
```
cc: @kristoffer.carlsson, @cstjean
---
### Author:  [@ChrisRackauckas](https://discourse.julialang.org/u/ChrisRackauckas)
#### Post date: [September 4, 2017, 5:26pm UTC](https://discourse.julialang.org/t/memory-allocation-issue-with-iterator-type/5715/2 "2017-09-04T17:26:17Z")
> [@juliohm](#):
>
> Consider this simple snippet:
What @kristoffer.carlsson is saying is that this is not a simple snippet. It requires understanding your entire code base. You’re essentially asking for contributors, which is fine, but I wouldn’t expect a lot of random people to start jumping in to contribute for you off of this. A simple example should isolate what’s going on to not use a bunch of functionality in the package.
But in this case we know that the allocations are because you have inferrability issues that have already been mentioned, at least in part due to untyped fields in types which has already been shown.
---
### Author:  [@juliohm](https://discourse.julialang.org/u/juliohm)
#### Post date: [September 4, 2017, 5:34pm UTC](https://discourse.julialang.org/t/memory-allocation-issue-with-iterator-type/5715/3 "2017-09-04T17:34:27Z")
Thank you @ChrisRackauckas, I am not asking for contributions, sorry if it is looking like it is.
I will copy/paste the definitions inside of the package to outside of it and see if it makes a difference.
---
### Author:  [@juliohm](https://discourse.julialang.org/u/juliohm)
#### Post date: [September 4, 2017, 10:47pm UTC](https://discourse.julialang.org/t/memory-allocation-issue-with-iterator-type/5715/4 "2017-09-04T22:47:05Z")
Fixed the example @ChrisRackauckas, it is self-contained now.
---
### Author:  [@cstjean](https://discourse.julialang.org/u/cstjean)
#### Post date: [September 5, 2017, 12:42am UTC](https://discourse.julialang.org/t/memory-allocation-issue-with-iterator-type/5715/5 "2017-09-05T00:42:02Z")
That works! But the way it’s reduced now, it looks like using globals causes the allocation. If I rewrite it as
```julia
function f(path)
for location in path
location
end
end
using BenchmarkTools
@benchmark f(path)
```
then it reports no allocation.