# Displaying amount of data sent to worker

**URL:** <https://discourse.julialang.org/t/displaying-amount-of-data-sent-to-worker/16134>\
**Category:** General Usage\
**Tags:** parallel\
**Created:** [October 10, 2018, 8:46pm UTC](https://discourse.julialang.org/t/displaying-amount-of-data-sent-to-worker/16134 "2018-10-10T20:46:55Z")\
**Posts on this page:** 1\
**Page:** 1

<div class="post-metadata">

**Author:** ![raminammour](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/raminammour/32/13572_2.png) [@raminammour](https://discourse.julialang.org/u/raminammour)\
**Post date:** [October 10, 2018, 8:46pm UTC](https://discourse.julialang.org/t/displaying-amount-of-data-sent-to-worker/16134/1 "2018-10-10T20:46:55Z")

</div>

Hello,

I am trying to produce an example that shows the subtle differences in writing code in a distributed setting. Here is a contrived example:

```julia
function bla1(rho,nc1)

    t1=@fetchfrom workers()[1] Sys.free_memory()
    
    pids= workers()[1:nc1]
    ss=zeros(nc1)
    
    @sync for i::Int in 1:nc1
        @async ss[i]=@fetchfrom pids[i] s=sum(view(rho,1:1,1:1)).*myid()
    end
    t2=@fetchfrom workers()[1] Sys.free_memory()
    
    @show (t1-t2)/2^30
    sum(ss)
end

 function bla2(rho,nc1)

    t1=@fetchfrom workers()[1] Sys.free_memory()
    
    ss=zeros(nc1)
    
    pids= workers()[1:nc1]
    
    @sync for i::Int in 1:nc1
        rhoI=view(rho,1:1,1:1)
        @async ss[i]=@fetchfrom pids[i] sum(rhoI).*myid()
    end
    t2=@fetchfrom workers()[1] Sys.free_memory()
    @show (t1-t2)/2^30
    sum(ss)
end 

```

The punchline is that `bla1` sends the whole array `rho`, and `bla2` only sends one entry. I can show that effect with:

```julia
@everywhere GC.gc_enable(false) #scary
rho=rand(10^7)
@time bla1(rho,3)
@tme bla2(rho,3)

(t1 - t2) / 2 ^ 30 = 0.22303009033203125
  0.131072 seconds (506 allocations: 32.297 KiB)

(t1 - t2) / 2 ^ 30 = 0.0
  0.002824 seconds (526 allocations: 32.016 KiB)

```

I feel that my solution is rather hacky, especially turning off garbage collection. What is the “Julian” way of doing it? Couldn’t figure it out with `@time,@allocated` …

Thanks!