Computer freezes with parallel

Specific Domains Julia at Scale
1

Hi. I need to use parallel programming and I’ve been trying to play around with some basic parts. When I try to benchmark a simple threaded function, my laptop freezes for over five minutes and I resort to doing a hard shutdown.

using Distributed
using BenchmarkTools
using .Threads

function test_serial(m)
    u = zeros(Int64, m)
    for i in eachindex(u)
        u[i] = threadid()
    end
    return u
end

function test_threads(m)
    u = zeros(Int64, m)
    Threads.@threads for i in eachindex(u)
        u[i] = threadid()
    end
    return u
end

m = 100_000_000
@benchmark test_serial($m)
@benchmark test_threads($m)

When m above is 100M, the code finishes no problem. When m is 1B, test_serial will benchmark two samples, and it is finished in about 6 seconds, but test_threads freezes my laptop.

Doing Ctrl J K doesn’t stop it, nor does Ctrl Alt Del. I’m guessing this is because all of my processors are occupied. Is there any way I can perform these functions on arrays this long and benchmark them without risking the health of my laptop? Maybe a timeout? Tasks?

Thanks.

julia> @benchmark test_serial($m)   # m = 100M
BenchmarkTools.Trial:
  memory estimate:  762.94 MiB
  allocs estimate:  2
  --------------
  minimum time:     362.364 ms (3.82% GC)
  median time:      408.529 ms (15.66% GC)
  mean time:        410.735 ms (16.18% GC)
  maximum time:     445.156 ms (22.65% GC)
  --------------
  samples:          13
  evals/sample:     1

julia> @benchmark test_threads($m)   # m = 100M
BenchmarkTools.Trial:
  memory estimate:  762.94 MiB
  allocs estimate:  34
  --------------
  minimum time:     333.686 ms (0.13% GC)
  median time:      396.594 ms (15.47% GC)
  mean time:        396.439 ms (15.15% GC)
  maximum time:     436.842 ms (23.00% GC)
  --------------
  samples:          13
  evals/sample:     1

julia> @benchmark test_serial($m)    # m = 1B
BenchmarkTools.Trial:
  memory estimate:  7.45 GiB
  allocs estimate:  2
  --------------
  minimum time:     3.714 s (0.41% GC)
  median time:      6.760 s (0.54% GC)
  mean time:        6.760 s (0.54% GC)
  maximum time:     9.805 s (0.59% GC)
  --------------
  samples:          2
  evals/sample:     1