Parallel julia code

New to Julia
22

In modern Julia, I would probably prefer to use threads for this.

Start julia with julia --threads auto.

function count_heads(trials)
    flips = rand(Bool, trials)
    num_heads = sum(flips)
    return num_heads
end

trial_counts = [1000, 2000, 3000, 4000]
head_counts = zeros(Int, length(trial_counts))
Threads.@threads for i in eachindex(trial_counts)
    head_counts[i] = count_heads(trial_counts[i])
end

println("Trial Counts:", trial_counts)
println("Head Counts:", head_counts)

Executing the code in the Julia REPL outputs the following.

julia> Threads.nthreads()
6

julia> function count_heads(trials)
           flips = rand(Bool, trials)
           num_heads = sum(flips)
           return num_heads
       end
count_heads (generic function with 1 method)

julia> trial_counts = [1000, 2000, 3000, 4000]
4-element Vector{Int64}:
 1000
 2000
 3000
 4000

julia> head_counts = zeros(Int, length(trial_counts))
4-element Vector{Int64}:
 0
 0
 0
 0

julia> Threads.@threads for i in eachindex(trial_counts)
           head_counts[i] = count_heads(trial_counts[i])
       end

julia> println("Trial Counts:", trial_counts)
Trial Counts:[1000, 2000, 3000, 4000]

julia> println("Head Counts:", head_counts)
Head Counts:[486, 1016, 1489, 2006]

To format code, do the following in this forum.

```julia
function foo()
    println("Hello world")
end
```

```julia-repl
julia> foo()
Hello world
```

Note to others, you can use more backticks to escape triple backticks:

````
```julia
function foo()
    println("Hello world")
end
```
````
7 Likes
23

I agree with @mkitti It is easy to get frustrated and angry here. Take a step back - everyone here is very friendly. Maybe you could use four pieces of paper and pretend these are threads of computation of distributed processes. Maybe you think better by using a whiteboard.
Or talk to your cat. Cats are very wise and are excellent programmers.

2 Likes