This package provides the type PriorityChannel (the only exported name) that mimics Base.Channel, but where each element is associated with a priority. take! always returns the highest priority element. Internally, a heap is used to keep track of priorities. Example usage:
using PriorityChannels, Test
c = Channel(50)
pc = PriorityChannel(50)
for i = 1:50
e = rand(1:500)
put!(c,e)
put!(pc,e,e) # Assign same priority as element for testing purposes
end
elems = [take!(c) for i = 1:50]
pelems = [take!(pc) for i = 1:50]
@test !issorted(elems) # A regular Channel does not return ordered elements
@test issorted(pelems) # A PriorityChannel returns elements in priority orderput!(pc, element, priority::Real)lower number indicates a higher priority (default = 0).PriorityChannelcan not be unbuffered (of length 0) and must have a positive length.take!(pc)returns the highest priority item,PriorityChannelthus acts like a priority queue instead of a FIFO queue likeChanneldoes- Pretty much all other functionality should be the same, including all constructors.
To get maximum performance, initialize a concretely typed PriorityChannel. The constructor PriorityChannel(N) creates a channel of length N that holds type Any and have integer priorities. These types can be specified with the constructor PriorityChannel{ElemType,PrioType}(N), e.g., PriorityChannel{Int,Int}(N). There is a rather striking difference in performance between these two:
using PriorityChannels
N = 1_000_000
r = rand(1:1000, N);
const c1 = PriorityChannel(N)
const c2 = PriorityChannel{Int,Int}(N)
@time map(ri->put!(c1,ri,ri), r);
@time map(ri->put!(c2,ri,ri), r);
@time map(i->take!(c1), 1:N);
@time map(i->take!(c2), 1:N);
# Output after pre-compilation
julia> @time map(ri->put!(c1,ri,ri), r);
0.663640 seconds (4.33 M allocations: 150.086 MiB, 55.92% gc time)
julia> @time map(ri->put!(c2,ri,ri), r);
0.103298 seconds (60.23 k allocations: 12.643 MiB)
julia> @time map(i->take!(c1), 1:N);
3.282501 seconds (20.02 M allocations: 612.583 MiB, 27.25% gc time)
julia> @time map(i->take!(c2), 1:N);
0.313285 seconds (63.44 k allocations: 10.791 MiB, 4.67% gc time)