ParallelIncrements

ParallelIncrements.jl contains some code for benchmarking and demonstrating the overhead of atomic operation on arrays.

Usage:

using ParallelIncrements
suite = ParallelIncrements.benchsuite()  # BenchmarkTools.BenchmarkGroup
result = run(suite; verbose = true)

prints something like

2-element BenchmarkTools.BenchmarkGroup:
  tags: []
  "n=1000" => 1-element BenchmarkTools.BenchmarkGroup:
          tags: []
          "m=1000000" => 2-element BenchmarkTools.BenchmarkGroup:
                  tags: []
                  "nonatomic" => Trial(570.088 μs)
                  "atomic" => Trial(5.701 ms)
  "single" => 2-element BenchmarkTools.BenchmarkGroup:
          tags: []
          "nonatomic" => Trial(35.000 ns)
          "atomic" => Trial(4.888 μs)

atomic uses atomic instructions; nonatomic uses standard instructions.

n=1000/m=1000000 benchmark increments random m indices in a vector of length n. Atomic operation is 10x slower.

single benchmark increments a single location in an array 1000 times. The difference is much more drastic (~140x) presumably because the compiler elides the loads and stores for the nonatomic case.