COOvsCSC.jl

A = sprand(65535, 65500, 1e-5)
v = rand(65500)

function foo(A, v)
  b = zeros(size(A,1))
  rows = rowvals(A)
  vals = nonzeros(A)
  m, n = size(A)
  for i = 1:n
     @inbounds @simd for j in nzrange(A, i)
        row = rows[j]
        val = vals[j]
        b[row] += val * v[i]
     end
  end
  b
end

# COO？
idxcoo = Tuple{Int,Int}[]
valcoo = Float64[]
rows = rowvals(A)
vals = nonzeros(A)
m, n = size(A)
for i = 1:n
   for j in nzrange(A, i)
      row = rows[j]
      val = vals[j]
      push!(idxcoo, (row,i))
      push!(valcoo, val)
   end
end

function bar(idxcoo, valcoo, v, N)
    b = zeros(N)
    @inbounds @simd for n in eachindex(idxcoo)
        i, j = idxcoo[n]
        val = valcoo[n]
        b[i] += val * v[j]
    end
    b
end


using BenchmarkTools

@benchmark foo($A, $v) # -> 687
@benchmark bar($idxcoo, $valcoo, $v, size(A,1)) # -> 193

foo2() = [foo(A,v) for i = 1:1000]
bar2() = [bar(idxcoo, valcoo, v, size(A,1)) for i = 1:1000]

foo(A, v) == bar(idxcoo, valcoo, v, size(A,1))

using Profile

Profile.clear()
@profiler foo2()

Profile.clear()
@profiler bar2()