When in doubt, use @benchmark! On Tue, Nov 1, 2016 at 5:49 AM, Johan Sigfrids <johan.sigfr...@gmail.com> wrote:
> Given that allocating an array for 50 Ints, filling it up, and then > summing it all together probably takes less than a microsecond, any > difference between allocating and not allocating will disappears in the > noise. As Yichao Yu mentions, what you end up measuring is the time it > takes to setup the computation. This is a case where using the > BenchmarkTools can be really helpful. > > julia> using BenchmarkTools > > julia> @benchmark sum([2*t for t in 1:2:100]) > BenchmarkTools.Trial: > samples: 10000 > evals/sample: 907 > time tolerance: 5.00% > memory tolerance: 1.00% > memory estimate: 560.00 bytes > allocs estimate: 2 > minimum time: 121.00 ns (0.00% GC) > median time: 131.00 ns (0.00% GC) > mean time: 162.82 ns (10.91% GC) > maximum time: 2.45 μs (0.00% GC) > > julia> @benchmark sum(2*t for t in 1:2:100) > BenchmarkTools.Trial: > samples: 10000 > evals/sample: 962 > time tolerance: 5.00% > memory tolerance: 1.00% > memory estimate: 80.00 bytes > allocs estimate: 3 > minimum time: 86.00 ns (0.00% GC) > median time: 90.00 ns (0.00% GC) > mean time: 107.20 ns (6.99% GC) > maximum time: 3.64 μs (95.05% GC) > > > On Monday, October 31, 2016 at 9:42:14 PM UTC+2, Jesse Jaanila wrote: >> >> Hi, >> >> I was experimenting with the new 0.5 features and they are great! But to >> my surprise, >> the generator syntax doesn't work as I'm expecting. Let's say I want to >> calculate >> some summation. With the old syntax I could do >> >> @time sum([2*t for t in 1:2:100]) >> 0.015104 seconds (13.80 k allocations: 660.366 KB) >> >> that allocates the array within the summation. Now I thought this would a >> prime example >> where the memory overhead could be decreased by using the new notation >> i.e. >> >> @time sum(2*t for t in 1:2:100) >> 0.019215 seconds (18.98 k allocations: 785.777 KB) >> >> ,but generator syntax performs slightly worse. Also if we want find the >> maximum we would do >> >> julia> @time maximum([2*t for t in 1:2:100]) >> 0.015182 seconds (12.90 k allocations: 606.166 KB) >> 198 >> >> julia> @time maximum(2*t for t in 1:2:100) >> 0.019935 seconds (18.74 k allocations: 772.180 KB) >> 198 >> >> Have I understood the new generator syntax incorrectly or should the new >> syntax perform >> better in these code snippet examples? >> >> >> >> >> >> >>
