Julia newbie here!
I noticed a performance loss (by means of @benchmark from BenchmarkTools),
when a function returns a value versus when it does not.
Note: in the code snippet (see below) that I prepared to exemplify my
issue, there's also an increase in the number of allocations - which I
don't understand - when returning values.
However, in my own function (not included here), simulating a mathematical
model, there is no such a difference in the allocations but a ~5 times
performance degradation - as indicated by the output of @benchmark below:
(with output returned)
BenchmarkTools.Trial:
samples: 10000
evals/sample: 1
time tolerance: 5.00%
memory tolerance: 1.00%
memory estimate: 32.00 bytes allocs estimate: 1* minimum time: 62.56
μs (0.00% GC)
median time: 62.63 μs (0.00% GC)
mean time: 72.77 μs (0.00% GC)*
maximum time: 263.93 μs (0.00% GC)
(without output returned)
BenchmarkTools.Trial:
samples: 10000
evals/sample: 1
time tolerance: 5.00%
memory tolerance: 1.00%
memory estimate: 0.00 bytes allocs estimate: 0
* minimum time: 11.22 μs (0.00% GC)
median time: 13.58 μs (0.00% GC)
mean time: 14.19 μs (0.00% GC)*
maximum time: 119.73 μs (0.00% GC)
Is any gentle soul out there, patient enough and willing to explain whether
this might be a Julia's bug, or whether it is my brain's bug... ?
The code snippet is pasted below, including the output of @benchmark:
function test1()
a = rand(10000)
for k=1:10,
a = rand(10000)
end
end
function test2()
a = rand(10000)
for k=1:10,
a = rand(10000)
end
a[1]
end
> @benchmark test1() # without output returned
BenchmarkTools.Trial:
samples: 10000
evals/sample: 1
time tolerance: 5.00%
memory tolerance: 1.00%
memory estimate: 860.41 kb
allocs estimate: 44
* minimum time: 210.01 μs (0.00% GC)
median time: 292.29 μs (0.00% GC)
mean time: 483.24 μs (20.95% GC)*
maximum time: 26.80 ms (93.95% GC)
> @benchmark test2() # with output returned
BenchmarkTools.Trial:
samples: 3398
evals/sample: 1
time tolerance: 5.00%
memory tolerance: 1.00%
memory estimate: 2.37 mb
allocs estimate: 100045
* minimum time: 704.49 μs (0.00% GC)
median time: 896.99 μs (0.00% GC)
mean time: 1.46 ms (17.55% GC)*
maximum time: 37.16 ms (36.87% GC)
Thank you all.
