It gets even faster if you make the slight change shown below in red:
$CompilationTarget = "C";
f = Compile[{{x, _Real, 1}, {min, _Real}, {max, _Real}},
Module[{count = 0},
Do[If[min <= i <= max, count++], {i, x}]; count],
"RuntimeOptions" -> "Speed"];
On Monday, July 21, 2014 at 5:29:02 AM UTC-5, [email protected] wrote:
>
> On Saturday, January 25, 2014 8:41:08 PM UTC+1, Johan Sigfrids wrote:
>>
>> On Saturday, January 25, 2014 9:24:17 PM UTC+2, Jason Merrill wrote:
>>>
>>> mma> data = RandomReal[1.,1*^7]; min = .2; max = .3;
>>> mma> Total@Unitize@Clip[data,{min,max},{0,0}]
>>>
>>> I claim that it takes *a lot* of experience to know that that is the
>>> code that is going to be fast, compared to the other 15 approaches people
>>> bring up there, because the mapping between Mathematica's core constructs
>>> and the machine's core constructs is far more complicated and indirect than
>>> for Julia.
>>>
>>> In contrast, it doesn't take deep familiarity with Julia's standard
>>> library to come up with about the fastest way to write this operation.
>>>
>>> julia> function count_range(arr, min, max)
>>> count = 0
>>> for elt in arr
>>> if min < elt < max count += 1 end
>>> end
>>> count
>>> end
>>>
>>> It takes more than one line to write, but it's *obvious*. My Mathematica
>>> license is expired these days, so I can't run the benchmark, but I bet it
>>> also smokes the fast solution in Mathematica.
>>>
>>
>> Having a Mathematica license and being curious I compared them. The Julia
>> version is roughly 10x faster than the Mathematica version.
>>
>
> I compared with Mathematica 9. Total@Unitize@Clip[data,{min,max},{0,0}]
> was for me roughly 3x slower than the Julia version; which sounds
> reasonable since Total, Unitize and Clip run once though the data. In
> Mathematica 9 you also have the option to compile to C, which then runs as
> fast as the Julia version:
>
> $CompilationTarget = "C";
> f = Compile[{{x, _Real, 1}, {min, _Real}, {max, _Real}},
> Module[{count = 0},
> Do[If[min <= x[[i]] <= max, count++], {i, Length@x}]; count],
> "RuntimeOptions" -> "Speed"];
>
