mysterious performance gain

Archibald via Digitalmars-d-learn digitalmars-d-learn at puremagic.com
Fri Jul 18 10:02:27 PDT 2014


On Friday, 18 July 2014 at 15:55:29 UTC, John Colvin wrote:
> On Friday, 18 July 2014 at 13:21:09 UTC, Archibald wrote:
>> Hello,
>> So I have this big, performance critical function that takes 
>> about 9 seconds to execute. If I add :
>>
>> double[] direct = new double[2];
>>
>> ... at the beggining of the function, with no further 
>> reference to this array, suddenly it takes only 8 seconds.
>>
>> Any rational explaination to this? ( Seems unrelated to 
>> garbage collection )
>
> Which compiler? Which compiler flags? how are you benchmarking 
> it?

dmd 2.065 , -O and using std.datetime.StopWatch before and after 
function call.
I tried to narrow down the "problem" but doesn't look easy.
I guess never mind that.


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