• Archibald (8/8) Jul 18 2014 Hello,
• bearophile (4/6) Jul 18 2014 Not nearly enough info to answer. It looks fishy.
• John Colvin (2/10) Jul 18 2014 Which compiler? Which compiler flags? how are you benchmarking it?
• Archibald (5/19) Jul 18 2014 dmd 2.065 , -O and using std.datetime.StopWatch before and after
• =?UTF-8?B?QWxpIMOHZWhyZWxp?= (7/12) Jul 18 2014 Here is a wild guess: There is some undefined behavior because you are
• Wayne Anderson (4/12) Jul 18 2014 Perhaps some function your critical code calls might require

"Archibald" <archibald fake-mail.net> writes:

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 )

"bearophile" <bearophileHUGS lycos.com> writes:

Archibald:

 Any rational explaination to this? ( Seems unrelated to garbage 
 collection )

Not nearly enough info to answer. It looks fishy.

Bye,
bearophile

"John Colvin" <john.loughran.colvin gmail.com> writes:

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?

"Archibald" <archibald fake-mail.net> writes:

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.

=?UTF-8?B?QWxpIMOHZWhyZWxp?= <acehreli yahoo.com> writes:

On 07/18/2014 06:21 AM, Archibald wrote:

 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.

Here is a wild guess: There is some undefined behavior because you are 
accessing locations on the stack that don't belong to you. When you 
introduce 'direct', it shifts the contents of the stack and the bytes 
that are used unintentionally are now different, which change the way 
the loop behaves.

Ali

"Wayne Anderson" <wanderon comcast.net> writes:

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 )

Perhaps some function your critical code calls might require 
memory to be aligned to a particular offset (say 16 byte). What 
made you think of adding the unused array?