mysterious performance gain

[Archibald via Digitalmars-d-learn]

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 )