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unexpected copying
From: |
Paul Kienzle |
Subject: |
unexpected copying |
Date: |
Mon, 12 Jun 2006 11:38:36 -0400 |
User-agent: |
Mutt/1.2.5.1i |
Hi,
I'm getting unexpected quadratic behaviour from an assignment
to an array after reshape in 2.9.5 (Debian):
S=T=[100:100:800];
for i=1:length(S),
k=S(i); A=rand(k);
tic; A=reshape(A,k*10,k/10); A(1,1)=2; T(i) = toc;
end
[P,R] = polyfit(S,T,2);
plot(S,T,S,polyval(P,S))
Presumably the array is being copied. Without the
assigment A(1,1)=2 the time is constant, so the copy isn't
happening in reshape. Similarly, without the reshape the
time is constant, so the copy isn't happening in the assignment.
I wasn't able to demonstrate a memory leak either, so it is
not a simple reference counting issue.
Any guesses?
- Paul
- unexpected copying,
Paul Kienzle <=