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Curious
Posts:
2,309
Registered:
12/6/04


Re: Speed up
Posted:
Mar 8, 2014 2:20 PM


"Ghulaam " <golem.mason@gmail.com> wrote in message <lfff1n$ic2$1@newscl01ah.mathworks.com>... > Hi would appreciate some assistance in speeding up the following code via vectorisation > > for h = 0.9:0.05:1.8 > for iv = 0.2:0.1:2 > y(1)=iv; > for k = 2:520 > y(k) = y(k1)+h*(y(k1)+0.5*h*y(k1)*(1y(k1)))*(1y(k1)0.5*h*y(k1)*(1y(k1))); > end > plot(h*(ones(20,1)), y(501:520),'*'), set(gca(),"auto_clear","off") > end > end > > title('Modified Euler') > xlabel('h'), ylabel('last 20 y') > > set(gca(),"grid",[1 1]), set(gca(),"auto_clear","on")
First, have you preallocated y?
Second, try simplifying the expression, for example the first two terms are simply:
y(k) = y(k1)*(1 + h) + ...
Once simplified, maybe you can find a way to use CUMSUM.



