|Jack Brennen on Thu, 16 Feb 2012 01:19:13 +0100|
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|Re: Question on subst(), deferred evaluation and trap()|
On 2/15/2012 12:25 PM, Bill Allombert wrote:
So far, the best I've come up with is: V=[1/(x-1),1/(x-2),1/(x-3)]; And then instead of a simple subst() on V, I use: N=3;vector(#V,j,trap(,0,subst(V[j],x,N))) However, for cases where the trap is not taken, my method is about 10 times slower than just doing subst(V,x,N).So your problem boils down to performance. What is your OS and PARI/GP version ? I ask because it seems trap is much slower on your system than on our test systems.
Yeah, it's just a performance issue. My solution works, but 10x slowdown is hard to take. That particular timing number was from 2.3.5-release, on FreeBSD 8.2-RELEASE, Intel i3-550 @ 3.2 GHz. Karim's response about a potential solution in 2.5 may prompt me to update to the latest PARI.