Re: [R] x*x*x*... vs x^n

From: Robin Hankin <>
Date: Thu 30 Jun 2005 - 00:12:36 EST

On Jun 29, 2005, at 02:47 pm, Duncan Murdoch wrote:

> On 6/29/2005 9:31 AM, Robin Hankin wrote:
>> Hi Duncan
>> library(gsl)
>> system.time(ignore <- pow_int(a,8))
>> [1] 1.07 1.11 3.08 0.00 0.00
>> <why the slow execution time?>
> Shouldn't you ask the gsl maintainer that? :-)

well I did ask myself, but in this case the gsl maintainer told me to ask the gsl co-author, who
is no doubt much better informed in these matters ;-)

>> (Of course, I'm not suggesting that other programming tasks be
>> suspended! All I'm pointing
>> out is that there may exist a user to whom fast integer powers are
>> very very important)
> Then that user should submit the patch, not you. But whoever does it
> should include an argument to convince an R core member that the
> change
> is worth looking at, and do it well enough that the patch is accepted.

> Changes to the way R does arithmetic affect everyone, so they had
> better
> be done right, and checking them takes time.

yes, that's a fair point.
But including a native R command, say, wouldn't affect anyone, would it?
One could even use the (tested) GSL code, as it is GPL'ed.

This would just be a new function that users could use at their discretion, and no
existing code would break.

I assume that such a function would not suffer whatever performance disadvantage
that the GSL package approach had, so it may well be quite a significant improvement
over the method used by R_pow_di() in arithmetic.c especially for large n.

best wishes


> Duncan Murdoch
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> mailing list PLEASE do read the posting guide! Received on Thu Jun 30 00:17:40 2005

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