---------- Forwarded message ----------
From: Antonio Paredes <antonioparedes14@gmail.com>
Date: Tue, Oct 6, 2009 at 9:41 AM
Subject: Re: [R] Long for Loop- calling C from R - Parallel Computing
To: Karl Ove Hufthammer <karl@huftis.org>


Hello again,

I'm hoping to get a response from some of the R gurus in this list. Is my
assumption that R is not designed or build to deal with high levels (a lots
of simulated data) simulation correct. For example, how to minimize system
time; do one have to call a lower level language like C or Fortran; or just,
like many of you have done,  do a lots of programing in R and eventually the
tricks will be learned.

Thanks

On Mon, Oct 5, 2009 at 8:35 AM, Antonio Paredes
<antonioparedes14@gmail.com>wrote:

> In my case it does, because I need to preserved a "high level" of
> independence (lack of correlation) among the different groups of 60. Also,
> when I say final result I mean computation of standard errors and that
> source of stuff; sorry about the lack clarity in my statement.
>
>
> On Mon, Oct 5, 2009 at 9:48 AM, Karl Ove Hufthammer <karl@huftis.org>wrote:
>
>> In article <6f6f0fd60910050629p28c99209jcd7836353fd2d754
>> @mail.gmail.com>, antonioparedes14@gmail.com says...
>> > I'm running the following for loop to generate random variables in
>> chunks of
>> > 60 at a time (l), here h is of order in millions (could be 5 to 6
>> millions),
>> > note that generating all the variables at once could have an impact on
>> the
>> > final results
>>
>> No, it will not. See this example code for an illustration:
>>
>> set.seed(1)
>> rnorm(3)
>> rnorm(3)
>> set.seed(1)
>> rnorm(6)
>>
>> So if you generate the six numbers three at a time or all at once gives
>> exactly the same result.
>>
>> So my suggestion is to generate all the numbers at once. That takes next
>> to no time. Or, if it takes too much memory, generate for example a
>> million at once, and repeat a few times.
>>
>> --
>> Karl Ove Hufthammer
>>
>> ______________________________________________
>> R-help@r-project.org mailing list
>> https://stat.ethz.ch/mailman/listinfo/r-help
>> PLEASE do read the posting guide
>> http://www.R-project.org/posting-guide.html
>> and provide commented, minimal, self-contained, reproducible code.
>>
>
>
>
> --
> -Tony
>



-- 
-Tony



-- 
-Tony

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