I hazard to say that the author of that blog post isn't using the time
he saved from writing his analyses in C very efficiently. I wonder how
long it took him to write it in C in the first place, even to setup the
testing of C against R, or to write the blog post.
He didn't say.
Jeff
Armstrong, Whit wrote on 01/09/2008 09:49 AM:
> fisher.test seems to use the .C calling convention in a couple of
> different places.
>
> for example:
>
> tmp <- .C("fisher_sim", as.integer(nr), as.integer(nc),
> as.integer(sr), as.integer(sc), as.integer(n),
> as.integer(B), integer(nr * nc), double(n + 1),
> integer(nc), results = double(B), PACKAGE =
> "stats")$results
>
>
> perhaps some R experts on the list can tell us whether there is
> significant overhead to .C vs .Call.
>
> Does .C really duplicate its arguments? What does RObjToCPtr do?
>
>
> (line 1682.. in dotcode.c)
>
> /* Convert the arguments for use in foreign */
> /* function calls. Note that we copy twice */
> /* once here, on the way into the call, and */
> /* once below on the way out. */
> cargs = (void**)R_alloc(nargs, sizeof(void*));
> nargs = 0;
> for(pargs = args ; pargs != R_NilValue; pargs = CDR(pargs)) {
> #ifdef THROW_REGISTRATION_TYPE_ERROR
> if(checkTypes &&
> !comparePrimitiveTypes(checkTypes[nargs], CAR(pargs), dup)) {
> /* We can loop over all the arguments and report all the
>
> erroneous ones, but then we would also want to avoid
>
> the conversions. Also, in the future, we may just
>
> attempt to coerce the value to the appropriate
>
> type. This is why we pass the checkTypes[nargs] value
>
> to RObjToCPtr(). We just have to sort out the ability
>
> to return the correct value which is complicated by
>
> dup, etc. */
> errorcall(call, _("Wrong type for argument %d in call to
> %s"),
> nargs+1, symName);
> }
> #endif
> cargs[nargs] = RObjToCPtr(CAR(pargs), naok, dup, nargs + 1,
> which, symName, argConverters + nargs,
> checkTypes ? checkTypes[nargs] : 0,
> encname);
> #ifdef R_MEMORY_PROFILING
> if (TRACE(CAR(pargs)) && dup)
> memtrace_report(CAR(pargs), cargs[nargs]);
> #endif
> nargs++;
> }
>
> Thanks,
> Whit
>
>
>> -----Original Message-----
>> From: [EMAIL PROTECTED]
>> [mailto:[EMAIL PROTECTED] On Behalf Of Gustaf Rydevik
>> Sent: Wednesday, January 09, 2008 10:25 AM
>> To: r-help@r-project.org
>> Subject: [R] An "R is slow"-article
>>
>> Hi all,
>>
>> Reading the wikipedia page on R, I stumbled across the following:
>> http://fluff.info/blog/arch/00000172.htm
>>
>> It does seem interesting that the C execution is that much
>> slower from R than from a native C program. Could any of the
>> more technically knowledgeable people explain why this is so?
>>
>> The author also have some thought-provoking opinions on R
>> being no-good and that you should write everything in C
>> instead (mainly because R is slow and too good at graphics,
>> encouraging data snooping). See
>> http://fluff.info/blog/arch/00000041.htm
>> While I don't agree (granted, I can't really write C), it
>> was interesting to read something from a very different
>> perspective than I'm used to.
>>
>> Best regards,
>>
>> Gustaf
>>
>> _____
>> Department of Epidemiology,
>> Swedish Institute for Infectious Disease Control work email:
>> gustaf.rydevik at smi dot ki dot se skype:gustaf_rydevik
>>
>> ______________________________________________
>> 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.
>>
>
>
>
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http://biostat.mc.vanderbilt.edu/JeffreyHorner
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