From: helgito@hi.is
Date: Tue 11 Sep 2001 - 23:29:27 EST
Message-id: <3B9E11B7.A9479FE6@hi.is>
>
>
> Why do you think REAL*16 will give you increased accuracy? Accuracy has a
> lot more to do with the algorithms used and their convergence criteria.
> As R is a statistical package, numerical accuracy is almost always
> secondary to data uncertainty.
>
>
I tested a Solaris fotran compiler on a Sun and it allowed REAL*16 whereas
a GNU fortran on the same machine did not. It seems to me that that the
increased
numerical accuracy compared to REAL*8 on an Intel-86 machine was not
proportional. The Intel machines have a numerical stack of lenght 80 so if
the Fortran program is well optimized you should not loose as as many digits
as you might expect.
REAL*8 gives about 15 digits in floating-point. It was my hope that REAL*16
would give around 30. In my simple experiment it seemed that I only got
about 20-25.
Maybe the Sun or the compiler does not use a stack as the Intel-86 machines.
I want to add several hundred thousand numbers, and their squares, which some
are range from maybe 10^(-6) to 1 or more.
With crude programming I fear that I am loosing important digits.
I was wondering whether I should apply for a Sun station or wait further
development.
regards
Helgi
>
> --
-- Helgi Tomasson FAX: 354-552-6806 University of Iceland PHONE:354-525-4571 Faculty of Economics and Business Administration email:helgito@rhi.hi.is Oddi v/ Sturlugotu IS-101 Reykjavik ICELAND-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.- r-help mailing list -- Read http://www.ci.tuwien.ac.at/~hornik/R/R-FAQ.html Send "info", "help", or "[un]subscribe" (in the "body", not the subject !) To: r-help-request@stat.math.ethz.ch _._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._
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