Re: Rounding off double precision


In your case, use of the F90 Floor function thus:

double precision :: x
x= COS(90 * 3.141592653589793238d0 / 180.)
! round(x) = foor(x+0.5D0)
write(*,*) floor(x+0.5D0)
end

when compiled and run will write 0.0

For Fortran 77 define Floor as:
DINT(X)=X-DMOD(X,1.D0)
FLOOR(X)=DINT(X)-DMOD(2.D0+DSIGN(1.D0,X),3.D0)

For borderline cases of rounding to the nearest whole number one
can use a Fortran rendition of the APL toleranat (that is, fuzzy))
Floor (and Round functions:

http://ftp.aset.psu.edu/pub/ger/fortran/hdk/eps.f90
(this includes a sample main program).

Skip Knoble


On Fri, 28 Mar 2008 20:43:53 -0700 (PDT), Bamm <bammster@xxxxxxxxx> wrote:

-|I'm trying some calculations in double precision, and I'd like the
-|output rounded off so that errors in calculation are not shown. For
-|instance, the result of COS(90 * 3.141592653589793238d0 / 180.) is
-|-4.37113886E-06. I'd like it to be zero. Thanks for any help.

.

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