From: robin.vowels@gmail.com
Subject: Re: getting same output as gfortran, long_float
Date: Sun, 3 May 2015 17:42:49 -0700 (PDT)
Date: 2015-05-03T17:42:49-07:00 [thread overview]
Message-ID: <e097d738-5636-40f7-87f9-742a3b6d30c7@googlegroups.com> (raw)
In-Reply-To: <mhujuf$jbs$1@speranza.aioe.org>
On Friday, May 1, 2015 at 11:12:51 AM UTC+10, Nasser M. Abbasi wrote:
> On 4/30/2015 5:08 PM, Dmitry A. Kazakov wrote:
>
> > If GNAT allowed floating-point emulation, you could declare a custom type
> > of required precision:
> >
> > type My_Float is digits 34; -- 112 * lg(2)
> >
> > Which is advisable anyway in order to make your program portable. Using
> > built-in types is a bad idea and poor taste in most cases.
> >
> > Since GNAT does support emulation, at least not with the standard compiler
> > switches, you need a library for doing this.
> >
>
> I found that gfortran can do 128 bit floating point without
> the use of the compiler switch -fdefault-real-8. Which will
> map to similar thing as the above Ada construct:
>
> -------------------
> PROGRAM foo
> IMPLICIT NONE
> REAL(KIND = 16) :: x !-- kind=16 tells it is double quad
No it doesn't. That form is non-standard, and won't compile with some
compilers.
You need to use SELECTED_REAL_KIND or something equivalent.
> x = 12.0D0 * 0.0001D0/(1.0D0 * (1.0D0 - 0.1D0)**4 )
And the above constants are double precision, not quadruple precision,
to the numerical result with have no more precision than double.
> PRINT *, x
> END PROGRAM
> ------------------
>
> gfortran -Wall foo2.f90
> ./a.out
> 1.82898948331047112025871115292829927E-0003
next prev parent reply other threads:[~2015-05-04 0:42 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-04-30 21:17 getting same output as gfortran, long_float Nasser M. Abbasi
2015-04-30 22:08 ` Dmitry A. Kazakov
2015-04-30 22:11 ` Dmitry A. Kazakov
2015-04-30 22:37 ` Nasser M. Abbasi
2015-04-30 22:53 ` Nasser M. Abbasi
2015-05-01 7:22 ` Jacob Sparre Andersen
2015-05-01 1:12 ` Nasser M. Abbasi
2015-05-01 6:52 ` Dmitry A. Kazakov
2015-05-01 7:32 ` Nasser M. Abbasi
2015-05-01 7:45 ` Dmitry A. Kazakov
2015-05-04 0:15 ` robin.vowels
2015-05-04 7:21 ` Dmitry A. Kazakov
2015-05-04 8:53 ` robin.vowels
2015-05-04 10:18 ` Dmitry A. Kazakov
2015-05-04 13:45 ` robin.vowels
2015-05-04 14:47 ` Dmitry A. Kazakov
2015-05-07 2:01 ` robin.vowels
2015-05-01 23:24 ` Dennis Lee Bieber
2015-05-04 0:09 ` robin.vowels
2015-05-01 7:01 ` Dmitry A. Kazakov
2015-05-04 0:42 ` robin.vowels [this message]
2015-04-30 22:12 ` Jeffrey R. Carter
2015-04-30 22:27 ` Qun-Ying
2015-05-01 0:59 ` Dennis Lee Bieber
2015-04-30 22:32 ` Nasser M. Abbasi
2015-05-01 1:16 ` Jeffrey R. Carter
2015-05-01 1:40 ` Nasser M. Abbasi
2015-05-01 7:47 ` Jacob Sparre Andersen
2015-05-01 15:39 ` Waldek Hebisch
2015-05-01 17:27 ` Nasser M. Abbasi
2015-05-01 18:03 ` Nasser M. Abbasi
2015-05-04 0:51 ` robin.vowels
2015-05-04 0:47 ` robin.vowels
2015-05-01 8:21 ` Simon Wright
2015-05-01 11:55 ` Georg Bauhaus
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