Re: Precision of floating point multiply

Article View: comp.lang.fortran

Article #6534

#6534

From: Nick Maclaren
Date: Tue, 30 Sep 2003 07:46

24 lines
2306 bytes

In article <TD0eb.630592$YN5.454239@sccrnsc01>,
"Glen Herrmannsfeldt" <gah@ugcs.caltech.edu> writes:
|> 
|> Unnormalized values are also allowed in mathematical operations.  For
|> addition and subtraction, the prenormalization (aligning the hexadecimal
|> point) is done based on the exponent supplied.  The Fortran AINT function
|> consists of adding 0*16**7, and DINT of adding 0*16**15.  Prenormalization
|> will shift out fractional digits, zero will be added, and post normalization
|> will shift it back to properly normalized form.

That was model dependent.  If I recall, neither IBM's nor Hitachi's
vector units accepted unnormalised operands.

|> Multipy, divide, and square root prenormalize the the operand if it isn't
|> normalized.  (This is from ESA/390.)

That was model dependent, too, if I recall _ I think that multiply
and divide were prone to not prenormalising, at least on some of
the System/360 systems.


Regards,
Nick Maclaren.

Technical Details

Message-ID: <blbcdh$lob$1@pegasus.csx.cam.ac.uk>

Path:

arc1-ca.pugleaf.net!archiver1.google.com!news2.google.com!newsfeed.stanford.edu!nntp.cs.ubc.ca!fu-berlin.de!server1.netnews.ja.net!pegasus.csx.cam.ac.uk!nmm1

References:

<dG4db.598668$uu5.97984@sccrnsc04> <iu6fnvch0g09q9f335tt89ogfcj5jm2ovh@4ax.com> <kmRdb.626671$YN5.452649@sccrnsc01> <bl8q1g$iv7$1@pegasus.csx.cam.ac.uk> <xrXdb.631209$Ho3.121609@sccrnsc03> <ron-shepard-609A55.10533829092003@news.comcast.giganews.com> <uefziffu7c.fsf@altair.dfrc.nasa.gov> <vngokjk8nourca@corp.supernews.com> <TD0eb.630592$YN5.454239@sccrnsc01>

Show Full Headers

Complete Article Headers

X-Google-Language: ENGLISH,ASCII-7-bit
X-Google-Thread: fd4af,7830916812112af0
X-Google-Attributes: gidfd4af,public
X-Google-Thread: fd705,7830916812112af0
X-Google-Attributes: gidfd705,public
X-Google-Thread: 102b75,7830916812112af0
X-Google-Attributes: gid102b75,public
X-Google-Thread: 1094ba,7830916812112af0
X-Google-Attributes: gid1094ba,public
X-Google-ArrivalTime: 2003-09-30 00:47:00 PST
Path: arc1-ca.pugleaf.net!archiver1.google.com!news2.google.com!newsfeed.stanford.edu!nntp.cs.ubc.ca!fu-berlin.de!server1.netnews.ja.net!pegasus.csx.cam.ac.uk!nmm1
From: nmm1@cus.cam.ac.uk (Nick Maclaren)
Newsgroups: comp.lang.fortran,comp.arch,bit.listserv.ibm-main,alt.folklore.computers
Subject: Re: Precision of floating point multiply
Date: 30 Sep 2003 07:46:57 GMT
Organization: University of Cambridge, England
Lines: 24
Message-ID: <blbcdh$lob$1@pegasus.csx.cam.ac.uk>
References: <dG4db.598668$uu5.97984@sccrnsc04> <iu6fnvch0g09q9f335tt89ogfcj5jm2ovh@4ax.com> <kmRdb.626671$YN5.452649@sccrnsc01> <bl8q1g$iv7$1@pegasus.csx.cam.ac.uk> <xrXdb.631209$Ho3.121609@sccrnsc03> <ron-shepard-609A55.10533829092003@news.comcast.giganews.com> <uefziffu7c.fsf@altair.dfrc.nasa.gov> <vngokjk8nourca@corp.supernews.com> <TD0eb.630592$YN5.454239@sccrnsc01>
NNTP-Posting-Host: virgo.cus.cam.ac.uk
Originator: nmm1@virgo.cus.cam.ac.uk

Reply to Parent Message