Article View: comp.lang.fortran
Article #6533Re: Precision of floating point multiply
From: Glen Herrmannsfeldt
Date: Mon, 29 Sep 2003 14:36
Date: Mon, 29 Sep 2003 14:36
36 lines
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2682 bytes
"Nick Maclaren" <nmm1@cus.cam.ac.uk> wrote in message news:bl8q1g$iv7$1@pegasus.csx.cam.ac.uk... > > In article <kmRdb.626671$YN5.452649@sccrnsc01>, > "Glen Herrmannsfeldt" <gah@ugcs.caltech.edu> writes: > |> > |> Since my post on Fortran G and H, I have also run the same test on PL/I (F). > |> That might be the compiler you used. > |> > |> For C=C+A*B; single precision A and B, and double precision C, it does the > |> same thing Fortran did. > |> > |> It would be interesting to see the results from newer Fortran and PL/I > |> compilers. > > Yes, but you haven't posted WHAT it did! Given that it doesn't need > to do anything special, I am puzzled over what instructions it inserts. > Can you post the generated code? I thought it was somewhere in the thread, but maybe not. For C=C+A*B, single precision A, B, and double precision C: LE 0,A load single precision A ME 0,B Multiply by B generating double product in float register 0 SDR 2,2 Clear double float register 2 LER 2,0 copy single value from reg 0 to reg 2 AD 2,C add double C STD 2,C store double into C The SDR and LER are used to clear the low half of the product. -- glen
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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: 1094ba,7830916812112af0 X-Google-Attributes: gid1094ba,public X-Google-Thread: 102b75,7830916812112af0 X-Google-Attributes: gid102b75,public X-Google-ArrivalTime: 2003-09-29 07:36:14 PST Path: arc1-ca.pugleaf.net!news1.google.com!newsfeed.stanford.edu!headwall.stanford.edu!newshub.sdsu.edu!elnk-nf2-pas!newsfeed.earthlink.net!wn14feed!worldnet.att.net!204.127.198.203!attbi_feed3!attbi.com!sccrnsc03.POSTED!not-for-mail From: "Glen Herrmannsfeldt" <gah@ugcs.caltech.edu> Newsgroups: comp.lang.fortran,comp.arch,bit.listserv.ibm-main,alt.folklore.computers References: <dG4db.598668$uu5.97984@sccrnsc04> <iu6fnvch0g09q9f335tt89ogfcj5jm2ovh@4ax.com> <kmRdb.626671$YN5.452649@sccrnsc01> <bl8q1g$iv7$1@pegasus.csx.cam.ac.uk> Subject: Re: Precision of floating point multiply Lines: 40 X-Priority: 3 X-MSMail-Priority: Normal X-Newsreader: Microsoft Outlook Express 5.00.2919.6700 X-MimeOLE: Produced By Microsoft MimeOLE V5.00.2919.6700 Message-ID: <xrXdb.631209$Ho3.121609@sccrnsc03> NNTP-Posting-Host: 12.207.204.17 X-Complaints-To: abuse@comcast.net X-Trace: sccrnsc03 1064846173 12.207.204.17 (Mon, 29 Sep 2003 14:36:13 GMT) NNTP-Posting-Date: Mon, 29 Sep 2003 14:36:13 GMT Organization: Comcast Online Date: Mon, 29 Sep 2003 14:36:13 GMT