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From: eachus@spectre.mitre.org (Robert I. Eachus)
Subject: Re: An interesting quote on Java and C++
Date: 1997/10/03
Message-ID: <EACHUS.97Oct3181234@spectre.mitre.org>#1/1
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References: <5ujjvq$t4s@drn.zippo.com> <EG9rCz.5pH@world.std.com>
 <34160feb.36797713@news.mindspring.com> <dewar.873989964@merv>
 <EGEq96.2H6@world.std.com> <34218E68.63D5@gsg.eds.com> <dewar.874759066@merv>
Organization: The Mitre Corp., Bedford, MA.
Newsgroups: comp.lang.ada
Date: 1997-10-03T00:00:00+00:00
List-Id: <comp.lang.ada>


In article <dewar.874759066@merv> dewar@merv.cs.nyu.edu (Robert Dewar) writes:

 > Of course if you find the non-binary modular stuff useful (I wonder how
 > much it is used outside ACVC tests), then no doubt you regard this as a
 > lucky mistake :-)

   One of the few places where it is useful is in random number
generation, so I was one of the few who felt a need for it.  However,
there is a related "trick" that occaisionally is useful.  Most
hardware architectures support a word * word --> doubleword multiply,
and a corresponding doubleword / word --> word instruction.  Of
course, these are not normally accesable from high-level languages
without implementation dependent techniques. To pick a specific
example, on the SPARC architecture, these instructions can follow one
after the other, but accessing the register holding the high order
bits is otherwise relatively slow.  So,

   type Modular is mod M; --for some non-static binary M.
   X, Y, Z: Modular;
   ...
   X := Y * Z;
   -- can be done in very few clock cycles.

   This is of course most interesting in any application where you are
interested in doing an integer FFT.  Comes up a lot in signal processing.

--

					Robert I. Eachus

with Standard_Disclaimer;
use  Standard_Disclaimer;
function Message (Text: in Clever_Ideas) return Better_Ideas is...