From: nahaj@u.cc.utah.edu (John Halleck)
Subject: Re: Looking for Ada Technique Name and References
Date: 2000/02/22
Date: 2000-02-22T03:21:36+00:00 [thread overview]
Message-ID: <88svc0$nkj$1@coward.ks.cc.utah.edu> (raw)
In-Reply-To: 88s90i$8mi$1@ns3.arlut.utexas.edu
Diana Webster (dkweb@arlut.utexas.edu) wrote:
: This technique is called "composition" in mathematics, i.e., the composition
: of two functions,
: i.e, sum (average (xnum)). Most programming languages support this.
The trick posted is not a composition of functions.
It keeps the notation of the composition of functions, but substitutes
a special purpose routine faster than the composition of functions.
This trick is *** NOT *** supported by most languages.
: John Halleck <nahaj@u.cc.utah.edu> wrote in message
: news:88kh6q$j4j$1@coward.ks.cc.utah.edu...
: > > John Halleck (nahaj@u.cc.utah.edu) wrote:
: > > : I would appreciate it if someone could give me the name and a
: > > : print reference for the following technique.
: >
: > > Someone Replied:
: >
: > > It is called overloading.
: >
: > It uses overloading, but that was not the technique I was trying
: > to get accross.
: >
: > The technique in question is turning the what is normally written
: > as two function calls (More or less:)
: > "*" (Transpose (A), B)
: > into a type mark and a single function call to a special function
: > that can handle it all more effeciently.
: >
: > >
: > > : Background:
: > >
: > > : Many matrix methods are written in the form A := Transpose(B)*C
: > > : But, actually forming the transpose is expensive, and you are
: better
: > > : off just writing a second matrix multiply routine that takes the
: > > : two matrices and treats the one as a transpose without actually
: > > : doing the transpose.
: > >
: > > : Below is a technique that allows one to write it as one normally
: > > : sees it written, but lets the Ada compiler do the selection of
: > > : an appropriate routine.
: > >
: > > : Is there a name for this technique? Does it appear already
: documented
: > > : somewhere?
: > >
: > >
: : --------------------------------------------------------------------------
: ----
: > >
: > > : -- ...
: > >
: > > : type Matrix is array (positive range <>, positive range <>) of Float;
: > > : type Transpose is new Matrix;
: > >
: > > : -- ...
: > >
: > > : -- This is just a matrix multiply routine.
: > > : function "*" (Left : Matrix; Right : Matrix) return Matrix;
: > >
: > > : -- This routine multiplies the transpose of Left by Right.
: > > : function "*" (Left : Transpose; Right : Matrix) return Matrix;
: > >
: > > : ----------
: > >
: > > : -- Examples:
: > > : A, B, C, D, E: Matrix;
: > >
: > > : -- ...
: > >
: > > : A := B * C; -- Matrix multiply.
: > > : D := Transpose (E) * F; -- D gets the result of multiplying E'F
: > > : -- (By selecting the appropriate routine.
: > >
: > > : ---------------------------------------------------------------------
next prev parent reply other threads:[~2000-02-22 0:00 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <88kegp$iso$1@coward.ks.cc.utah.edu>
[not found] ` <88kh6q$j4j$1@coward.ks.cc.utah.edu>
2000-02-18 0:00 ` Looking for Ada Technique Name and References Tucker Taft
2000-02-21 0:00 ` Diana Webster
2000-02-22 0:00 ` John Halleck [this message]
2000-02-22 0:00 ` tmoran
2000-02-22 0:00 ` David Starner
2000-02-23 0:00 ` tmoran
2000-02-22 0:00 ` Vladimir Olensky
2000-02-22 0:00 ` John Halleck
2000-02-23 0:00 ` Nick Roberts
2000-02-22 0:00 ` Jon S Anthony
2000-02-28 0:00 ` Charles D. Hixson
2000-02-28 0:00 ` Jon S Anthony
2000-02-29 0:00 ` Charles Hixson
2000-02-29 0:00 ` Brian Rogoff
2000-02-29 0:00 ` Jon S Anthony
2000-02-29 0:00 ` Brian Rogoff
2000-02-29 0:00 ` Jon S Anthony
2000-03-01 0:00 ` Charles Hixson
2000-03-01 0:00 ` Brian Rogoff
2000-03-01 0:00 ` Jon S Anthony
2000-03-04 0:00 ` Nick Roberts
2000-02-29 0:00 ` Wes Groleau
2000-02-29 0:00 ` Gautier
2000-03-01 0:00 ` Wes Groleau
2000-02-22 0:00 ` Gautier
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