From: Joel VanderWerf <vjoel@...>
Date: 2003-09-23T06:14:33+09:00
Subject: Re: Operator overloading

Johann Hibschman wrote:
> "Robert Klemme" <bob.news@gmx.net> wrote in message news:<bkmq5r$3dhd5$2@ID-52924.news.uni-berlin.de>...
> 
> 
>>You can't.  And you don't need to.  As others pointed out already, Ruby
>>treats all the assignment arithmetic operators as shortcuts and invokes
>>the appropriate operator.  So
> 
> 
> Er.  "You don't need to" is rather extreme.  What about numerical cases?
> 
> i.e., if m is a large matrix, then "m += 1" and "m = m + 1" are rather
> different beasts, since the "obvioius" interpretation of the first involves
> simply incrementing the matrix in place, while the second involves a
> copy.
> 
> Is there a standard work-around for this?  This was one of the reasons I
> stuck with python over ruby, but I've got to admit that I didn't spend a
> huge amount of time researching.

narray has

     self.add! other
     self.sbt! other
     self.mul! other
     self.div! other
     self.mod! other

which presumably are in-place ops. Anyway, they are faster than *= and 
friends:

                             user     system      total        real
warmup                 16.980000   2.850000  19.830000 ( 22.501646)
using *= and /=         0.400000   0.050000   0.450000 (  0.462865)
using mul! and div!     0.160000   0.020000   0.180000 (  0.181544)
using no ops            0.000000   0.000000   0.000000 (  0.006473)

(on PIII850).

=================================
require 'narray'
require 'benchmark'

Benchmark.bm(22) do |test|

   reps = 10_000

   m = NMatrix.float(100,100).fill(1)

   test.report("warmup") do
     (1..reps).each do |i|
       m *= i
       m /= i
     end
   end

   m = NMatrix.float(3,3).fill(1)

   test.report("using *= and /=") do
     (1..reps).each do |i|
       m *= i
       m /= i
     end
   end

   m = NMatrix.float(3,3).fill(1)

   test.report("using mul! and div!") do
     (1..reps).each do |i|
       m.mul! i
       m.div! i
     end
   end

   m = NMatrix.float(3,3).fill(1)

   test.report("using no ops") do
     (1..reps).each do |i|
     end
   end

end