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Russian Peasant Multiplication
15 Commits 1 Branch 0 Tags 69 KiB
Assembly 69.6%
JavaScript 22.8%
BASIC 6.1%
Shell 1.1%
C 0.4%
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Michaelangel007 c2e43a7849 Added explanation
2016-08-19 07:17:35 -07:00
disk Raw Applesoft BASIC disk files 2016-08-18 18:21:06 -07:00
blank_prontodos.dsk Added bootable blank ProntoDOS .dsk 2016-08-18 17:41:35 -07:00
build.sh Added build script 2016-08-18 17:43:21 -07:00
ca65_fixes.inc Assembly ca65 version 2016-08-18 17:42:31 -07:00
README.MD Added explanation 2016-08-19 07:17:35 -07:00
rpm_ca65.s Assembly ca65 version 2016-08-18 17:42:31 -07:00
rpm_m32.s Assembly merlin 32 version 2016-08-18 17:42:48 -07:00
rpm_oop.js Object Orientated Programming Javascript 2016-08-17 14:23:09 -07:00
rpm_proc.js Procedural Javascript - optimize Shr1() 2016-08-18 10:03:46 -07:00
rpm.bas Applesoft BASIC normal and debug versions 2016-08-18 18:20:12 -07:00
rpm.debug.bas Applesoft BASIC normal and debug versions 2016-08-18 18:20:12 -07:00
rpm.dsk Raw Applesoft BASIC disk files 2016-08-18 18:21:06 -07:00

README.MD

Russian Peasant Multiplication

From Assembly to Basic to Javascript.

Here are muy implementations of Russian Peasant Multiplication implemented in various languages:

  • 6502 Assembly Language (Both ca65 and merlin32 sources)
  • Applesoft BASIC
  • JavaScript (Procedural version)
  • JavaScript (OOP version)

A .dsk image has been provided as an convenience.

To see how much faster the Assembly version is then the BASIC version:

RUN  RPM.BAS
BRUN RPM.BIN

And enter in 123456789 * 987654321 respectively for A and B ...

Version Time
Applesoft 33 s
Assembly ~1 s

So what the heck is it?

An alternative algorith to implement multiplication using only:

  • bit-shift (left and right), and
  • addition.

Example of "normal" multiplication:

In base 10:

             86
           x 57
           ----
            602
           430
           ====
           4902

In base 2:

    01010110  (86)
    00111001  (57)
    --------
    01010110  (86 * 2^0 =   86)
   00000000   (86 * 2^1 =  172)
  00000000    (86 * 2^2 =  344)
 01010110     (86 * 2^3 =  688)
01010110      (86 * 2^4 = 1376)

01010110 (86 * 2^5 = 2752)

01001100100110 (4902 = 862^0 + 862^3 + 862^4 + 862^5)

Example of Russian Peasant multiplication:

In Base 10:

               A   B  Sum
              86  57    86
             172  28    86
             344  14    86
             688   7   774
            1376   3  2150
            2752   1  4902

In Base 2:

               A  B         Sum            Sum  = 0
        01010110  00111001  00000001010110 Sum += A
       010101100  00011100  00000001010110 --
      0101011000  00001110  00000001010110 --
     01010110000  00000111  00001100000110 Sum += A
    010101100000  00000011  00100001100110 Sum += A
   0101011000000  00000001  01001100100110 Sum += A