Q36901: Numerical Calculations and Loops Are Faster with Integers

Article: Q36901
Product(s): See article
Version(s): 4.00 4.00b 4.50
Operating System(s): MS-DOS
Keyword(s): ENDUSER | B_BasicCom floating point | mspl13_basic
Last Modified: 28-DEC-1989

The time needed to process numbers as floating-point numbers is
significantly longer than with integers. Since the default data type
is single-precision floating-point numbers, it is quite common for
people to use a floating-point variable to represent a number that
could be represented as an integer or long. A FOR-NEXT loop that does
nothing takes approximately six times as long to run when the index
variable is specified as a single-precision number rather than as an
integer.

This information applies to Microsoft QuickBASIC Versions 4.00, 4.00b,
and 4.50, to Microsoft BASIC Compiler Versions 6.00 and 6.00b for
MS-DOS and MS OS/2, and to Microsoft BASIC PDS Version 7.00 for MS-DOS
and MS OS/2.

In the following code example that multiplies zero by zero, the
version that uses integer variables runs five times as fast as the
version using floating-point variables if the computer has an 80x87
coprocessor or 25 times as fast with no coprocessor.

The results of testing with a previous version of QuickBASIC is as
follows:

The integer loop is only three times as fast under QuickBASIC Version
3.00.

The following is a code example:

' The following loop uses the default data type, single precision:
CLS
x1 = TIMER
FOR i = 1 TO 30000
  j = j * j
NEXT i
x2 = TIMER
' The following loop uses integer variables:
DEFINT I-K
FOR ii = 1 TO 30000
   k = k * k
NEXT
x3 = TIMER
PRINT "default loop ="; x2 - x1
PRINT "integer loop  ="; x3 - x2

THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY.

Copyright Microsoft Corporation 1986-2002.