Numerical Calculations and Loops Are Faster with Integers (36901)

SUMMARY

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.

MORE INFORMATION

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