Rational Developer for System z
PL/I for Windows, Version 8.0, Programming Guide

Improving performance

Selecting compile-time options for optimal performance
OPTIMIZE
IMPRECISE
GONUMBER
SNAP
RULES
PREFIX
CONVERSION
FIXEDOVERFLOW
DEFAULT
BYADDR or BYVALUE
(NON)CONNECTED
RETURNS(BYVALUE) or RETURNS(BYADDR)
(NO)DESCRIPTOR
(RE)ORDER
LINKAGE
ASCII or EBCDIC
IEEE or HEXADEC
(NON)NATIVE
(NO)INLINE
Summary of compile-time options that improve performance
Coding for better performance
DATA-directed input and output
Input-only parameters
String assignments
Loop control variables
PACKAGEs versus nested PROCEDUREs
Example with nested procedures
REDUCIBLE functions
DEFINED versus UNION
Named constants versus static variables
Example with optimal code but no meaningful names
Avoiding calls to library routines

Many considerations for improving the speed of your program are independent of the compiler that you use and the platform on which it runs. This chapter, however, identifies those considerations that are unique to the workstation PL/I compiler and the code it generates.


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