Version 1 of Speed issues

This page is intended to document issues when effective execution of Tcl scripts is targeted. Please add any single topic below as to keep it as a comprehensive list. Append general comments as usual to the end of this page -- RJM.

Write expr commands with the argument in curly braces whenever possible. This avoids conversion of numbers in strings and back. The speed impact may be a factor of 20 or so.
Do not write procs without Arguments. Empty procs may execute approx. 4 times slower. At least speed critical procs schould be defined with a dummy argument.

RJM: Referencing to (2) I can say that I found this by accident. On a Win98 machine with 266 MHz clock, the following execution times apply:

An empty proc without Arguments:

 % proc test {} {}
 % time {test} 1000
 95 microseconds per iteration

An empty proc with an Argument:

 % proc fast {x} {}
 % time {fast 5} 1000
 12 microseconds per iteration

I performed several variations, also with filled body and so on. The crucial differencs lies in defining a proc with or without an argument.

MSW: Actually calling a proc without an argument. For comparison:

 % time {test} 1000
 12 microseconds per iteration
 % time {fast 5} 1000
 3 microseconds per iteration
 % proc maybe {{empty {}}} {}
 % time {maybe} 1000
 13 microseconds per iteration
 % time {maybe empty} 1000
 3 microseconds per iteration