very quick and basic rule: function call are only expensive if they are called very often (i.e. in inner loops) and if the actual body of the function is very small/cheap. in such cases avoiding function calls by using marco can improve performance. in (most) other cases, function call cost "vanish" behind other costs. Stefan On Fri, Nov 10, 2006 at 07:40:20PM +0100, Martin Kersten wrote:
Wouter Scherphof wrote:
Let me just check if I got this correctly: Is it a general rule that each call to a function generates overhead, that can be eliminated by replacing the function with a macro and "calling" the macro instead?
In general yes, but.... the exploded code may become more difficult to debug (using gdb), the code may become too large for compilers or cache, and you may run out of registers.
But, used with some care you can indeed improve performance significantly.
Regards, Wouter.
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-- | Dr. Stefan Manegold | mailto:Stefan.Manegold@cwi.nl | | CWI, P.O.Box 94079 | http://www.cwi.nl/~manegold/ | | 1090 GB Amsterdam | Tel.: +31 (20) 592-4212 | | The Netherlands | Fax : +31 (20) 592-4312 |