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posted by LaminatorX on Sunday March 16 2014, @03:28AM   Printer-friendly
from the premature-optimization-is-the-root-of-all-evil dept.

Subsentient writes:

"I've been writing C for quite some time, but I never followed good conventions I'm afraid, and I never payed much attention to the optimization tricks of the higher C programmers. Sure, I use const when I can, I use the pointer methods for manual string copying, I even use register for all the good that does with modern compilers, but now, I'm trying to write a C-string handling library for personal use, but I need speed, and I really don't want to use inline ASM. So, I am wondering, what would other Soylenters do to write efficient, pure, standards-compliant C?"

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  • (Score: 4, Insightful) by maxwell demon on Sunday March 16 2014, @08:45PM

    by maxwell demon (1608) on Sunday March 16 2014, @08:45PM (#17269) Journal

    However today neither counting instruction, nor adding cycles is going to give a good estimate about your running time (unless it turns out e.g. that the loop is slightly too large to fit into the instruction cache), because the processors tend to do a lot behind the scenes (register renaming, branch prediction, out-of-order execution, speculative execution, ...). Far more important issues are things like cache locality (this alone can get you quite a bit of speedup, and can be analyzed entirely on the C level). And of course no amount of micro-optimization can save you from a badly chosen algorithm.

    The Tao of math: The numbers you can count are not the real numbers.
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