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Re: Reorder some tree codes


Gabriel Dos Reis wrote:
Mark Mitchell <mark@codesourcery.com> writes:

[...]

| This is clearly the kind of change that (if it's an otherwise good
| change) is acceptable in Stage 3; small, but with a non-trivial impact
| on compile-time performance.

I think 0.25% speed up is within the margin of statistical error.

You cannot know that unless you know how Nathan measured, what the variance on his measurements is, etc.


I can state that the way in which we do these measurements typically has a variance in the range of 0.5 seconds over a total run, which takes about 500 seconds. So, the normal variance is about 0.1%, which makes 0.25% significant. This measurement involves building all of Qt (with the usual Qt makefiles) and an associated application, including linking. Therefore, it underestimates the compiler speedup per se, as fixed costs (like linking) exist.

--
Mark Mitchell
CodeSourcery, LLC
mark@codesourcery.com
(916) 791-8304


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