On Sat, 7 Jul 2007, Andrey Chernov wrote: > On Sat, Jul 07, 2007 at 01:51:11PM -0500, Sean C. Farley wrote: >> I agree that it would be faster for a subset of an existing environ. >> On the other hand, in the case of emptying the environment, my method >> would be faster since no deallocation, allocation nor setenv() calls >> would be called assuming putenv() was not used. I could try a few >> tests to see what is faster in which case, but I do not think environ >> changes happen often enough to make speed a factor. > > Well, lets go with that. I ran the tests out of curiosity. All code is here[1]. The dropping was effectively freeing envVars and the environ that getenv.c creates for the program. All other counters were set to zero. The first test (timing-clear.c) cleared the environment by swapping two char ** arrays containing a single NULL pointer. 500000 iterations. x drop/clear-timings.txt + keep/clear-timings.txt N Min Max Median Avg Stddev x 50 1.634899 1.672082 1.656838 1.6567984 0.0093033009 + 50 1.326203 1.348855 1.3296575 1.3323876 0.0062632107 Difference at 95.0% confidence -0.324411 +/- 0.00314674 -19.5806% +/- 0.189929% (Student's t, pooled s = 0.0079303) The second test (timing-merge.c) swapped two duplicates of my environment over 5000 iterations. x drop/merge-timings.txt + keep/merge-timings.txt N Min Max Median Avg Stddev x 50 1.337052 1.406142 1.3663635 1.3634524 0.015210835 + 50 0.889559 0.913354 0.8943785 0.89644634 0.0056274351 Difference at 95.0% confidence -0.467006 +/- 0.00455057 -34.2517% +/- 0.333753% (Student's t, pooled s = 0.0114682) Surprisingly, keeping the pointers saved time even if calling setenv(). Sean 1. http://www.farley.org/freebsd/tmp/setenv/clearenv/ -- scf_at_FreeBSD.orgReceived on Sun Jul 08 2007 - 00:04:17 UTC
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