From 20e3b69938ba04116a09e98baa8d9fbe18c382f5 Mon Sep 17 00:00:00 2001 From: Richard Kreckel Date: Sun, 12 Oct 2003 14:18:49 +0000 Subject: [PATCH] * times.cpp (randomify_symbol_serials): New. --- check/times.cpp | 27 +++++++++++++++++++++++++++ 1 file changed, 27 insertions(+) diff --git a/check/times.cpp b/check/times.cpp index 9ada2bf6..ce5730b9 100644 --- a/check/times.cpp +++ b/check/times.cpp @@ -23,8 +23,35 @@ #include #include "times.h" +/** Generate a random amount of symbols and destroy them again immediatly. + * This operation effectively makes the serial numbers of all subsequent + * symbols unpredictable. If the serials are unpredictable, then so are + * their hash values. If the hash values are unpredictable, then so are + * the canonical orderings. If the canonical orderings are unpredictable, + * all subsequent times are subject to some variation. This variation, + * however is natural and desireable for two reasons: First, we cannot know + * how many symbols have been generated before in real world computations. + * Second, the following timings are subject to some semi-random variation + * anyways because short timings need to be repeated until enough time has + * gone by for the measurement to be reliable. During this process the serial + * numbers will be shifted anyways in a semi-random way. It is better not + * to lull the user in a false sense of reproducibility and instead confront + * her with the normal variation to be expected. + */ +void randomify_symbol_serials() +{ + srand((unsigned)time(NULL)); + const int m = rand() % 666; + for (int s=0; s