Changes between Version 10 and Version 11 of CreditNew


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Timestamp:
Nov 4, 2009, 3:47:43 PM (14 years ago)
Author:
davea
Comment:

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  • CreditNew

    v10 v11  
    2828
    2929 * Project neutrality: different projects should grant
    30    about the same amount of credit per day for a given host.
     30   about the same amount of credit per day for a given processor.
    3131
    3232It's easy to show that both goals can't be satisfied simultaneously.
     
    241241 * A given sample may be wildly off,
    242242   and we can't let this mess up the average.
     243 * Averages should be weighted by job size.
    243244
    244245In addition, we may as well maintain the variance of the quantities,
    245246although the current system doesn't use it.
    246247
    247 So for each quantity we maintain the following object:
    248 {{{
    249 #define MIN_SAMPLES    20
    250     // after this many samples, use exponentially averaged version
    251 #define SAMPLE_WEIGHT    0.001
    252     // new samples get this weight in exp avg
    253 #define SAMPLE_LIMIT    10
    254     // cap samples at recent_mean*10
    255 
    256 struct STATS {
    257     int nsamples;
    258     double mean;
    259     double sum_var;
    260     double recent_mean;
    261     double recent_var;
    262 
    263     void update(double sample) {
    264         if (sample < 0) return;
    265         if (nsamples > MIN_SAMPLES) {
    266             if (sample > recent_mean*SAMPLE_LIMIT) {
    267                 sample = recent_main*SAMPLE_LIMIT;
    268             }
    269         }
    270         // see http://en.wikipedia.org/wiki/Algorithms_for_calculating_variance
    271         nsamples++;
    272         double delta = sample - mean;
    273         mean += delta/nsamples;
    274         sum_var += delta*(sample-mean);
    275 
    276         if (nsamples < MIN_SAMPLES) {
    277             recent_mean = mean;
    278             recent_var = sum_var/nsamples;
    279         } else {
    280             // update recent averages
    281             delta = sample - recent_mean;
    282             recent_mean += SAMPLE_WEIGHT*delta;
    283             double d2 = delta*delta - recent_var;
    284             recent_var += SAMPLE_WEIGHT*d2;
    285         }
    286     }
    287 };
    288 }}}
     248The code that does all this is
     249[http://boinc.berkeley.edu/trac/browser/trunk/boinc/lib/average.h here].
    289250
    290251== Cross-project scaling factors ==