Ricardo Martinez writes: ricardo, my email client does not know to display your data, but weight is assigned to gws like this: matched_gws[gw_index].weight = t->weight * (rand() >> 8); where t->weight comes from db table. then the gws are sorted based on prefix length, priority and the above weight value. -- juha

Ricardo Martinez writes: ricardo, it is a "feature" of the way randomized weights are currently calculated. if you have two wgs with weights 1 and 2 and then generate two random numbers 1 * random number 2 * random number then the probability that the latter result is less than 10 is 50 %, but that it also is less than the first number is only 25 %. i searched around a bit and didn't find any fast way to calculate a better weighted random number. the algorithms i found where based on an idea of creating an array of gws where each gw appears in the array as many times as its weight is and then a random number is generated between [1, size of the array] and a gw in that random number index of the array is selected. any ideas on how to improve weighted random number calculation without loosing performance? -- juha

Hello Juha. Thanks for your help. The script works fine. We made a test using the values "20 20 20 20 10 10" and it gave us the exact values that I calculated for the actual gateways. Device Calls % GW02 520 1,04 GW03 502 1,01 GW05 12148 24,44 GW06 12276 24,70 GW09 12174 24,49 GW10 12074 24,29 Total 49694 So, we created another "weight" values and gave us the percentage we were looking for. 18 18 18 18 16 16 That gaves us 20% 20% 20% 20% 10% and 10%. So, we think it should be very useful if you can include this script in the "utils", and maybe give more information in the REDME file of LCR about the weight "column", until now we believe this column represents the percentage of each gateway. Thanks again, Regards, Ricardo.- -----Mensaje original----- De: Juha Heinanen [mailto:jh@tutpro.com] Enviado el: domingo, 26 de septiembre de 2010 2:03 Para: Ricardo Martinez; users(a)lists.kamailio.org Asunto: Re: [SR-Users] LCR "weight" column question ricardo, i studied the weight problem a bit more and came to the conclusion that implementing a fair weighting algorithm would be too complicated. below is a script that can be used to find weight values matching desired probabilities for lcr gateways. i don't know if it would be appropriate to include it in utils or scripts directory. -- juha #!/usr/bin/php <?php // This script can be used to find out actual probabilities // that correspond to a list of LCR gateway weights. if ($argc < 2) { echo "Usage: lcr_weight_test.php <list of weights (integers 1-254)>\n"; exit; } $iters = 10000; $rands = array(); for ($i = 1; $i <= $iters; $i++) { $elem = array(); for ($j = 1; $j < $argc; $j++) { $elem["$j"] = $argv[$j] * (rand() >> 8); } $rands[] = $elem; } $sorted = array(); foreach ($rands as $rand) { asort($rand); $sorted[] = $rand; } $counts = array(); for ($j = 1; $j < $argc; $j++) { $counts["$j"] = 0; } foreach ($sorted as $rand) { end($rand); $counts[key($rand)]++; } for ($j = 1; $j < $argc; $j++) { echo "weight " . $argv[$j] . " probability " . $counts["$j"]/$iters . "\n"; } ?>

Daniel-Constantin Mierla writes: daniel, this is the same algorithm that i was looking at to implement only that i was thinking to use an array that was long enough to hold the sum of the weights. in case of lcr, things are more complicated, because in the set of matching gateways for a destination, gws are ordered first based on prefix length, then based on priority and finally based on randomized weight. so there should be several of those arrays. also, the arrays would need to be created and organized every time load_gws() is called, i.e., once per call. this would result in lots of code lines and performance hit at load_gws() call. the script that i wrote can be used to figure out the desired weights without any implementation complexity. just a single rand() call for each matching gw and a single qsort() call for the set is all that is needed. so, for now, i'll include the script in the tools dir and reference it in lcr README. -- juha

Daniel-Constantin Mierla writes: ok, juha

Ovidiu Sas writes: ovidiu, possibly it could be done, but i'm not that good in bash. -- juha

Daniel-Constantin Mierla writes: i created awk version of lcr_weight_test script. i'm not using kamctl myself, but if someone is and would like to call this script from kamctl, he/she should now be able to add that command to kamctl. -- juha

Ovidiu Sas writes: thank you very much, -- juha