benchmarking

I was curious if we finally get a fast datetime library with JDK8. Nearly all LocalDate computations use toEpochDay so I looked at the source and the large number of divisions and branches made me curious if I could do better. I eliminated some branching and all but one division, however the speedup is worse than expected. So my first question how is it possible that an algorithm using multiple division takes only about 30 cycles (throughput). Holger's comments seem to have answered this: Division by a small constant gets JIT-ed to multiplication. I did it manually and now I'm consistently

Hey there. Today I wrote a small benchmark script to compare performance of copying variables vs. creating references to them. I was expecting, that creating references to large arrays for example would be significantly slower than copying the whole array. Here is my benchmark code: <?php $array = array(); for($i=0; $i<100000; $i++) { $array[] = mt_rand(); } function recursiveCopy($array, $count) { if($count === 1000) return; $foo = $array; recursiveCopy($array, $count+1); } function recursiveReference($array, $count) { if($count === 1000) return; $foo = &$array; recursiveReference($array,

There was a small debate regarding the speed of fnmatch over pathinfo here : how to check if file is php? I wasn't totally convinced so decided to benchmark the two functions. Using dynamic and static paths showed that pathinfo was faster. Is my benchmarking logic and conclusion valid? EDIT : Using mac php from cmd PHP 5.3.0 (cli) (built: Jul 20 2009 13:56:33) Copyright (c) 1997-2009 The PHP Group Zend Engine v2.3.0, Copyright (c) 1998-2009 Zend Technologies dynamic path pathinfo 3.2973630428314 fnmatch 3.4520659446716 x1.05 static path pathinfo 0.86487698554993 fnmatch 1.0420439243317 x1.2

Let's say I have a function that I plan to execute as part of a benchmark. I want to bring this code into the L1 instruction cache prior to executing since I don't want to measure the cost of I$ misses as part of the benchmark. The obvious way to do this is to simply execute the code at least once before the benchmark, hence "warming it up" and bringing it into the L1 instruction cache and possibly the uop cache, etc. What are my alternatives in the case I don't want to execute the code (e.g., because I want the various predictors which key off of instruction addresses to be cold)? One

What is an accurate way to measure the performance of a javascript engine like v8 or spidermonkey ? It should at least have not very high deviations from one evaluation and another, probably allow to rank between different javascript engines on different operating systems and different hardware configurations. My first attempt was this in a web page with nothing on it, I loaded that page in web browsers. Then I tried executing this code in Google Chrome's javascript console and it came out very different as you'll see in the results: mean = function (distr) { var sum = 0; for (obs in distr) {

I created a basic TCP server that reads incoming binary data in protocol buffer format, and writes a binary msg as response. I would like to benchmark the the roundtrip time. I tried iperf, but could not make it send the same input file multiple times. Is there another benchmark tool than can send a binary input file repeatedly? If you have access to a linux or unix machine 1 , you should use tcptrace . All you need to do is loop through your binary traffic test while capturing with wireshark or tcpdump file. After you have that .pcap file 2 , analyze with tcptrace -xtraffic <pcap_filename> 3