On 23/05/2010, at 5:40 PM, Peter Chubb wrote: >>>>>> "tenzero" == tenzero <[email protected]> writes: > > tenzero> Hi everyone, I'm seeking a preferably citeable reference to > tenzero> the amount of error in the returned result from a Time() > tenzero> command. I want to be able to quote the level of error in > tenzero> timing the execution speed of my project. > > > > Do you mean time(2) ??? Actually I used time(1). This may have been unswise, I'm not certain.
What I am trying to do, is simply determine the execution time of a small app I wrote in Java. Like this: time (java mcoption 104 .05859375 0.001129155 0.09765625 64 4) I am simply trying to record for performance testing, how long my java app takes to execute the Monte Carlo Simulation. I will be using it as a performance baseline to compare against my FPGA implementation. In terms of error, I am simply trying to find out the measurement error in the returned value. eg +- 1 millisecond or whatever. > > Short answer: it depends. > Long answer: time(2) returns the number of seconds since the epoch. > It's accurate for timing in the absence of leap-seconds, and jumps > caused by NTP etc. But it can go backwards, and forwards by more than > one step at a time. > > For details, see time(7). > > > If you want accurate timings, use one of the POSIX monotonic clocks. > man 3 clock_gettime and look for CLOCK_MONOTONIC > > Also, you are aware (I assume) that how long something takes depends > not only on its own processing time, but on how much else is happening > on the system? Yes I accept that I cannot fully control what else is happening across the entire system. Cheers. D. -- SLUG - Sydney Linux User's Group Mailing List - http://slug.org.au/ Subscription info and FAQs: http://slug.org.au/faq/mailinglists.html
