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Java Forum / General / February 2007Multiplication with zero
Hi, I'm having a dataset which I use to multiply with another dataset. The number of multiplications is >5000 but constant. The time for computing varies (~0.1-0.2 s) for different datasets, although they are of the same size. What is the reason for this variation? Is it because of the zeros that are in the dataset such that multiplication with zero is faster than any other multiplication. So the more zeros the faster? Or is it maybe a memory problem? Thanks, Peter Vermeer > Hi, > [quoted text clipped - 5 lines] > that multiplication with zero is faster than any other multiplication. > So the more zeros the faster? Or is it maybe a memory problem? There are all sorts of effects that could give a 0.1 second variation in time unless you have things really well locked down. Do repeated runs with the same dataset take the same amount of time? In particular, try alternating runs with a "fast" and a "slow" data set. Patricia > logicl...@yahoo.com wrote: > > Hi, [quoted text clipped - 14 lines] > > Patricia Well the problem is that I have only the results of the different datasets but I'm not able to test these anymore. BTW the total amount of processing time is approx 3.5 sec. Could the things mentioned above be a reason for the time variance? >> logicl...@yahoo.com wrote: >> > Hi, [quoted text clipped - 9 lines] >> There are all sorts of effects that could give a 0.1 second variation in >> time unless you have things really well locked down. [...] > Could the things mentioned above be a reason for the time variance? Yes. - Oliver >> logicl...@yahoo.com wrote: >> > Hi, [quoted text clipped - 20 lines] > datasets but I'm not able to test these anymore. > BTW the total amount of processing time is approx 3.5 sec. If you're trying to significantly speed up that 3.5 seconds, then I'd suggest that attempting to optimize an operation that will, at best, result in a 0.2 second improvement is a less-than-optimal use of your time -- there are undoubtedly other optimizations that could result in greater speed improvement. Cheers GRB > logicl...@yahoo.com wrote innews:1170771926.519649.217370@a34g2000cwb.googlegroups.com: > [quoted text clipped - 31 lines] > Cheers > GRB Actually I don't want to speed it up. I just want to know why these variations exist although the operations are always the same. Thanks, Peter On 7 fév, 11:43, logicl...@yahoo.com wrote: > On 6 Feb., 20:59, "Greg R. Broderick" <gregb > [quoted text clipped - 40 lines] > Thanks, > Peter If you are on windows, the resolution of the timer is about of 10 ms , unless you use the new System.nanoTime(), which resolution is much finer, perhaps it's a problem of resolution of timer (for 0.1 - 0.2 sec, it's probably not the cause). If the program use a database connection to retrieve the dataset, perhaps the network or the database is busy during your test The system is perhaps running another processes which use the CPU in the same time And if your program is multithreaded, other threads perhaps use the CPU So, there is multiple possible cause to explain your problem, we can't tell much better without description of the system (Sorry for my english, it's not my mnative language) Free MagazinesGet these publications absolutely FREE for up to 12 months. There are no hidden fees and no obligation. Simply choose a title, complete the application form and submit it. Read more ...
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