If you want a more accurate measurement than the answer above: set statistics time on — Query 1 goes here — Query 2 goes here set statistics time off The results will be in the Messages window. Update (2015-07-29): By popular request, I have written a code snippet that you can use to time an … Read more
-ffast-math does a lot more than just break strict IEEE compliance. First of all, of course, it does break strict IEEE compliance, allowing e.g. the reordering of instructions to something which is mathematically the same (ideally) but not exactly the same in floating point. Second, it disables setting errno after single-instruction math functions, which means … Read more
This kind of question is recurring and should be answered more clearly than “MATLAB uses highly optimized libraries” or “MATLAB uses the MKL” for once on Stack Overflow. History: Matrix multiplication (together with Matrix-vector, vector-vector multiplication and many of the matrix decompositions) is (are) the most important problems in linear algebra. Engineers have been solving … Read more
I’m currently running Android Studio on Windows 8.1 machine with 6 gigs of RAM. I found that disabling VCS in android studio and using an external program to handle VCS helped a lot. You can disable VCS by going to File->Settings->Plugins and disable the following: CVS Integration Git Integration GitHub Google Cloud Testing Google Cloud … Read more
GHC Core is the System FC language into which all Haskell is translated. The (approximate) grammar for Core is given by: Core is closely related to the simpler and better known System F. All transformations GHC does on the Core level are type-preserving refactorings of this Core representation, to improve performance. And, not so well … Read more
Biggest problem and root of ineffectiveness is indexing data.frame, I mean all this lines where you use temp[,]. Try to avoid this as much as possible. I took your function, change indexing and here version_A dayloop2_A <- function(temp){ res <- numeric(nrow(temp)) for (i in 1:nrow(temp)){ res[i] <- i if (i > 1) { if ((temp[i,6] … Read more
Numbers everyone should know 0.5 ns – CPU L1 dCACHE reference 1 ns – speed-of-light (a photon) travel a 1 ft (30.5cm) distance 5 ns – CPU L1 iCACHE Branch mispredict 7 ns – CPU L2 CACHE reference 71 ns – CPU cross-QPI/NUMA best case on XEON E5-46* 100 ns – MUTEX lock/unlock 100 ns … Read more
Starting with Chrome 38 you can do this without any plugins. Just click inspect element (or F12 hotkey), then click on “toggle device mod” and you will see something like this: Among many other features it allows you to simulate specific internet connection (3G, GPRS) P.S. for people who try to limit the upload speed. … Read more
You can use this: SELECT COUNT(*) FROM (SELECT DISTINCT column_name FROM table_name) AS temp; This is much faster than: COUNT(DISTINCT column_name)
This is called finding the k-th order statistic. There’s a very simple randomized algorithm (called quickselect) taking O(n) average time, O(n^2) worst case time, and a pretty complicated non-randomized algorithm (called introselect) taking O(n) worst case time. There’s some info on Wikipedia, but it’s not very good. Everything you need is in these powerpoint slides. … Read more