performance
One could use a profiler, but why not just halt the program? [closed]
On Java servers it’s always been a neat trick to do 2-3 quick Ctrl–Breakss in a row and get 2-3 threaddumps of all running threads. Simply looking at where all the threads “are” may extremely quickly pinpoint where your performance problems are. This technique can reveal more performance problems in 2 minutes than any other … Read more
Why is MATLAB so fast in matrix multiplication?
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
Speed up the loop operation in R
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
How to find the kth largest element in an unsorted array of length n in O(n)?
How to find the kth largest element in an unsorted array of length n in O(n)?
Why are loops always compiled into “do…while” style (tail jump)?
Related: asm loop basics: While, Do While, For loops in Assembly Language (emu8086) Fewer instructions / uops inside the loop = better. Structuring the code outside the loop to achieve this is very often a good idea. Sometimes this requires “loop rotation” (peeling part of the first iteration so the actual loop body has the … Read more
How can I determine whether a 2D Point is within a Polygon?
How can I determine whether a 2D Point is within a Polygon?