Can anyone give me the approximate time (in nanoseconds) to access L1, L2 and L3 caches, as well as main memory on Intel i7 processors? While this isn’t specifically a programming question, knowing these kinds of speed details is neccessary for some low-latency programming challenges. 5 Answers 5
I am wondering how much of Ulrich Drepper’s What Every Programmer Should Know About Memory from 2007 is still valid. Also I could not find a newer version than 1.0 or an errata. (Also in PDF form on Ulrich Drepper’s own site: https://www.akkadia.org/drepper/cpumemory.pdf) 3 Answers 3
Below are two programs that are almost identical except that I switched the i and j variables around. They both run in different amounts of time. Could someone explain why this happens? Version 1 #include <stdio.h> #include <stdlib.h> main () { int i,j; static int x[4000][4000]; for (i = 0; i < 4000; i++) { … Read more
What is the difference between “cache unfriendly code” and the “cache friendly” code? How can I make sure I write cache-efficient code? 9 s 9 Preliminaries On modern computers, only the lowest level memory structures (the registers) can move data around in single clock cycles. However, registers are very expensive and most computer cores have … Read more
