sqrt

As it currently stands, this question is not a good fit for our Q&A format. We expect answers to be supported by facts, references, or expertise, but this question will likely solicit debate, arguments, polling, or extended discussion. If you feel that this question can be improved and possibly reopened, visit the help center for guidance. Closed 7 years ago . Implement double sqrt(double x) in C++ without using std library. This is a facebook interview question I saw here. http://www.glassdoor.com/Interview/Implement-double-sqrt-double-x-in-C-QTN_87210.htm Any other good idea about this?... !

This compiles fine #include <math.h> int main(void) { double i = sqrt(9.0); } If I change 9.0 to -9.0, then my compiler (GNU C) gives an error about an undefined reference to 'sqrt'. I was expecting the sqrt function to return NaN or an exception. How does the C library only define sqrt for non-negative arguments? This is happening because gcc can use builtin functions during the optimization process to compute certain functions including sqrt at compile time in many but not all cases. If that is the case it will not need to emit a call to sqrt and therefore will not need to link against libm

I practice for an exam in Java. One of the questions I faced today is: Given an array with n numbers, I need to check if there are 2 subarrays(doesn't have to be equal) that their multiplication equals - if there are, will return true, else false. for example : if the array is : {2,15,3,4,2,5} - will return True if the array is : {2,4,6,2,3,4} - will return False. the answer must be recursive, without any loops. so I thought that if there are 2 sub arrays that their multiplication equal it means that the total multiplication of the whole array must be a square root number. for example at the

What is the difference between x**(1/2) , math.sqrt() and cmath.sqrt() ? Why does cmath.sqrt() get complex roots of a quadratic right alone? Should I use that for my square roots exclusively? What do they do in the background differently? If you look at the documentation for cmath and math respectively, you will find that: cmath "provides access to mathematical functions for complex numbers" math "functions cannot be used with complex numbers; use the functions of the same name from the cmath module if you require support for complex numbers." The (**) operator maps to the pow function, with

Consider the following code: #include <cmath> #include <cstdio> const int COUNT = 100000000; int main() { double sum = 0; for (int i = 1; i <= COUNT; ++i) sum += sqrt(i); printf("%f\n", sum); return 0; } It runs 5.5s on my computer. However, if I change sqrt into std::sqrt , It will run only 0.7s. I know that if I use sqrt , I'm using the function from C library, and if I use std::sqrt , I'm using the one in <cmath> . But <cmath> doesn't define one for int , and if I change the type of i into double , they will run for equal speed. So the compiler isn't optimizing for int . This seems to only

(EDIT: Let's title this, "Lessons in how measurements can go wrong." I still haven't figured out exactly what's causing the discrepancy though.) I found a very fast integer square root function here by Mark Crowne. At least with GCC on my machine, it's clearly the fastest integer square root function I've tested (including the functions in Hacker's Delight, this page , and floor(sqrt()) from the standard library). After cleaning up the formatting a bit, renaming a variable, and using fixed-width types, it looks like this: static uint32_t mcrowne_isqrt(uint32_t val) { uint32_t temp, root = 0;

Soo.. I'm writing a pentagon project for my c++ class, and to be honest I'm not really doing well right now due job and other classes. So.. we need to make a pentagon program that will have Pentagon class and Menu Class. I managed working Menu Class but I'm not sure how to work with Pentagon class. anyways, what I currently need is - to make a right equation with square roots. Equation for finding a Area of pentagon is: A = s^2 sqrt ( of 25 + 10 sqrt (5) ) / (over) 4 So how do I do that? This is what I currently have in my Menu Class: // ================== #include "StdAfx.h" #include <string>