pow

Why is 2**100 so much faster than math.pow(2,100)?

由 风流意气都作罢 提交于 2019-12-06 01:29:53
问题 When discussing the question Exponentials in python x.**y vs math.pow(x, y), Alfe stated that there would be no good reason for using math.pow instead of the builtin ** operator in python. timeit shows that math.pow is slower than ** in all cases. What is math.pow() good for anyway? Has anybody an idea where it can be of any advantage then? We tried to convince each other with some timeit arguments an he is the winner so far ;-) -- At least the following timeit results, seem to verify that

Does the implementation of pow() function in C/C++ vary with platform or compiler?

由 我们两清 提交于 2019-12-05 06:34:18
问题 It took a day to debug the built-in pow() function's output. The output differed between my compiler and an online compiler. That is a long story. I have written the following Minimal, Complete, and Verifiable example reproduce the situation. Code: #include <bits/stdc++.h> using namespace std; // This function just prints the binary representation as it is in memory // A modified version of Lightness Races in Orbit's code given here: https://stackoverflow.com/a/37861479/3555000 // I thank

Why does pow(5,2) become 24? [closed]

由 五迷三道 提交于 2019-12-04 22:11:28
I'm making a simple calculator that you can choose a function, then 2 inputs to get your answer. It's a neat little program and everything is running smoothly except for the powers. Every number works correctly. But according to this: 5^2=24, 5^3=624 . I am using pow(number1,number2) . #include <iostream> #include<math.h> using namespace std; int main() { for(;;){ int func; int number1; int number2; cout << "Input your function (+,-,x,/,Square,Power)(1,2,3,4,5,6) "; cin >> func; cout << "input #1: "; cin >> number1; cout << "input #2: "; cin >> number2; if (func==1){ int answer; answer =

Why Does Math.pow(x,y) Count as a Double?

由 。_饼干妹妹 提交于 2019-12-04 17:00:05
问题 I'm writing a Java program to calculate how much food it will take to get a monster to a certain level in My Singing Monsters. When I run the program, it says, "cannot convert from double to int". Can someone explain why this is? Here's the program. int totalFood = 0; int level = 1; int levelMeal = 5*(Math.pow(2,level-1)); int mealNumber = 1; int levelGoal = 1; while(level != levelGoal) { if(mealNumber != 5) { mealNumber += 1; totalFood += levelMeal; } else if(mealNumber == 5) { mealNumber =

Math.pow yields different result depending on java version

由 怎甘沉沦 提交于 2019-12-04 15:01:12
问题 I'm running the following code on a JDK Version 1.7.0_60: System.out.println(Math.pow(1.5476348320352065, (0.3333333333333333))); The result is: 1.1567055833133086 I'm running exactly the same code on a JDK Version 1.7.0. The result is: 1.1567055833133089 I understand that double is not infinitely precise, but was there a change in the java spec that causes the difference? PS: Because we use a legacy system, Big Decimal is not an option. Edit: I was able to track down the time of the change:

Why is printf not using scientific notation?

由 怎甘沉沦 提交于 2019-12-04 11:00:33
问题 I understand that this is a common problem. However I can't find a solid straight answer. 16 ^ 54 = 1.0531229167e+65 (this is the result I want) When I use pow(16,54) , I get: 105312291668557186697918027683670432318895095400549111254310977536.0 Code is as follows: #include <stdio.h> #include <math.h> #include <stdlib.h> void main(){ double public; double a = 16; double b = 54; public = (pow(a,b)); printf("%.21f\n", public); } Code executed with: gcc main.c -lm What I'm doing wrong? 回答1: What

Conversion from double to integer [duplicate]

由 时光毁灭记忆、已成空白 提交于 2019-12-04 06:24:02
问题 This question already has answers here : C++: How to round a double to an int? [duplicate] (5 answers) round() for float in C++ (21 answers) Closed 5 years ago . I am stuck in problem where the double number is not getting properly converted to integer. In this case-> int x=1000; double cuberoot=pow(x,(1/(double)3)); int a=cuberoot; cout<<"cuberoot="<<cuberoot<<endl; cout<<"a="<<a<<endl; Output: cuberoot=10 a=9 Why here a=9 and not 10? Any solution to this problem?? Also I don't want to round

Why is 2**100 so much faster than math.pow(2,100)?

由 橙三吉。 提交于 2019-12-04 05:07:37
When discussing the question Exponentials in python x.**y vs math.pow(x, y) , Alfe stated that there would be no good reason for using math.pow instead of the builtin ** operator in python. timeit shows that math.pow is slower than ** in all cases. What is math.pow() good for anyway? Has anybody an idea where it can be of any advantage then? We tried to convince each other with some timeit arguments an he is the winner so far ;-) -- At least the following timeit results, seem to verify that math.pow is slower than ** in all cases . import timeit print timeit.timeit("math.pow(2, 100)",setup=

Math.pow yields different result depending on java version

由 不打扰是莪最后的温柔 提交于 2019-12-03 09:21:46
I'm running the following code on a JDK Version 1.7.0_60: System.out.println(Math.pow(1.5476348320352065, (0.3333333333333333))); The result is: 1.1567055833133086 I'm running exactly the same code on a JDK Version 1.7.0. The result is: 1.1567055833133089 I understand that double is not infinitely precise, but was there a change in the java spec that causes the difference? PS: Because we use a legacy system, Big Decimal is not an option. Edit: I was able to track down the time of the change: It was introduced in the JDK Version 1.7.0_40 (as compared to Version 1.7.0_25). Oliver Charlesworth

Why is printf not using scientific notation?

由 蓝咒 提交于 2019-12-03 07:49:43
I understand that this is a common problem. However I can't find a solid straight answer. 16 ^ 54 = 1.0531229167e+65 (this is the result I want) When I use pow(16,54) , I get: 105312291668557186697918027683670432318895095400549111254310977536.0 Code is as follows: #include <stdio.h> #include <math.h> #include <stdlib.h> void main(){ double public; double a = 16; double b = 54; public = (pow(a,b)); printf("%.21f\n", public); } Code executed with: gcc main.c -lm What I'm doing wrong? What am I doing wrong? Several things: Use %.10e format for scientific notation with printf for a printout with
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