How do I calculate power-of in C#?

Question

I'm not that great with maths and C# doesn't seem to provide a power-of function so I was wondering if anyone knows how I would run a calculation like this:

var dimensions = ((100*100) / (100.00^3.00));

So `var dimensions = 1.0f/100`? :) – CompuChip Jun 04 '17 at 13:55 — CompuChip, Jun 04 '17 at 13:55

Paul Turner · Accepted Answer · 2013-09-03T09:13:11.550

95

See Math.Pow. The function takes a value and raises it to a specified power:

Math.Pow(100.00, 3.00); // 100.00 ^ 3.00

edited Sep 03 '13 at 09:13

answered Sep 02 '09 at 09:08

Paul Turner

38,949
15
102
166

thanks this was the final calculation: var dimensions = (100*100)/(Math.Pow(100.00, 3.00)); – davethecoder Sep 02 '09 at 09:37

score 15 · Answer 2 · edited Nov 08 '18 at 07:58

15

You are looking for the static method Math.Pow().

edited Nov 08 '18 at 07:58

Gerhard

6,850
8
51
81

answered Sep 02 '09 at 09:07

Daniel Brückner

59,031
16
99
143

score 6 · Answer 3 · answered Sep 02 '09 at 09:10

6

The function you want is Math.Pow in System.Math.

answered Sep 02 '09 at 09:10

AakashM

62,551
17
151
186

H. Pauwelyn · Answer 4 · 2022-09-24T13:41:06.820

I'm answering this question because I don't find any answer why the ^ don't work for powers. The ^ operator in C# is an exclusive or operator shorten as XOR. The truth table of A ^ B shows that it outputs true whenever the inputs differ:

Input A	Input B	Output
0	0	0
0	1	1
1	0	1
1	1	0

Witch means that 100 ^ 3 does this calculation under the hood:

decimal   binary
    100 = 0110 0100 
      3 = 0000 0011
    ---   --------- ^
    103 = 0110 0111

With is of course not the same as Math.Pow(100, 3) with results to one million. You can use that or one of the other existing answers.

You could also shorten your code to this that gives the same result because C# respects the order of operations.

double dimensions = 100 * 100 / Math.Pow(100, 3); // == 0.01

score 4 · Answer 5 · answered Jun 04 '17 at 13:37

4

Do not use Math.Pow

When i use

for (int i = 0; i < 10e7; i++)
{
    var x3 = x * x * x;
    var y3 = y * y * y;
}

It only takes 230 ms whereas the following takes incredible 7050 ms:

for (int i = 0; i < 10e7; i++)
{
    var x3 = Math.Pow(x, 3);
    var y3 = Math.Pow(x, 3);
}

answered Jun 04 '17 at 13:37

Christopher Aicher

95
6

Good, we all expected Math.Pow to be slower. But not that much. Why? Now let's make homework and check what's the **compiler generated code** (both cs and assembly after JIT) and you might be surprised. Try... – Adriano Repetti Jun 04 '17 at 13:42
I was going to rework this one https://github.com/THEjoezack/ColorMine/tree/master/ColorMine/ColorSpaces because there is something like `x*x*x` where I though I could use `x^3`, what I couldnt, so I tried `Math.Pow` In the Reference Source of math.cs I found this one `public static extern double Pow(double x, double y);` So I was not able to look into the code, what did I wrong? – Christopher Aicher Jun 04 '17 at 13:47
What should I find out there? – Christopher Aicher Jun 04 '17 at 14:08
4

Your version is faster because your version only uses integers, how would you do `x^x` for example? – zedling Oct 10 '17 at 17:19
1

@zedling are you sure that is the reason? I just tried it where x is a double with many decimal places and got the same results! (231ms vs 4870ms): https://dotnetfiddle.net/jgNDfm – Ben Aug 22 '19 at 14:40
Nope, and after some searching I've found this: https://stackoverflow.com/a/936548/4308297 – zedling Aug 27 '19 at 10:46

score 3 · Answer 6 · answered Sep 26 '19 at 06:22

Following is the code calculating power of decimal value for RaiseToPower for both -ve and +ve values.

public decimal Power(decimal number, decimal raiseToPower)
        {
            decimal result = 0;
            if (raiseToPower < 0)
            {
                raiseToPower *= -1;
                result = 1 / number;
                for (int i = 1; i < raiseToPower; i++)
                {
                    result /= number;
                }
            }
            else
            {
                result = number;
                for (int i = 0; i <= raiseToPower; i++)
                {
                    result *= number;
                }
            }
            return result;
        }

score 2 · Answer 7 · answered May 04 '20 at 08:25

2

For powers of 2:

var twoToThePowerOf = 1 << yourExponent;
// eg: 1 << 12 == 4096

answered May 04 '20 at 08:25

jeromej

10,508
2
43
62

score 0 · Answer 8 · answered Jun 27 '18 at 21:51

0

Math.Pow() returns double so nice would be to write like this:

double d = Math.Pow(100.00, 3.00);

answered Jun 27 '18 at 21:51

prosti

42,291
14
186
151

score 0 · Answer 9 · answered Oct 03 '21 at 17:48

static void Main(string[] args)
        {
            int i = 2;
            int n = -2;
            decimal y = 1;
            if (n > 0)
            {
                for (int x = 1; x <= n; x++)
                    y *= i;               
            }
            if (n < 0)
            {
                for (int x = -1; x >= n; x--)
                    y /= i;
            }
            Console.WriteLine(y);
        }

How do I calculate power-of in C#?

9 Answers9

Linked