pow – Tarik Billa

Math.pow yields different result depending on java version

August 31, 2023 by Tarik

but was there a change in the java spec that causes the difference? No.* According to the Javadocs for Math.pow, a difference of up to one ULP (Unit in the Last Place) is permitted. If we take a look at your two values: System.out.printf(“%016x\n”, Double.doubleToLongBits(1.1567055833133086)); System.out.printf(“%016x\n”, Double.doubleToLongBits(1.1567055833133089)); we get: 3ff281ddb6b6e675 3ff281ddb6b6e676 which indeed differ by … Read more

How to: pow(real, real) in x86

August 28, 2023 by Tarik

Just compute it as 2^(y*log2(x)). There is a x86 instruction FYL2X to compute y*log2(x) and a x86 instruction F2XM1 to do exponentiation. F2XM1 requires an argument in [-1,1] range, so you’d have to add some code in between to extract the integer part and the remainder, exponentiate the remainder, use FSCALE to scale the result … Read more

pow() seems to be out by one here

July 23, 2023 by Tarik

pow works with double numbers. These represent numbers of the form s * 2^e where s is a 53 bit integer. Therefore double can store all integers below 2^53, but only some integers above 2^53. In particular, it can only represent even numbers > 2^53, since for e > 0 the value is always a … Read more

Does Java have an exponential operator?

June 30, 2023 by Tarik

There is no operator, but there is a method. Math.pow(2, 3) // 8.0 Math.pow(3, 2) // 9.0 FYI, a common mistake is to assume 2 ^ 3 is 2 to the 3rd power. It is not. The caret is a valid operator in Java (and similar languages), but it is binary xor.

Math.Pow vs multiply operator (performance)

May 19, 2023 by Tarik

I just reinstalled windows so visual studio is not installed and the code is ugly using System; using System.Diagnostics; public static class test{ public static void Main(string[] args){ MyTest(); PowTest(); } static void PowTest(){ var sw = Stopwatch.StartNew(); double res = 0; for (int i = 0; i < 333333333; i++){ res = Math.Pow(i,30); //pow(i,30) … Read more

Why is pow(int, int) so slow?

April 27, 2023 by Tarik

pow() works with real floating-point numbers and uses under the hood the formula pow(x,y) = e^(y log(x)) to calculate x^y. The int are converted to double before calling pow. (log is the natural logarithm, e-based) x^2 using pow() is therefore slower than x*x. Edit based on relevant comments Using pow even with integer exponents may … Read more

Exponentials in python: x**y vs math.pow(x, y)

February 1, 2023 by Tarik

Using the power operator ** will be faster as it won’t have the overhead of a function call. You can see this if you disassemble the Python code: >>> dis.dis(‘7. ** i’) 1 0 LOAD_CONST 0 (7.0) 3 LOAD_NAME 0 (i) 6 BINARY_POWER 7 RETURN_VALUE >>> dis.dis(‘pow(7., i)’) 1 0 LOAD_NAME 0 (pow) 3 LOAD_CONST … Read more

Why is Math.pow(0, 0) === 1?

January 22, 2023 by Tarik

In C++ The result of pow(0, 0) the result is basically implementation defined behavior since mathematically we have a contradictory situation where N^0 should always be 1 but 0^N should always be 0 for N > 0, so you should have no expectations mathematically as to the result of this either. This Wolfram Alpha forum … Read more

How to get the Power of some Integer in Swift language?

December 14, 2022 by Tarik

If you like, you could declare an infix operator to do it. // Put this at file level anywhere in your project infix operator ^^ { associativity left precedence 160 } func ^^ (radix: Int, power: Int) -> Int { return Int(pow(Double(radix), Double(power))) } // … // Then you can do this… let i = … Read more

Why isn’t `int pow(int base, int exponent)` in the standard C++ libraries?

December 9, 2022 by Tarik

As of C++11, special cases were added to the suite of power functions (and others). C++11 [c.math] /11 states, after listing all the float/double/long double overloads (my emphasis, and paraphrased): Moreover, there shall be additional overloads sufficient to ensure that, if any argument corresponding to a double parameter has type double or an integer type, … Read more