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Thread: Computing a cube (power of 3).
 01162009, 05:54 PM #1Member
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Computing a cube (power of 3).
Hello everyone,
I am trying to compute the cube of a bunch of integers, starting from 1 to n.
I am dealing with efficiency and I want to know the fastest way to compute those numbers.
I am currently using x * x * x, rather than Math.pow(x, 3).
I would like to know if my actual solution is the fastest, and if there is any that would be better.
Thank you very much.
 01162009, 06:02 PM #2Senior Member
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I am guessing x * x * x would be faster, right?
 01162009, 06:50 PM #3Senior Member
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If speed is important, always calculate integer powers with combinations of multiplying the current result by itself or by the original number. So extending the logic:
Java Code:x^4 : y = x * x; return y * y; x^5 : y = x * x; return y * y * x; x^6 : y = x * x * x; return y * y; ...
So in general, Math.pow() is an extremely slow way of calculating a power if the exponent is known in advance. (And even for an arbitrary integer exponent, there are still faster ways of doing it.)
Also, on my Pentium, the following:
Java Code:public double power(double x, double y) { return Math.exp(y * Math.log(x)); }
Neil Coffey
Javamex  Java tutorials and performance info
 01162009, 08:07 PM #4Member
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Thanks a lot! That helps me a lot.
Thank you.
 01162009, 10:13 PM #5Member
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