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Is pow(x, 2) or x * x More Efficient for Squaring in C and C ?

Barbara Streisand
Release: 2024-11-11 10:17:03
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Is pow(x, 2) or x * x More Efficient for Squaring in C and C  ?

What is more efficient? Using pow to square or just multiply it with itself?

In C, using x * x for squaring is generally more efficient than using pow(x, 2) because pow involves a function call with additional overhead.

However, in C , both approaches can be efficient due to compiler optimizations:

pow(x, 3) vs. x x x

In C , pow(x, 3) and x * x * x are usually equivalent in terms of efficiency. C 's std::pow function takes a more generic form (pow(double, double)), which handles exponents as floating-point numbers.

Specific Considerations:

  • Optimization Level: Compilers may optimize either approach.
  • Exponent: As the exponent gets larger, std::pow may become more efficient due to its optimized implementation for integer exponents.
  • Data Types: If you're working with integer exponents and optimizing for speed, manually multiplying (e.g., x * x * x) can still be a better choice.

Here are the updated benchmarks for GCC and Clang, testing efficiency for different exponents:

Exponent GCC (O3) Clang (O3)
2 x * x slightly faster Similar
3 x * x * x faster Similar
4 and above x * x * x * ... faster Similar

Additional Notes:

  • C's pow(double, double) is less efficient than std::pow in C due to the lack of function overloading.
  • Using -ffast-math in GCC can significantly speed up std::pow for odd exponents.

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