Is std::pow() More Efficient Than Multiplying a Number by Itself?

Which is More Efficient: Using pow() to Square or Multiplying by Itself?

In C, determining the efficiency of pow() for squaring or just multiplying a number by itself (i.e., x*x*x) requires considering specific scenarios.

C

For pow(x, 3) versus x*x*x, x*x*x is generally faster in C because C lacks a pow(double, int) overload.

C

In C , the efficiency of std::pow versus x*x*x depends on the specific exponent. When the exponent is an integer, std::pow(double, int) is called, resulting in similar performance to x*x*x.

However, for non-integer exponents, std::pow uses more complex algorithms and may be faster than x*x*x.

Benchmark Results

Recent benchmarks using newer compilers (e.g., GCC 10, Clang 12) have shown that x*x*x is generally faster for exponents greater than 2. However, std::pow can perform similarly or even better in some cases, especially for odd exponents or when optimizations such as -ffast-math are enabled.

Additional Considerations

• Compiler Optimizations: Modern compilers may optimize repeated multiplications like x*x*x into a single multiplication.
• Mathematical Stability: Using pow() can provide better numerical stability in certain cases.

Conclusion

In most practical scenarios, x*x*x is likely to be more efficient than std::pow in C. In C , the specific exponent and compiler can affect which method is faster. However, it's generally recommended to use pow() for non-integer exponents due to its mathematical stability and potential performance benefits with recent compilers.

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