Is there any advantage to using pow(x,2) instead of x*x, with x double?

by

FWIW, with gcc-4.2 on MacOS X 10.6 and -O3 compiler flags,

x = x * x;

and

y = pow(y, 2);

result in the same assembly code:

#include <cmath>

void test(double& x, double& y) {
        x = x * x;
        y = pow(y, 2);
}

Assembles to:

    pushq   %rbp
    movq    %rsp, %rbp
    movsd   (%rdi), %xmm0
    mulsd   %xmm0, %xmm0
    movsd   %xmm0, (%rdi)
    movsd   (%rsi), %xmm0
    mulsd   %xmm0, %xmm0
    movsd   %xmm0, (%rsi)
    leave
    ret

So as long as you’re using a decent compiler, write whichever makes more sense to your application, but consider that pow(x, 2) can never be more optimal than the plain multiplication.

More Related Contents:

  1. Integer division always zero [duplicate]
  2. How can I write a power function myself?
  3. How computer does floating point arithmetic?
  4. C++ quadratic equation using factorization
  5. Why does changing 0.1f to 0 slow down performance by 10x?
  6. Why does printf() promote a float to a double?
  7. Fast ceiling of an integer division in C / C++
  8. How to achieve smooth tangent space normals?
  9. Most accurate way to do a combined multiply-and-divide operation in 64-bit?
  10. double or float, which is faster? [duplicate]
  11. Floating point equality and tolerances
  12. Representing integers in doubles
  13. Why floating point value such as 3.14 are considered as double by default in MSVC?
  14. Is floating point addition commutative in C++?
  15. Comparing floating point number to zero
  16. Most efficient/elegant way to clip a number?
  17. Compare double to zero using epsilon
  18. How to alter a float by its smallest increment (or close to it)?
  19. Avoiding denormal values in C++
  20. sine wave that slowly ramps up frequency from f1 to f2 for a given time
  21. Impact of cubic and catmull splines on image
  22. How to specify setprecision rounding
  23. What is the maximum length in chars needed to represent any double value?
  24. The behaviour of floating point division by zero
  25. Uses for negative zero floating point value?
  26. What is the size of float and double in C and C++? [duplicate]
  27. Float formatting in C++
  28. std::stod throws out_of_range error for a string that should be valid
  29. Area of rectangle-rectangle intersection
  30. How can I safely average two unsigned ints in C++?

Leave a Comment