How Can You Implement an Accurate Integer Log2 Function for Binary Tree Operations in C ?

Logarithmic Calculations in C : Integer Log2 Implementation

In C , the need arises for an integer log2() function to determine levels in binary tree structures. However, concern arises when edge elements approach values of 2^n, potentially leading to rounding errors in floating-point log calculations.

To address this issue, an efficient solution involves utilizing the bsr instruction on modern x86 or x86-64 platforms. This instruction returns the position of the highest set bit in an unsigned integer, which is identical to log2().

Here's a C or C function that invokes bsr using inline ASM:

#include <stdint.h>
static inline uint32_t log2(const uint32_t x) {
  uint32_t y;
  asm ( "\tbsr %1, %0\n"
      : "=r"(y)
      : "r" (x)
  );
  return y;
}

By leveraging this technique, you can obtain accurate integer log2() calculations for binary tree operations, ensuring the precision needed for proper indexing and level determination.

The above is the detailed content of How Can You Implement an Accurate Integer Log2 Function for Binary Tree Operations in C ?. For more information, please follow other related articles on the PHP Chinese website!