Clamp Array

Clamp every element of an array to the range [lo, hi] in place using AVX2 intrinsics.

Each element should be replaced with lo if it is below lo, hi if it is above hi, or left unchanged if it is already within the range.

Function Signature

#include <immintrin.h>
#include <cstdint>

void clamp_array(int32_t* arr, int n, int32_t lo, int32_t hi);

Parameters:

• arr — pointer to an array of n signed 32-bit integers, guaranteed 32-byte aligned (modified in place)
• n — number of elements, guaranteed to be a multiple of 8 and at least 8
• lo — lower bound of the clamp range
• hi — upper bound of the clamp range (guaranteed lo ≤ hi)

Returns: nothing (array is modified in place)

Example

Input:  arr = [-5, 3, 10, 0, -2, 7, 15, 1], lo = 0, hi = 10
Output: arr = [ 0, 3, 10, 0,  0, 7, 10, 1]

Constraints

• 8 ≤ n ≤ 1,000,000
• n is always a multiple of 8
• All elements are in range [-1,000,000, 1,000,000]
• lo ≤ hi
• arr is 32-byte aligned

Notes

Clamping is just max(lo, min(hi, x)) — or equivalently, min(hi, max(lo, x)). With AVX2, each of these maps to a single intrinsic, making this a clean two-instruction-per-element problem.

Useful Intrinsics