tinyMathFunctions.c

[詳解]

#include "type.h"
#include "tinyMathFunction.h"

#define INVSQRT_NEWTON_METHOD_NUM (2)

float tInvSqrt(float x) {
    float halfx = 0.5f * x;
    float y = x;
    long i = *(long*)&y;
    i = 0x5f3759df - (i >> 1);
    y = *(float*)&i;
    //ニュートン法
    for (i = 0; i < INVSQRT_NEWTON_METHOD_NUM; i++)
    {
        y = y * (1.5f - (halfx * y * y));
    }
    return y;
}

float tSqrt(float x)
{

    float halfx = 0.5f * x;
    float y = x;
    float val;

    if (x == 0.0f) return 0.0f;

    //invSqrt(y)を計算
    long i = *(long*)&y;
    i = 0x5f3759df - (i >> 1);
    y = *(float*)&i;
    //ニュートン法
    y = y * (1.5f - (halfx * y * y));
    y = y * (1.5f - (halfx * y * y));
    y = y * (1.5f - (halfx * y * y));
    //sqrtを計算
    val = x * y;
    return val;
}



void quickSort(int numbers[], int left, int right)
{
    int pivot, l_hold, r_hold;

    l_hold = left;
    r_hold = right;
    pivot = numbers[left];
    while (left < right)
    {
        while ((numbers[right] >= pivot) && (left < right))
            right--;
        if (left != right)
        {
            numbers[left] = numbers[right];
            left++;
        }
        while ((numbers[left] <= pivot) && (left < right))
            left++;
        if (left != right)
        {
            numbers[right] = numbers[left];
            right--;
        }
    }
    numbers[left] = pivot;
    pivot = left;
    left = l_hold;
    right = r_hold;
    if (left < pivot)
        quickSort(numbers, left, pivot-1);
    if (right > pivot)
        quickSort(numbers, pivot+1, right);
}


/******************************************************************************
**                            End Of File
******************************************************************************/