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More portable code

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Luis Ángel San Martín 2024-08-31 14:27:27 +02:00
parent 8f42aae53a
commit 35c88edf2d
1 changed files with 42 additions and 2 deletions
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44
image_processing/resize_image.cpp
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@ -76,13 +76,53 @@ QPixmap scalePixmapArea(const QPixmap &pixmap, int width, int height)
// Define SIMD intrinsics for different platforms
#if defined(__AVX__) || defined(__AVX2__)
// Function to normalize angles in radians to the range [-PI, PI]
__m256d normalize_angle(__m256d x)
{
const __m256d pi = _mm256_set1_pd(M_PI);
const __m256d two_pi = _mm256_set1_pd(2 * M_PI);
// Calculate the quotient of x / (2*PI)
__m256d quotient = _mm256_div_pd(x, two_pi);
// Use floor to get the nearest lower integer
quotient = _mm256_floor_pd(quotient);
// Calculate the remainder
__m256d remainder = _mm256_sub_pd(x, _mm256_mul_pd(quotient, two_pi));
// Adjust the range to [-PI, PI]
__m256d adjust = _mm256_cmp_pd(remainder, pi, _CMP_GT_OS);
remainder = _mm256_sub_pd(remainder, _mm256_and_pd(adjust, two_pi));
return remainder;
}
// Improved sine approximation function for __m256d using the normalized angle
__m256d sin_pd_approx(__m256d x)
{
x = normalize_angle(x); // Normalize x to the range [-PI, PI]
// Sine approximation coefficients
const __m256d a0 = _mm256_set1_pd(-0.16666666666666666);
const __m256d a1 = _mm256_set1_pd(0.008333333333333333);
const __m256d a2 = _mm256_set1_pd(-0.0001984126984126984);
__m256d x2 = _mm256_mul_pd(x, x);
__m256d x3 = _mm256_mul_pd(x2, x);
__m256d x5 = _mm256_mul_pd(x3, x2);
__m256d x7 = _mm256_mul_pd(x5, x2);
// Compute the polynomial approximation
__m256d result = _mm256_add_pd(x, _mm256_mul_pd(a0, x3));
result = _mm256_add_pd(result, _mm256_mul_pd(a1, x5));
result = _mm256_add_pd(result, _mm256_mul_pd(a2, x7));
return result;
}
inline __m256d lanczosKernelAVX(const __m256d &x, const __m256d &a_val)
{
__m256d zero = _mm256_setzero_pd();
__m256d one = _mm256_set1_pd(1.0);
__m256d pix = _mm256_mul_pd(_mm256_set1_pd(M_PI), x);
__m256d sin_pix = _mm256_sin_pd(pix);
__m256d sin_pix_a = _mm256_sin_pd(_mm256_div_pd(pix, a_val));
__m256d sin_pix = sin_pd_approx(pix);
__m256d sin_pix_a = sin_pd_approx(_mm256_div_pd(pix, a_val));
__m256d numerator = _mm256_mul_pd(_mm256_mul_pd(a_val, sin_pix), sin_pix_a);
__m256d denominator = _mm256_mul_pd(pix, pix);
__m256d result = _mm256_div_pd(numerator, denominator);