void
mandel_avx(unsigned char *image, const struct spec *s)
{
__m256 xmin = _mm256_set1_ps(s->xlim[0]);
__m256 ymin = _mm256_set1_ps(s->ylim[0]);
__m256 xscale = _mm256_set1_ps((s->xlim[1] - s->xlim[0]) / s->width);
__m256 yscale = _mm256_set1_ps((s->ylim[1] - s->ylim[0]) / s->height);
__m256 threshold = _mm256_set1_ps(4);
__m256 one = _mm256_set1_ps(1);
__m256 iter_scale = _mm256_set1_ps(1.0f / s->iterations);
__m256 depth_scale = _mm256_set1_ps(s->depth - 1);
#pragma omp parallel for schedule(dynamic, 1)
for (int y = 0; y < s->height; y++) {
for (int x = 0; x < s->width; x += 8) {
__m256 mx = _mm256_set_ps(x + 7, x + 6, x + 5, x + 4,
x + 3, x + 2, x + 1, x + 0);
__m256 my = _mm256_set1_ps(y);
__m256 cr = _mm256_add_ps(_mm256_mul_ps(mx, xscale), xmin);
__m256 ci = _mm256_add_ps(_mm256_mul_ps(my, yscale), ymin);
__m256 zr = cr;
__m256 zi = ci;
int k = 1;
__m256 mk = _mm256_set1_ps(k);
while (++k < s->iterations) {
/* Compute z1 from z0 */
__m256 zr2 = _mm256_mul_ps(zr, zr);
__m256 zi2 = _mm256_mul_ps(zi, zi);
__m256 zrzi = _mm256_mul_ps(zr, zi);
/* zr1 = zr0 * zr0 - zi0 * zi0 + cr */
/* zi1 = zr0 * zi0 + zr0 * zi0 + ci */
zr = _mm256_add_ps(_mm256_sub_ps(zr2, zi2), cr);
zi = _mm256_add_ps(_mm256_add_ps(zrzi, zrzi), ci);
/* Increment k */
zr2 = _mm256_mul_ps(zr, zr);
zi2 = _mm256_mul_ps(zi, zi);
__m256 mag2 = _mm256_add_ps(zr2, zi2);
__m256 mask = _mm256_cmp_ps(mag2, threshold, _CMP_LT_OS);
mk = _mm256_add_ps(_mm256_and_ps(mask, one), mk);
/* Early bailout? */
if (_mm256_testz_ps(mask, _mm256_set1_ps(-1)))
break;
}
mk = _mm256_mul_ps(mk, iter_scale);
mk = _mm256_sqrt_ps(mk);
mk = _mm256_mul_ps(mk, depth_scale);
__m256i pixels = _mm256_cvtps_epi32(mk);
unsigned char *dst = image + y * s->width * 3 + x * 3;
unsigned char *src = (unsigned char *)&pixels;
for (int i = 0; i < 8; i++) {
dst[i * 3 + 0] = src[i * 4];
dst[i * 3 + 1] = src[i * 4];
dst[i * 3 + 2] = src[i * 4];
}
}
}
}
INLINE bool any(const avxb& a) {return !_mm256_testz_ps(a,a);}
INLINE bool none(const avxb& a) {return _mm256_testz_ps(a,a) != 0;}
INLINE bool reduce_or (const avxb& a) {return !_mm256_testz_ps(a,a);}
KFR_SINTRIN bool bittestany(const f32avx& x) { return !_mm256_testz_ps(*x, *x); }
