Function partition_mismatch4

Source/astcenc_find_best_partitioning.cpp:314–353

* @brief Compute bit-mismatch for partitioning in 4-partition mode. * * @param a The texel assignment bitvector for the block. * @param b The texel assignment bitvector for the partition table. * * @return The number of bit mismatches. */

 * @return    The number of bit mismatches.
 */
static inline uint8_t partition_mismatch4(
	const uint64_t a[4],
	const uint64_t b[4]
) {
	int p00 = popcount(a[0] ^ b[0]);
	int p01 = popcount(a[0] ^ b[1]);
	int p02 = popcount(a[0] ^ b[2]);
	int p03 = popcount(a[0] ^ b[3]);

	int p10 = popcount(a[1] ^ b[0]);
	int p11 = popcount(a[1] ^ b[1]);
	int p12 = popcount(a[1] ^ b[2]);
	int p13 = popcount(a[1] ^ b[3]);

	int p20 = popcount(a[2] ^ b[0]);
	int p21 = popcount(a[2] ^ b[1]);
	int p22 = popcount(a[2] ^ b[2]);
	int p23 = popcount(a[2] ^ b[3]);

	int p30 = popcount(a[3] ^ b[0]);
	int p31 = popcount(a[3] ^ b[1]);
	int p32 = popcount(a[3] ^ b[2]);
	int p33 = popcount(a[3] ^ b[3]);

	int mx23 = astc::min(p22 + p33, p23 + p32);
	int mx13 = astc::min(p21 + p33, p23 + p31);
	int mx12 = astc::min(p21 + p32, p22 + p31);
	int mx03 = astc::min(p20 + p33, p23 + p30);
	int mx02 = astc::min(p20 + p32, p22 + p30);
	int mx01 = astc::min(p21 + p30, p20 + p31);

	int v0 = p00 + astc::min(p11 + mx23, p12 + mx13, p13 + mx12);
	int v1 = p01 + astc::min(p10 + mx23, p12 + mx03, p13 + mx02);
	int v2 = p02 + astc::min(p11 + mx03, p10 + mx13, p13 + mx01);
	int v3 = p03 + astc::min(p11 + mx02, p12 + mx01, p10 + mx12);

	// Divide by 2 because XOR always counts errors twice, once when missing
	// in the expected position, and again when present in the wrong partition
	return static_cast<uint8_t>(astc::min(v0, v1, v2, v3) / 2);
}

using mismatch_dispatch = unsigned int (*)(const uint64_t*, const uint64_t*);