Function partition_mismatch3

Source/astcenc_find_best_partitioning.cpp:273–304

* @brief Compute bit-mismatch for partitioning in 3-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_mismatch3(
	const uint64_t a[3],
	const uint64_t b[3]
) {
	int p00 = popcount(a[0] ^ b[0]);
	int p01 = popcount(a[0] ^ b[1]);
	int p02 = popcount(a[0] ^ b[2]);

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

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

	int s0 = p11 + p22;
	int s1 = p12 + p21;
	int v0 = astc::min(s0, s1) + p00;

	int s2 = p10 + p22;
	int s3 = p12 + p20;
	int v1 = astc::min(s2, s3) + p01;

	int s4 = p10 + p21;
	int s5 = p11 + p20;
	int v2 = astc::min(s4, s5) + p02;

	// 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) / 2);
}

/**
 * @brief Compute bit-mismatch for partitioning in 4-partition mode.