//mate info is not complete, skip
if (!(((b->core.flag & 0x0040) && (b2->core.flag & 0x0080)) || ((b->core.flag & 0x0080) && (b2->core.flag & 0x0040)))) continue;
//unalignable reads, skip
//mate info is not complete, skip
if (!(((b->core.flag & 0x0040) && (b2->core.flag & 0x0080)) || ((b->core.flag & 0x0080) && (b2->core.flag & 0x0040)))) continue;
//unalignable reads, skip