ref_n <= 2

it is unpossibale that (left_fix == 0 && right_fix == 0)

window_offset is still the x-based offset x_total_start and y_total_start are global positions, instead of local positions

bfs_round is 3

just merge, don't delete anything

p[]: id of last f[]: the score ending at i, not always the peak v[]: keeps the peak score up to i; t[]: used for buffer min_cnt = 2; min_sc = 30; extr

max_dist is like the overlap length in string graph the end position of qs is li->qs; dst[]->->qlen indicate the region that need to be checked in bas

target_dist should like the overlap length in string graph it should be used to evaluate if the identified path is close to real path/alignment

cannot use tstr in-place