When backtracking, bwa-short does not keep the detailed alignment or the exact
start and end positions. To find the boundary and the CIGAR, the old code does
a global alignment with a small end-gap penalty. It then deals with a lot of
special cases to derive the right position and CIGAR, which are actually not
always right. It is a mess.
As the new ksw.{c,h} does not support a different end-gap penalty, the old
strategy does not work. But we get something better. The new code finds the
boundaries with ksw_extend(). It is cleaner and gives more accurate CIGAR in
most cases.
stdaln.{c,h} was written ten years ago. Its local and SW extension code are
actually buggy (though that rarely happens and usually does not affect the
results too much). ksw.{c,h} is more concise, potentially faster, less buggy,
and richer in features.
Added wrappers err_fputc and err_fputs to catch failures in fput and fputs.
Macros err_putchar and err_puts call the new wrappers and can be used in
place of putchar and puts.
To avoid having to make millions of function calls when printing out
sequences, the code to print them in bwa_print_sam1 using putchar has
been replaced by a new version in bwa_print_seq that puts the sequence
into a buffer and then outputs the lot with err_fwrite. In testing, the
new code was slightly faster than the old version, with the added benefit
that it will stop promptly if IO problems are detected.
Rob Davies
Heng Li
Heng Li