r849: the pa tag now gives a number

... which is the ratio of this hit to the best ALT hit.

NEWS.md

@@ -12,8 +12,10 @@ having ALT contigs almost has not effect on alignments to the primary assembly
 (seeding may be affected in rare corner cases). At the same time, users may
 get a primary alignment to ALT contigs (no 0x800 flag) if there are no good
 hits to the primary assembly, or get a supplementary alignment to ALT contigs
-if it is better than hits to the primary assembly. Since this release, it is
-recommended to include ALT contigs.
+if it is better than hits to the primary assembly. In the latter case, the
+`pa:f` tag shows the ratio of the primary hit score to the best ALT hit score,
+which is no greater than 1. Since this release, it is recommended to include
+ALT contigs.
 
 Users may consider to use ALT contigs from GRCh38. I am also constructing a
 non-redundant and more complete set of sequences missing from GRCh38.

bwamem.c

@@ -880,13 +880,13 @@ void mem_aln2sam(const mem_opt_t *opt, const bntseq_t *bns, kstring_t *str, bseq
 		for (i = 0; i < n; ++i)
 			if (i != which && !(list[i].flag&0x100)) break;
 		if (i < n) { // there are other primary hits; output them
-			int has_pri_alt = 0;
+			int pri_alt_sc = -1;
 			kputsn("\tSA:Z:", 6, str);
 			for (i = 0; i < n; ++i) {
 				const mem_aln_t *r = &list[i];
 				int k;
 				if (i == which || (list[i].flag&0x100)) continue; // proceed if: 1) different from the current; 2) not shadowed multi hit
-				if (list[i].is_alt) has_pri_alt = 1;
+				if (list[i].is_alt) pri_alt_sc = pri_alt_sc > r->score? pri_alt_sc : r->score;
 				kputs(bns->anns[r->rid].name, str); kputc(',', str);
 				kputl(r->pos+1, str); kputc(',', str);
 				kputc("+-"[r->is_rev], str); kputc(',', str);
@@ -897,7 +897,8 @@ void mem_aln2sam(const mem_opt_t *opt, const bntseq_t *bns, kstring_t *str, bseq
 				kputc(',', str); kputw(r->NM, str);
 				kputc(';', str);
 			}
-			if (has_pri_alt) kputsn("\tpa:A:Y", 7, str);
+			if (pri_alt_sc > 0)
+				ksprintf(str, "\tpa:f:%.3f", (double)p->score / pri_alt_sc);
 		}
 	}
 	if (p->XA) { kputsn("\tXA:Z:", 6, str); kputs(p->XA, str); }

bwamem_extra.c

@@ -59,19 +59,13 @@ void smem_config(smem_i *itr, int min_intv, int max_len, uint64_t max_intv)
 
 const bwtintv_v *smem_next(smem_i *itr)
 {
-	int i, max, max_i, ori_start;
+	int ori_start;
 	itr->tmpvec[0]->n = itr->tmpvec[1]->n = itr->matches->n = itr->sub->n = 0;
 	if (itr->start >= itr->len || itr->start < 0) return 0;
 	while (itr->start < itr->len && itr->query[itr->start] > 3) ++itr->start; // skip ambiguous bases
 	if (itr->start == itr->len) return 0;
 	ori_start = itr->start;
 	itr->start = bwt_smem1a(itr->bwt, itr->len, itr->query, ori_start, itr->min_intv, itr->max_len, itr->max_intv, itr->matches, itr->tmpvec); // search for SMEM
-	if (itr->matches->n == 0) return itr->matches; // well, in theory, we should never come here
-	for (i = max = 0, max_i = 0; i < itr->matches->n; ++i) { // look for the longest match
-		bwtintv_t *p = &itr->matches->a[i];
-		int len = (uint32_t)p->info - (p->info>>32);
-		if (max < len) max = len, max_i = i;
-	}
 	return itr->matches;
 }
 

main.c

@@ -4,7 +4,7 @@
 #include "utils.h"
 
 #ifndef PACKAGE_VERSION
-#define PACKAGE_VERSION "0.7.10-r848-dirty"
+#define PACKAGE_VERSION "0.7.10-r849-dirty"
 #endif
 
 int bwa_fa2pac(int argc, char *argv[]);