Fixed a bug in kmer similarity computation where the fact that sequences

could be switched was not accounted for

src/kmer_similarity.c

@@ -72,7 +72,9 @@ Obi_ali_p kmer_similarity(Obiview_p view1, OBIDMS_column_p column1, index_t idx1
 							bool build_consensus)
 {
 	Obi_ali_p       ali = NULL;
-	int i, j;
+	int 			i, j;
+	bool 			switched_seqs;
+	bool			left_ali;
 	OBIDMS_column_p qual_col1;
 	OBIDMS_column_p qual_col2;
 	double 			score = 0.0;
@@ -99,6 +101,7 @@ Obi_ali_p kmer_similarity(Obiview_p view1, OBIDMS_column_p column1, index_t idx1
 	int32_t	        kmer_count;
 	int32_t         best_shift_idx;
 	int32_t         best_shift;
+	int32_t         abs_shift;
 	int32_t         max_common_kmers;
 	int32_t         overlap_len;
 	int32_t         consensus_len;
@@ -137,10 +140,12 @@ Obi_ali_p kmer_similarity(Obiview_p view1, OBIDMS_column_p column1, index_t idx1
 	}
 
 	// Choose the shortest sequence to save kmer positions in array
+	switched_seqs = false;
 	len1 = blob1->length_decoded_value;
 	len2 = blob2->length_decoded_value;
 	if (len2 > len1)
 	{
+		switched_seqs = true;
 		temp_len = len1;
 		len1 = len2;
 		len2 = temp_len;
@@ -355,13 +360,25 @@ Obi_ali_p kmer_similarity(Obiview_p view1, OBIDMS_column_p column1, index_t idx1
 	 	return NULL;
 	}
 
+	abs_shift = abs(best_shift);
+
 	// Save result in Obi_ali structure
 	ali->score = score;
 	ali->consensus_length = 0;
 	ali->overlap_length = overlap_len;
-	ali->shift = best_shift;
+	ali->shift = abs_shift;
 	ali->consensus_seq = NULL;
 	ali->consensus_qual = NULL;
+	if (((best_shift < 0) && (!switched_seqs)) || ((best_shift > 0) && switched_seqs))
+	{
+		left_ali = true;
+		strcpy(ali->direction, "left");
+	}
+	else
+	{
+		left_ali = false;
+		strcpy(ali->direction, "right");
+	}
 
 	// Build the consensus sequence if asked
 	if (build_consensus)
@@ -400,7 +417,7 @@ Obi_ali_p kmer_similarity(Obiview_p view1, OBIDMS_column_p column1, index_t idx1
 		if (seq1 == NULL)
 			seq1 = obi_blob_to_seq(blob1);
 
-		if (best_shift > 0)
+		if (left_ali)
 		    consensus_len = len1 + len2 - overlap_len;
 		else
 		    consensus_len = overlap_len;
@@ -427,26 +444,33 @@ Obi_ali_p kmer_similarity(Obiview_p view1, OBIDMS_column_p column1, index_t idx1
 		ali->consensus_seq = consensus_seq;
 		ali->consensus_qual = consensus_qual;
 
-		// Compute consensus-relative shift for each sequence and store direction
-		if (best_shift >= 0)
+		// Compute consensus-relative shift for each sequence
+		if (best_shift > 0)
 		{
-			shift1 = 0;
-			shift2 = best_shift;
-			strcpy(ali->direction, "left");
+			shift1 = best_shift;
+			shift2 = 0;
 		}
 		else
 		{
-			shift1 = -(best_shift);
-			shift2 = 0;
-			strcpy(ali->direction, "right");
+			shift1 = 0;
+			shift2 = -(best_shift);
 		}
 
-		// If positive shift, copy first part of second sequence
-		if (best_shift > 0)
+		// If left alignment, copy first part of first sequence
+		if (left_ali)
 		{
-			strncpy(consensus_seq, seq2, best_shift);
-			memcpy(consensus_qual, qual2, best_shift*sizeof(uint8_t));
-			cons_shift = best_shift;
+			if (switched_seqs)
+			{
+				strncpy(consensus_seq, seq2, abs_shift);
+				memcpy(consensus_qual, qual2, abs_shift*sizeof(uint8_t));
+				cons_shift = abs_shift;
+			}
+			else
+			{
+				strncpy(consensus_seq, seq1, abs_shift);
+				memcpy(consensus_qual, qual1, abs_shift*sizeof(uint8_t));
+				cons_shift = abs_shift;
+			}
 		}
 		else
 			cons_shift = 0;
@@ -461,11 +485,19 @@ Obi_ali_p kmer_similarity(Obiview_p view1, OBIDMS_column_p column1, index_t idx1
  			consensus_qual[pos+cons_shift] = round((qual1[pos+shift1] + qual2[pos+shift2])/2);    // TODO maybe use the (p1*(1-p2/3)) formula (but parenthesis bug???)
 		}
 
-		// If positive shift, copy last part of first sequence
-		if (best_shift > 0)
+		// If left alignment, copy last part of first sequence
+		if (left_ali)
 		{
-			strncpy(consensus_seq+cons_shift+overlap_len, seq1+overlap_len, len1-overlap_len);
-			memcpy(consensus_qual+cons_shift+overlap_len, qual1+overlap_len, (len1-overlap_len)*sizeof(uint8_t));
+			if (switched_seqs)
+			{
+				strncpy(consensus_seq+cons_shift+overlap_len, seq1+overlap_len, len1-overlap_len);
+				memcpy(consensus_qual+cons_shift+overlap_len, qual1+overlap_len, (len1-overlap_len)*sizeof(uint8_t));
+			}
+			else
+			{
+				strncpy(consensus_seq+cons_shift+overlap_len, seq2+overlap_len, len2-overlap_len);
+				memcpy(consensus_qual+cons_shift+overlap_len, qual2+overlap_len, (len2-overlap_len)*sizeof(uint8_t));
+			}
 		}
 
 		consensus_seq[consensus_len] = '\0';