diff --git a/bwamem.c b/bwamem.c
index 2d326e2..88086ee 100644
--- a/bwamem.c
+++ b/bwamem.c
@@ -14,17 +14,6 @@
 #include "kvec.h"
 #include "ksort.h"
 
-void mem_fill_scmat(int a, int b, int8_t mat[25])
-{
-	int i, j, k;
-	for (i = k = 0; i < 4; ++i) {
-		for (j = 0; j < 4; ++j)
-			mat[k++] = i == j? a : -b;
-		mat[k++] = 0; // ambiguous base
-	}
-	for (j = 0; j < 5; ++j) mat[k++] = 0;
-}
-
 /* Theory on probability and scoring *ungapped* alignment
  *
  * s'(a,b) = log[P(b|a)/P(b)] = log[4P(b|a)], assuming uniform base distribution
@@ -64,12 +53,23 @@ mem_opt_t *mem_opt_init()
 	o->split_factor = 1.5;
 	o->chunk_size = 10000000;
 	o->n_threads = 1;
-	o->pe_dir = 0<<1|1;
 	o->pen_unpaired = 9;
+	o->max_matesw = 100;
 	mem_fill_scmat(o->a, o->b, o->mat);
 	return o;
 }
 
+void mem_fill_scmat(int a, int b, int8_t mat[25])
+{
+	int i, j, k;
+	for (i = k = 0; i < 4; ++i) {
+		for (j = 0; j < 4; ++j)
+			mat[k++] = i == j? a : -b;
+		mat[k++] = 0; // ambiguous base
+	}
+	for (j = 0; j < 5; ++j) mat[k++] = 0;
+}
+
 /***************************
  * SMEM iterator interface *
  ***************************/
diff --git a/bwamem.h b/bwamem.h
index 6ab2b01..d99a9da 100644
--- a/bwamem.h
+++ b/bwamem.h
@@ -18,18 +18,22 @@ typedef struct __smem_i smem_i;
 #define MEM_F_NO_MULTI  0x16
 
 typedef struct {
-	int a, b, q, r, w;
-	int flag;
-	int split_width;
-	int min_seed_len, max_occ, max_chain_gap;
-	int n_threads, chunk_size;
-	int pe_dir;
-	float mask_level;
-	float chain_drop_ratio;
-	float split_factor; // split into a seed if MEM is longer than min_seed_len*split_factor
-	int pen_unpaired; // phred-scaled penalty for unpaired reads
-	int max_ins; // maximum insert size
-	int8_t mat[25]; // scoring matrix; mat[0] == 0 if unset
+	int a, b, q, r;         // match score, mismatch penalty and gap open/extension penalty. A gap of size k costs q+k*r
+	int w;                  // band width
+	int flag;               // see MEM_F_* macros
+	int min_seed_len;       // minimum seed length
+	float split_factor;     // split into a seed if MEM is longer than min_seed_len*split_factor
+	int split_width;        // split into a seed if its occurence is smaller than this value
+	int max_occ;            // skip a seed if its occurence is larger than this value
+	int max_chain_gap;      // do not chain seed if it is max_chain_gap-bp away from the closest seed
+	int n_threads;          // number of threads
+	int chunk_size;         // process chunk_size-bp sequences in a batch
+	float mask_level;       // regard a hit as redundant if the overlap with another better hit is over mask_level times the min length of the two hits
+	float chain_drop_ratio; // drop a chain if its seed coverage is below chain_drop_ratio times the seed coverage of a better chain overlapping with the small chain
+	int pen_unpaired;       // phred-scaled penalty for unpaired reads
+	int max_ins;            // when estimating insert size distribution, skip pairs with insert longer than this value
+	int max_matesw;         // perform maximally max_matesw rounds of mate-SW for each end
+	int8_t mat[25];         // scoring matrix; mat[0] == 0 if unset
 } mem_opt_t;
 
 typedef struct {
diff --git a/bwamem_pair.c b/bwamem_pair.c
index 51f51c9..3ef71ea 100644
--- a/bwamem_pair.c
+++ b/bwamem_pair.c
@@ -246,7 +246,7 @@ int mem_sam_pe(const mem_opt_t *opt, const bntseq_t *bns, const uint8_t *pac, co
 			if (a[i].a[j].score >= a[i].a[0].score  - opt->pen_unpaired)
 				kv_push(mem_alnreg_t, b[i], a[i].a[j]);
 	for (i = 0; i < 2; ++i)
-		for (j = 0; j < b[i].n; ++j)
+		for (j = 0; j < b[i].n && j < opt->max_matesw; ++j)
 			n += mem_matesw(opt, bns->l_pac, pac, pes, &b[i].a[j], s[!i].l_seq, (uint8_t*)s[!i].seq, &a[!i]);
 	free(b[0].a); free(b[1].a);
 	mem_mark_primary_se(opt, a[0].n, a[0].a);
diff --git a/fastmap.c b/fastmap.c
index 77b3d75..b4f8ea8 100644
--- a/fastmap.c
+++ b/fastmap.c
@@ -26,8 +26,9 @@ int main_mem(int argc, char *argv[])
 	void *ko = 0, *ko2 = 0;
 
 	opt = mem_opt_init();
-	while ((c = getopt(argc, argv, "paMCPHk:c:v:s:r:t:R:A:B:O:E:")) >= 0) {
+	while ((c = getopt(argc, argv, "paMCPHk:c:v:s:r:t:R:A:B:O:E:w:")) >= 0) {
 		if (c == 'k') opt->min_seed_len = atoi(optarg);
+		else if (c == 'w') opt->w = atoi(optarg);
 		else if (c == 'A') opt->a = atoi(optarg);
 		else if (c == 'B') opt->b = atoi(optarg);
 		else if (c == 'O') opt->q = atoi(optarg);
@@ -52,6 +53,7 @@ int main_mem(int argc, char *argv[])
 		fprintf(stderr, "Algorithm options:\n\n");
 		fprintf(stderr, "       -t INT     number of threads [%d]\n", opt->n_threads);
 		fprintf(stderr, "       -k INT     minimum seed length [%d]\n", opt->min_seed_len);
+		fprintf(stderr, "       -w INT     band width for banded alignment [%d]\n", opt->w);
 		fprintf(stderr, "       -r FLOAT   look for internal seeds inside a seed longer than {-k} * FLOAT [%g]\n", opt->split_factor);
 		fprintf(stderr, "       -s INT     look for internal seeds inside a seed with less than INT occ [%d]\n", opt->split_width);
 		fprintf(stderr, "       -c INT     skip seeds with more than INT occurrences [%d]\n", opt->max_occ);
diff --git a/main.c b/main.c
index 74980c9..9ef33fa 100644
--- a/main.c
+++ b/main.c
@@ -4,7 +4,7 @@
 #include "utils.h"
 
 #ifndef PACKAGE_VERSION
-#define PACKAGE_VERSION "0.6.2-r277-beta"
+#define PACKAGE_VERSION "0.6.2-r278-beta"
 #endif
 
 static int usage()