diff --git a/Makefile b/Makefile
index 4118616..90b1cc4 100644
--- a/Makefile
+++ b/Makefile
@@ -8,6 +8,10 @@ PROG=		minimap2
 PROG_EXTRA=	sdust minimap2-lite
 LIBS=		-lm -lz -lpthread
 
+ifneq ($(aarch64),)
+	arm_neon=1
+endif
+
 ifeq ($(arm_neon),) # if arm_neon is not defined
 ifeq ($(sse2only),) # if sse2only is not defined
 	OBJS+=ksw2_extz2_sse41.o ksw2_extd2_sse41.o ksw2_exts2_sse41.o ksw2_extz2_sse2.o ksw2_extd2_sse2.o ksw2_exts2_sse2.o ksw2_dispatch.o
diff --git a/index.c b/index.c
index 0d8a2ae..c9bd01f 100644
--- a/index.c
+++ b/index.c
@@ -358,7 +358,7 @@ static void *worker_pipeline(void *shared, int step, void *in)
 		for (i = 0; i < s->n_seq; ++i) {
 			mm_bseq1_t *t = &s->seq[i];
 			if (t->l_seq > 0)
-				mm_sketch(0, t->seq, t->l_seq, p->mi->w, p->mi->k, t->rid, p->mi->flag&MM_I_HPC, &s->a);
+				mm_sketch2(0, t->seq, t->l_seq, p->mi->w, p->mi->k, t->rid, p->mi->flag&MM_I_HPC, p->mi->flag&MM_I_SYNCMER, &s->a);
 			else if (mm_verbose >= 2)
 				fprintf(stderr, "[WARNING] the length database sequence '%s' is 0\n", t->name);
 			free(t->seq); free(t->name);
@@ -446,7 +446,7 @@ mm_idx_t *mm_idx_str(int w, int k, int is_hpc, int bucket_bits, int n, const cha
 		sum_len += p->len;
 		if (p->len > 0) {
 			a.n = 0;
-			mm_sketch(0, s, p->len, w, k, i, is_hpc, &a);
+			mm_sketch2(0, s, p->len, w, k, i, is_hpc, 0, &a); // TODO: mm_idx_str() doesn't support syncmer
 			mm_idx_add(mi, a.n, a.a);
 		}
 	}
diff --git a/lchain.c b/lchain.c
index d004157..2da543c 100644
--- a/lchain.c
+++ b/lchain.c
@@ -251,7 +251,7 @@ mm128_t *mg_lchain_rmq(int max_dist, int max_dist_inner, int bw, int max_chn_ski
 					   int64_t n, mm128_t *a, int *n_u_, uint64_t **_u, void *km)
 {
 	int32_t *f,*t, *v, n_u, n_v, mmax_f = 0, max_rmq_size = 0, max_drop = bw;
-	int64_t *p, i, i0, st = 0, st_inner = 0, n_iter = 0;
+	int64_t *p, i, i0, st = 0, st_inner = 0;
 	uint64_t *u;
 	lc_elem_t *root = 0, *root_inner = 0;
 	void *mem_mp = 0;
@@ -345,7 +345,6 @@ mm128_t *mg_lchain_rmq(int max_dist, int max_dist_inner, int bw, int max_chn_ski
 						}
 						if (!krmq_itr_prev(lc_elem, &itr)) break;
 					}
-					n_iter += n_rmq_iter;
 				}
 			}
 		}
diff --git a/main.c b/main.c
index 0be9933..af5ffa5 100644
--- a/main.c
+++ b/main.c
@@ -7,7 +7,7 @@
 #include "mmpriv.h"
 #include "ketopt.h"
 
-#define MM_VERSION "2.24-r1122"
+#define MM_VERSION "2.24-r1149-dirty"
 
 #ifdef __linux__
 #include <sys/resource.h>
@@ -121,7 +121,7 @@ static inline void yes_or_no(mm_mapopt_t *opt, int64_t flag, int long_idx, const
 
 int main(int argc, char *argv[])
 {
-	const char *opt_str = "2aSDw:k:K:t:r:f:Vv:g:G:I:d:XT:s:x:Hcp:M:n:z:A:B:O:E:m:N:Qu:R:hF:LC:yYPo:e:U:";
+	const char *opt_str = "2aSDw:k:K:t:r:f:Vv:g:G:I:d:XT:s:x:Hcp:M:n:z:A:B:O:E:m:N:Qu:R:hF:LC:yYPo:e:U:j:";
 	ketopt_t o = KETOPT_INIT;
 	mm_mapopt_t opt;
 	mm_idxopt_t ipt;
@@ -153,7 +153,8 @@ int main(int argc, char *argv[])
 	o = KETOPT_INIT;
 
 	while ((c = ketopt(&o, argc, argv, 1, opt_str, long_options)) >= 0) {
-		if (c == 'w') ipt.w = atoi(o.arg);
+		if (c == 'w') ipt.w = atoi(o.arg), ipt.flag &= ~MM_I_SYNCMER;
+		else if (c == 'j') ipt.w = atoi(o.arg), ipt.flag |= MM_I_SYNCMER;
 		else if (c == 'k') ipt.k = atoi(o.arg);
 		else if (c == 'H') ipt.flag |= MM_I_HPC;
 		else if (c == 'd') fnw = o.arg; // the above are indexing related options, except -I
@@ -322,6 +323,7 @@ int main(int argc, char *argv[])
 		fprintf(fp_help, "    -H           use homopolymer-compressed k-mer (preferrable for PacBio)\n");
 		fprintf(fp_help, "    -k INT       k-mer size (no larger than 28) [%d]\n", ipt.k);
 		fprintf(fp_help, "    -w INT       minimizer window size [%d]\n", ipt.w);
+		fprintf(fp_help, "    -j INT       syncmer submer size (overriding -w) []\n");
 		fprintf(fp_help, "    -I NUM       split index for every ~NUM input bases [4G]\n");
 		fprintf(fp_help, "    -d FILE      dump index to FILE []\n");
 		fprintf(fp_help, "  Mapping:\n");
diff --git a/map.c b/map.c
index 5311468..2342c9e 100644
--- a/map.c
+++ b/map.c
@@ -67,7 +67,7 @@ static void collect_minimizers(void *km, const mm_mapopt_t *opt, const mm_idx_t
 	mv->n = 0;
 	for (i = n = 0; i < n_segs; ++i) {
 		size_t j;
-		mm_sketch(km, seqs[i], qlens[i], mi->w, mi->k, i, mi->flag&MM_I_HPC, mv);
+		mm_sketch2(km, seqs[i], qlens[i], mi->w, mi->k, i, mi->flag&MM_I_HPC, mi->flag&MM_I_SYNCMER, mv);
 		for (j = n; j < mv->n; ++j)
 			mv->a[j].y += sum << 1;
 		if (opt->sdust_thres > 0) // mask low-complexity minimizers
diff --git a/minimap.h b/minimap.h
index 13e12e0..3fb6900 100644
--- a/minimap.h
+++ b/minimap.h
@@ -44,6 +44,7 @@
 #define MM_I_HPC          0x1
 #define MM_I_NO_SEQ       0x2
 #define MM_I_NO_NAME      0x4
+#define MM_I_SYNCMER      0x8
 
 #define MM_IDX_MAGIC   "MMI\2"
 
diff --git a/minimap2.1 b/minimap2.1
index 8a759db..08d9c94 100644
--- a/minimap2.1
+++ b/minimap2.1
@@ -79,6 +79,19 @@ Minimizer k-mer length [15]
 .BI -w \ INT
 Minimizer window size [10]. A minimizer is the smallest k-mer
 in a window of w consecutive k-mers.
+.TP
+.BI -j \ INT
+Syncmer submer size [10]. Option
+.B -j
+and
+.B -w
+will override each: if
+.B -w
+is applied after
+.BR -j ,
+.B -j
+will have no effect, and vice versa.
+
 .TP
 .B -H
 Use homopolymer-compressed (HPC) minimizers. An HPC sequence is constructed by
diff --git a/mmpriv.h b/mmpriv.h
index 2f5034b..7b51b98 100644
--- a/mmpriv.h
+++ b/mmpriv.h
@@ -60,6 +60,8 @@ void radix_sort_64(uint64_t *beg, uint64_t *end);
 uint32_t ks_ksmall_uint32_t(size_t n, uint32_t arr[], size_t kk);
 
 void mm_sketch(void *km, const char *str, int len, int w, int k, uint32_t rid, int is_hpc, mm128_v *p);
+void mm_sketch_syncmer(void *km, const char *str, int len, int smer, int k, uint32_t rid, int is_hpc, mm128_v *p);
+void mm_sketch2(void *km, const char *str, int len, int w, int k, uint32_t rid, int is_hpc, int is_syncmer, mm128_v *p);
 
 mm_seed_t *mm_collect_matches(void *km, int *_n_m, int qlen, int max_occ, int max_max_occ, int dist, const mm_idx_t *mi, const mm128_v *mv, int64_t *n_a, int *rep_len, int *n_mini_pos, uint64_t **mini_pos);
 void mm_seed_mz_flt(void *km, mm128_v *mv, int32_t q_occ_max, float q_occ_frac);
diff --git a/sketch.c b/sketch.c
index f830693..42ab4f7 100644
--- a/sketch.c
+++ b/sketch.c
@@ -141,3 +141,58 @@ void mm_sketch(void *km, const char *str, int len, int w, int k, uint32_t rid, i
 	if (min.x != UINT64_MAX)
 		kv_push(mm128_t, km, *p, min);
 }
+
+void mm_sketch_syncmer(void *km, const char *str, int len, int smer, int k, uint32_t rid, int is_hpc, mm128_v *p)
+{
+	uint64_t shift1 = 2 * (k - 1), mask = (1ULL<<2*k) - 1, smask = (1ULL<<2*smer) - 1, kmer[2] = {0,0};
+	int i, j, l, buf_pos, min_pos, kmer_span = 0;
+	tiny_queue_t tq;
+
+	assert(len > 0 && (smer > 0 && smer <= k) && (k > 0 && k <= 28)); // 56 bits for k-mer; could use long k-mers, but 28 enough in practice
+	memset(&tq, 0, sizeof(tiny_queue_t));
+	kv_resize(mm128_t, km, *p, p->n + len/(k - smer));
+
+	for (i = l = buf_pos = min_pos = 0; i < len; ++i) {
+		int c = seq_nt4_table[(uint8_t)str[i]];
+		if (c < 4) { // not an ambiguous base
+			int z;
+			if (is_hpc) {
+				int skip_len = 1;
+				if (i + 1 < len && seq_nt4_table[(uint8_t)str[i + 1]] == c) {
+					for (skip_len = 2; i + skip_len < len; ++skip_len)
+						if (seq_nt4_table[(uint8_t)str[i + skip_len]] != c)
+							break;
+					i += skip_len - 1; // put $i at the end of the current homopolymer run
+				}
+				tq_push(&tq, skip_len);
+				kmer_span += skip_len;
+				if (tq.count > k) kmer_span -= tq_shift(&tq);
+			} else kmer_span = l + 1 < k? l + 1 : k;
+			kmer[0] = (kmer[0] << 2 | c) & mask;           // forward k-mer
+			kmer[1] = (kmer[1] >> 2) | (3ULL^c) << shift1; // reverse k-mer
+			if (kmer[0] == kmer[1]) continue; // skip "symmetric k-mers" as we don't know it strand
+			z = kmer[0] < kmer[1]? 0 : 1; // strand
+			++l;
+			if (l >= k && kmer_span < 256) {
+				uint64_t x, min = UINT64_MAX;
+				x = hash64(kmer[z], mask);
+				for (j = 0; j < k - smer; ++j) {
+					uint64_t y = x >> (j + j) & smask;
+					min = min < y? min : y;
+				}
+				if ((x & smask) == min) {
+					mm128_t t;
+					t.x = x << 8 | kmer_span;
+					t.y = (uint64_t)rid<<32 | (uint32_t)i<<1 | z;
+					kv_push(mm128_t, km, *p, t);
+				}
+			}
+		} else l = 0, tq.count = tq.front = 0, kmer_span = 0;
+	}
+}
+
+void mm_sketch2(void *km, const char *str, int len, int w, int k, uint32_t rid, int is_hpc, int is_syncmer, mm128_v *p)
+{
+	if (is_syncmer) mm_sketch_syncmer(km, str, len, w, k, rid, is_hpc, p);
+	else mm_sketch(km, str, len, w, k, rid, is_hpc, p);
+}