diff --git a/main.c b/main.c
index 0e95bbc..1dae0ac 100644
--- a/main.c
+++ b/main.c
@@ -7,7 +7,7 @@
 #include "mmpriv.h"
 #include "ketopt.h"
 
-#define MM_VERSION "2.18-r1025-dirty"
+#define MM_VERSION "2.18-r1026-dirty"
 
 #ifdef __linux__
 #include <sys/resource.h>
diff --git a/options.c b/options.c
index 7b87f1c..45212dd 100644
--- a/options.c
+++ b/options.c
@@ -26,7 +26,7 @@ void mm_mapopt_init(mm_mapopt_t *opt)
 	opt->max_chain_skip = 25;
 	opt->max_chain_iter = 5000;
 	opt->chain_gap_scale = 1.0f;
-	opt->max_max_occ = 5000;
+	opt->max_max_occ = 4095;
 	opt->occ_dist = 0;
 
 	opt->mask_level = 0.5f;
@@ -91,6 +91,12 @@ int mm_set_opt(const char *preset, mm_idxopt_t *io, mm_mapopt_t *mo)
 		io->flag |= MM_I_HPC, io->k = 19;
 	} else if (strcmp(preset, "map-ont") == 0) {
 		io->flag = 0, io->k = 15;
+	} else if (strcmp(preset, "hifi") == 0 || strcmp(preset, "ccs") == 0) {
+		io->flag = 0, io->k = 19, io->w = 19;
+		mo->a = 1, mo->b = 4, mo->q = 6, mo->q2 = 26, mo->e = 2, mo->e2 = 1;
+		mo->occ_dist = 100;
+		mo->min_mid_occ = 100;
+		mo->min_dp_max = 200;
 	} else if (strcmp(preset, "asm5") == 0) {
 		io->flag = 0, io->k = 19, io->w = 19;
 		mo->a = 1, mo->b = 19, mo->q = 39, mo->q2 = 81, mo->e = 3, mo->e2 = 1, mo->zdrop = mo->zdrop_inv = 200;
diff --git a/seed.c b/seed.c
index 27f7ffe..bd250d9 100644
--- a/seed.c
+++ b/seed.c
@@ -1,23 +1,28 @@
 #include "mmpriv.h"
 #include "kalloc.h"
+#include "ksort.h"
 
-mm_seed_t *mm_seed_collect_all(void *km, const mm_idx_t *mi, const mm128_v *mv)
+mm_seed_t *mm_seed_collect_all(void *km, const mm_idx_t *mi, const mm128_v *mv, int32_t *n_m_)
 {
 	mm_seed_t *m;
 	size_t i;
+	int32_t k;
 	m = (mm_seed_t*)kmalloc(km, mv->n * sizeof(mm_seed_t));
-	for (i = 0; i < mv->n; ++i) {
+	for (i = k = 0; i < mv->n; ++i) {
 		const uint64_t *cr;
-		mm_seed_t *q = &m[i];
+		mm_seed_t *q;
 		mm128_t *p = &mv->a[i];
 		uint32_t q_pos = (uint32_t)p->y, q_span = p->x & 0xff;
 		int t;
 		cr = mm_idx_get(mi, p->x>>8, &t);
+		if (t == 0) continue;
+		q = &m[k++];
 		q->q_pos = q_pos, q->q_span = q_span, q->cr = cr, q->n = t, q->seg_id = p->y >> 32;
 		q->is_tandem = q->flt = 0;
 		if (i > 0 && p->x>>8 == mv->a[i - 1].x>>8) q->is_tandem = 1;
 		if (i < mv->n - 1 && p->x>>8 == mv->a[i + 1].x>>8) q->is_tandem = 1;
 	}
+	*n_m_ = k;
 	return m;
 }
 
@@ -37,18 +42,19 @@ void mm_seed_select(int32_t n, mm_seed_t *a, int len, int max_occ, int max_max_o
 	for (i = 0, last0 = -1; i <= n; ++i) {
 		if (i == n || a[i].n <= max_occ) {
 			if (i - last0 > 1) {
-				int32_t ps = last0 < 0? 0 : (uint32_t)a[last0].q_pos;
-				int32_t pe = i == n? len : (uint32_t)a[i].q_pos;
+				int32_t ps = last0 < 0? 0 : (uint32_t)a[last0].q_pos>>1;
+				int32_t pe = i == n? len : (uint32_t)a[i].q_pos>>1;
 				int32_t j, k, st = last0 + 1, en = i;
 				int32_t max_high_occ = (int32_t)((double)(pe - ps) / dist + .499);
+				//fprintf(stderr, "Y\t%d\t%d\n", ps, pe);
 				if (max_high_occ > MAX_MAX_HIGH_OCC)
 					max_high_occ = MAX_MAX_HIGH_OCC;
 				for (j = st, k = 0; j < en && k < max_high_occ; ++j, ++k)
 					b[k] = (uint64_t)a[j].n<<32 | j;
 				ks_heapmake_uint64_t(k, b); // initialize the binomial heap
 				for (; j < en; ++j) { // if there are more, choose top max_high_occ
-					if (a[j].n < (uint32_t)b[0]) { // then update the heap
-						b[0] = (b[0]&0xFFFFFFFF00000000ULL) | j;
+					if (a[j].n < (int32_t)(b[0]>>32)) { // then update the heap
+						b[0] = (uint64_t)a[j].n<<32 | j;
 						ks_heapdown_uint64_t(0, k, b);
 					}
 				}
@@ -65,21 +71,22 @@ void mm_seed_select(int32_t n, mm_seed_t *a, int len, int max_occ, int max_max_o
 
 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)
 {
-	int rep_st = 0, rep_en = 0, n_m;
+	int rep_st = 0, rep_en = 0, n_m, n_m0;
 	size_t i;
 	mm_seed_t *m;
 	*n_mini_pos = 0;
 	*mini_pos = (uint64_t*)kmalloc(km, mv->n * sizeof(uint64_t));
-	m = mm_seed_collect_all(km, mi, mv);
+	m = mm_seed_collect_all(km, mi, mv, &n_m0);
 	if (dist > 0 && max_max_occ > max_occ) {
-		mm_seed_select(mv->n, m, qlen, max_occ, max_max_occ, dist);
+		mm_seed_select(n_m0, m, qlen, max_occ, max_max_occ, dist);
 	} else {
-		for (i = 0; i < mv->n; ++i)
+		for (i = 0; i < n_m0; ++i)
 			if (m[i].n > max_occ)
 				m[i].flt = 1;
 	}
-	for (i = 0, n_m = 0, *rep_len = 0, *n_a = 0; i < mv->n; ++i) {
+	for (i = 0, n_m = 0, *rep_len = 0, *n_a = 0; i < n_m0; ++i) {
 		mm_seed_t *q = &m[i];
+		//fprintf(stderr, "X\t%d\t%d\t%d\n", q->q_pos>>1, q->n, q->flt);
 		if (q->flt) {
 			int en = (q->q_pos >> 1) + 1, st = en - q->q_span;
 			if (st > rep_en) {