diff --git a/misc/pafcluster.js b/misc/pafcluster.js
new file mode 100755
index 0000000..d31bbbe
--- /dev/null
+++ b/misc/pafcluster.js
@@ -0,0 +1,174 @@
+#!/usr/bin/env k8
+
+"use strict";
+
+Array.prototype.delete_at = function(i) {
+	for (let j = i; j < this.length - 1; ++j)
+		this[j] = this[j + 1];
+	--this.length;
+}
+
+function* getopt(argv, ostr, longopts) {
+	if (argv.length == 0) return;
+	let pos = 0, cur = 0;
+	while (cur < argv.length) {
+		let lopt = "", opt = "?", arg = "";
+		while (cur < argv.length) { // skip non-option arguments
+			if (argv[cur][0] == "-" && argv[cur].length > 1) {
+				if (argv[cur] == "--") cur = argv.length;
+				break;
+			} else ++cur;
+		}
+		if (cur == argv.length) break;
+		let a = argv[cur];
+		if (a[0] == "-" && a[1] == "-") { // a long option
+			pos = -1;
+			let c = 0, k = -1, tmp = "", o;
+			const pos_eq = a.indexOf("=");
+			if (pos_eq > 0) {
+				o = a.substring(2, pos_eq);
+				arg = a.substring(pos_eq + 1);
+			} else o = a.substring(2);
+			for (let i = 0; i < longopts.length; ++i) {
+				let y = longopts[i];
+				if (y[y.length - 1] == "=") y = y.substring(0, y.length - 1);
+				if (o.length <= y.length && o == y.substring(0, o.length)) {
+					k = i, tmp = y;
+					++c; // c is the number of matches
+					if (o == y) { // exact match
+						c = 1;
+						break;
+					}
+				}
+			}
+			if (c == 1) { // find a unique match
+				lopt = tmp;
+				if (pos_eq < 0 && longopts[k][longopts[k].length-1] == "=" && cur + 1 < argv.length) {
+					arg = argv[cur+1];
+					argv.delete_at(cur + 1);
+				}
+			}
+		} else { // a short option
+			if (pos == 0) pos = 1;
+			opt = a[pos++];
+			let k = ostr.indexOf(opt);
+			if (k < 0) {
+				opt = "?";
+			} else if (k + 1 < ostr.length && ostr[k+1] == ":") { // requiring an argument
+				if (pos >= a.length) {
+					arg = argv[cur+1];
+					argv.delete_at(cur + 1);
+				} else arg = a.substring(pos);
+				pos = -1;
+			}
+		}
+		if (pos < 0 || pos >= argv[cur].length) {
+			argv.delete_at(cur);
+			pos = 0;
+		}
+		if (lopt != "") yield { opt: `--${lopt}`, arg: arg };
+		else if (opt != "?") yield { opt: `-${opt}`, arg: arg };
+		else yield { opt: "?", arg: "" };
+	}
+}
+
+function* k8_readline(fn) {
+	let buf = new Bytes();
+	let file = new File(fn);
+	while (file.readline(buf) >= 0) {
+		yield buf.toString();
+	}
+	file.close();
+	buf.destroy();
+}
+
+function main(args) {
+	let opt = { min_cov:.9, max_dv:.01 };
+	for (const o of getopt(args, "c:d:", [])) {
+		if (o.opt == '-c') opt.min_cov = parseFloat(o.arg);
+		else if (o.opt == '-d') opt.max_dv = parseFloat(o.arg);
+	}
+	if (args.length == 0) {
+		print("Usage: pafcluster.js [options] <ava.paf>");
+		print("Options:");
+		print(`  -c FLOAT     min coverage [${opt.min_cov}]`);
+		print(`  -d FLOAT     max divergence [${opt.max_dv}]`);
+		return;
+	}
+
+	// read
+	let a = [], len = {};
+	for (const line of k8_readline(args[0])) {
+		let m, t = line.split("\t");
+		if (t[4] != "+") continue;
+		const len1 = parseInt(t[1]), len2 = parseInt(t[6]);
+		let s1 = -1, dv = -1.0;
+		for (let i = 12; i < t.length; ++i) {
+			if ((m = /^(s1|dv):\S:(\S+)/.exec(t[i])) != null) {
+				if (m[1] == "s1") s1 = parseInt(m[2]);
+				else if (m[1] == "dv") dv = parseFloat(m[2]);
+			}
+		}
+		if (s1 < 0 || dv < 0) continue;
+		const cov1 = (parseInt(t[3]) - parseInt(t[2])) / len1;
+		const cov2 = (parseInt(t[8]) - parseInt(t[7])) / len2;
+		const min_cov = cov1 < cov2? cov1 : cov2;
+		const max_cov = cov1 > cov2? cov1 : cov2;
+		a.push({ name1:t[0], name2:t[5], len1:len1, len2:len2, min_cov:min_cov, max_cov:max_cov, s1:s1, dv:dv });
+		len[t[0]] = len1, len[t[5]] = len2;
+	}
+	warn(`Read ${a.length} hits`);
+
+	// filter duplicated hits
+	let pair = {}, n_flt = 0, b = [];
+	a.sort(function(x, y) { return y.s1 - x.s1 });
+	for (let i = 0; i < a.length; ++i) {
+		const key = `${a[i].name1}\t${a[i].name2}`;
+		if (pair[key] != null) {
+			++n_flt;
+			continue;
+		}
+		pair[key] = 1;
+		b.push(a[i]);
+	}
+	pair = null;
+	warn(`Filtered ${n_flt} hits`);
+	a = b;
+
+	// core loop
+	while (a.length > 1) {
+		// select the sequence with the highest sum of s1
+		let h = {};
+		for (let i = 0; i < a.length; ++i) {
+			if (h[a[i].name1] == null) h[a[i].name1] = 0;
+			h[a[i].name1] += a[i].s1;
+		}
+		let max_s1 = 0, max_name = "";
+		for (const name in h)
+			if (max_s1 < h[name])
+				max_s1 = h[name], max_name = name;
+		// find contigs in the same group
+		h = {};
+		h[max_name] = 1;
+		for (let i = 0; i < a.length; ++i) {
+			if (a[i].name1 != max_name && a[i].name2 != max_name)
+				continue;
+			if (a[i].min_cov >= opt.min_cov && a[i].dv <= opt.max_dv)
+				h[a[i].name1] = h[a[i].name2] = 1;
+		}
+		let n = 0;
+		for (const key in h) ++n;
+		print(`SD\t${max_name}\t${n}`);
+		for (const key in h) print(`CL\t${key}\t${len[key]}`);
+		print("//");
+		// filter out redundant hits
+		let b = [];
+		for (let i = 0; i < a.length; ++i)
+			if (h[a[i].name1] == null && h[a[i].name2] == null)
+				b.push(a[i]);
+		warn(`Reduced the number of hits from ${a.length} to ${b.length}`);
+		a = b;
+	}
+}
+
+main(arguments);