diff --git a/src/emu/sort.c b/src/emu/sort.c
index fd007e2..45cdf95 100644
--- a/src/emu/sort.c
+++ b/src/emu/sort.c
@@ -19,6 +19,58 @@ cmp_int64(const void *a, const void *b)
 		return 0;
 }
 
+/** Replaces the value old in the array arr by new, while keeping the
+ * array arr sorted.
+ *
+ * Preconditions:
+ *  - arr is sorted
+ *  - old is in arr
+ *  - old != new
+ */
+void
+sort_replace(int64_t *arr, int64_t n, int64_t old, int64_t new)
+{
+	if (unlikely(old == new))
+		die("old == new");
+
+	/* Remove the old first then insert the new */
+	if (old < new) {
+		int64_t i = 0;
+
+		/* Quick jump to middle if less than old */
+		int64_t m = n / 2;
+		if (arr[m] < old)
+			i = m;
+
+		/* Skip content until old, no need to copy */
+		for (; arr[i] < old; i++)
+			;
+
+		/* Copy middle section replacing old */
+		for (; arr[i + 1] <= new && i < n - 1; i++)
+			arr[i] = arr[i + 1];
+
+		/* Place new */
+		arr[i] = new;
+	} else { /* new < old */
+		int64_t i = 0;
+
+		/* Find old, must be found */
+		for (; arr[i] < old; i++)
+			;
+
+		/* Shift right to replace old */
+		for (; arr[i - 1] > new && i > 0; i--)
+			arr[i] = arr[i - 1];
+
+		/* Invariant: Either i == 0 or arr[i] <= new
+		 * and the element arr[i] must be gone */
+
+		/* Place new */
+		arr[i] = new;
+	}
+}
+
 /** Called when an input channel changes its value */
 static int
 sort_cb_input(struct chan *in_chan, void *ptr)
@@ -32,27 +84,47 @@ sort_cb_input(struct chan *in_chan, void *ptr)
 		return -1;
 	}
 
-	int64_t vcur = 0;
+	int64_t new = 0;
 	if (cur.type == VALUE_INT64)
-		vcur = cur.i;
+		new = cur.i;
 
 	int64_t index = input->index;
-	int64_t last = sort->values[index];
+	int64_t old = sort->values[index];
 
 	/* Nothing to do if no change */
-	if (last == vcur)
+	if (old == new)
 		return 0;
 
 	dbg("sort input %s changed", in_chan->name);
 
 	/* Otherwise recompute the outputs */
-	sort->values[index] = vcur;
-	memcpy(sort->sorted, sort->values, sort->n * sizeof(int64_t));
-	qsort(sort->sorted, sort->n, sizeof(int64_t), cmp_int64);
+	sort->values[index] = new;
+
+	if (likely(sort->copied)) {
+		sort_replace(sort->sorted, sort->n, old, new);
+	} else {
+		memcpy(sort->sorted, sort->values, sort->n * sizeof(int64_t));
+		qsort(sort->sorted, sort->n, sizeof(int64_t), cmp_int64);
+		sort->copied = 1;
+	}
 
 	for (int64_t i = 0; i < sort->n; i++) {
 		struct value val = value_int64(sort->sorted[i]);
-		if (chan_set(sort->outputs[i], val) != 0) {
+		struct value last;
+		if (chan_read(&sort->outputs[i], &last) != 0) {
+			err("chan_read failed");
+			return -1;
+		}
+
+		if (value_is_equal(&last, &val))
+			continue;
+
+		char buf[128];
+		dbg("writting value %s into channel %s",
+				value_str(val, buf),
+				sort->outputs[i].name);
+
+		if (chan_set(&sort->outputs[i], val) != 0) {
 			err("chan_set failed");
 			return -1;
 		}
@@ -62,7 +134,7 @@ sort_cb_input(struct chan *in_chan, void *ptr)
 }
 
 int
-sort_init(struct sort *sort, struct bay *bay, int64_t n)
+sort_init(struct sort *sort, struct bay *bay, int64_t n, const char *name)
 {
 	memset(sort, 0, sizeof(struct sort));
 	sort->bay = bay;
@@ -72,7 +144,7 @@ sort_init(struct sort *sort, struct bay *bay, int64_t n)
 		err("calloc failed:");
 		return -1;
 	}
-	sort->outputs = calloc(n, sizeof(struct chan *));
+	sort->outputs = calloc(n, sizeof(struct chan));
 	if (sort->outputs == NULL) {
 		err("calloc failed:");
 		return -1;
@@ -88,6 +160,25 @@ sort_init(struct sort *sort, struct bay *bay, int64_t n)
 		return -1;
 	}
 
+	/* Init and register outputs */
+	for (int64_t i = 0; i < n; i++) {
+		struct chan *out = &sort->outputs[i];
+		chan_init(out, CHAN_SINGLE, "%s.out%ld", name, i);
+
+		/* The sort module may write multiple times to the same
+		 * channel if we update more than one input. */
+		chan_prop_set(out, CHAN_DIRTY_WRITE, 1);
+
+		/* No duplicate checks are done by sort module, so we
+		 * simply allow them */
+		chan_prop_set(out, CHAN_DUPLICATES, 1);
+
+		if (bay_register(bay, out) != 0) {
+			err("bay_register out%ld failed", i);
+			return -1;
+		}
+	}
+
 	return 0;
 }
 
@@ -113,22 +204,8 @@ sort_set_input(struct sort *sort, int64_t index, struct chan *chan)
 	return 0;
 }
 
-int
-sort_set_output(struct sort *sort, int64_t index, struct chan *chan)
+struct chan *
+sort_get_output(struct sort *sort, int64_t index)
 {
-	if (sort->outputs[index] != NULL) {
-		err("output %d already has a channel", index);
-		return -1;
-	}
-
-	sort->outputs[index] = chan;
-
-	/* The sort module may write multiple times to the same channel if we
-	 * update more than one input. */
-	chan_prop_set(chan, CHAN_DIRTY_WRITE, 1);
-
-	/* No duplicate checks are done by sort module, so we simply allow them */
-	chan_prop_set(chan, CHAN_DUPLICATES, 1);
-
-	return 0;
+	return &sort->outputs[index];
 }
diff --git a/src/emu/sort.h b/src/emu/sort.h
index c6c72ed..0c3d44a 100644
--- a/src/emu/sort.h
+++ b/src/emu/sort.h
@@ -18,15 +18,17 @@ struct sort_input {
 struct sort {
 	int64_t n;
 	struct sort_input *inputs;
-	struct chan **outputs;
+	struct chan *outputs;
 	int64_t *values;
 	int64_t *sorted;
+	int copied;
 	struct bay *bay;
 };
 
-USE_RET int sort_init(struct sort *sort, struct bay *bay, int64_t n);
+USE_RET int sort_init(struct sort *sort, struct bay *bay, int64_t n, const char *name);
+        void sort_replace(int64_t *arr, int64_t n, int64_t old, int64_t new);
 USE_RET int sort_set_input(struct sort *sort, int64_t index, struct chan *input);
-USE_RET int sort_set_output(struct sort *sort, int64_t index, struct chan *output);
+USE_RET struct chan *sort_get_output(struct sort *sort, int64_t index);
 USE_RET int sort_register(struct sort *sort, struct bay *bay);
 
 #endif /* SORT_H */
diff --git a/test/unit/CMakeLists.txt b/test/unit/CMakeLists.txt
index 13e796a..031796a 100644
--- a/test/unit/CMakeLists.txt
+++ b/test/unit/CMakeLists.txt
@@ -16,3 +16,4 @@ unit_test(value.c)
 unit_test(version.c)
 unit_test(path.c)
 unit_test(sort.c)
+unit_test(sort_replace.c)
diff --git a/test/unit/sort.c b/test/unit/sort.c
index cbc9580..f756250 100644
--- a/test/unit/sort.c
+++ b/test/unit/sort.c
@@ -32,46 +32,39 @@ test_sort(void)
 	bay_init(&bay);
 
 	struct chan inputs[N];
-	struct chan outputs[N];
 
-	for (int i = 0; i < N; i++) {
+	for (int i = 0; i < N; i++)
 		chan_init(&inputs[i], CHAN_SINGLE, "input.%d", i);
-		chan_init(&outputs[i], CHAN_SINGLE, "output.%d", i);
-	}
 
 	/* Register all channels in the bay */
-	for (int i = 0; i < N; i++) {
+	for (int i = 0; i < N; i++)
 		OK(bay_register(&bay, &inputs[i]));
-		OK(bay_register(&bay, &outputs[i]));
-	}
 
 	/* Setup channel values */
-	for (int i = 0; i < N; i++) {
+	for (int i = 0; i < N; i++)
 		OK(chan_set(&inputs[i], value_int64(0)));
-	}
 
 	OK(bay_propagate(&bay));
 
 	struct sort sort;
-	OK(sort_init(&sort, &bay, N));
+	OK(sort_init(&sort, &bay, N, "sort0"));
 
-	for (int i = 0; i < N; i++) {
+	for (int i = 0; i < N; i++)
 		OK(sort_set_input(&sort, i, &inputs[i]));
-		OK(sort_set_output(&sort, i, &outputs[i]));
-	}
 
-	for (int i = 0; i < 2; i++) {
+	for (int i = 0; i < 2; i++)
 		OK(chan_set(&inputs[i], value_int64(1)));
-	}
 
 	OK(bay_propagate(&bay));
 
 	/* Check the outputs */
 	for (int i = 0; i < N - 2; i++) {
-		check_output(&outputs[i], value_int64(0));
+		struct chan *out = sort_get_output(&sort, i);
+		check_output(out, value_int64(0));
 	}
 	for (int i = N - 2; i < N; i++) {
-		check_output(&outputs[i], value_int64(1));
+		struct chan *out = sort_get_output(&sort, i);
+		check_output(out, value_int64(1));
 	}
 }
 
diff --git a/test/unit/sort_replace.c b/test/unit/sort_replace.c
new file mode 100644
index 0000000..f5df69a
--- /dev/null
+++ b/test/unit/sort_replace.c
@@ -0,0 +1,106 @@
+/* Copyright (c) 2021-2023 Barcelona Supercomputing Center (BSC)
+ * SPDX-License-Identifier: GPL-3.0-or-later */
+
+#include "emu/sort.h"
+#include "common.h"
+#include "unittest.h"
+
+static int64_t
+randint(void)
+{
+	return rand() % 1000;
+}
+
+static int
+cmp_int64(const void *a, const void *b)
+{
+	int64_t aa = *(const int64_t *) a;
+	int64_t bb = *(const int64_t *) b;
+
+	if (aa < bb)
+		return -1;
+	else if (aa > bb)
+		return +1;
+	else
+		return 0;
+}
+
+static void
+test_case(int64_t n, int64_t run)
+{
+	srand(run);
+	int64_t *arr = calloc(n, sizeof(int64_t));
+
+	if (arr == NULL)
+		die("calloc failed:");
+
+	for (int64_t i = 0; i < n; i++)
+		arr[i] = randint();
+
+	qsort(arr, n, sizeof(int64_t), cmp_int64);
+
+	int64_t *copy = calloc(n, sizeof(int64_t));
+
+	if (copy == NULL)
+		die("calloc failed:");
+
+	memcpy(copy, arr, n * sizeof(int64_t));
+
+	int64_t iold = rand() % n;
+	int64_t old = arr[iold];
+	int64_t new = randint();
+
+	/* Ensure old != new */
+	while (old == new)
+		new = randint();
+
+	dbg("-- CASE run=%ld n=%ld iold=%ld old=%ld new=%ld\n",
+			run, n, iold, old, new);
+
+	dbg("Contents before sort: ");
+	for (int64_t i = 0; i < n; i++) {
+		dbg("i=%ld, arr[i]=%ld, copy[i]=%ld\n",
+				i, arr[i], copy[i]);
+	}
+
+	sort_replace(arr, n, old, new);
+
+	copy[iold] = new;
+	qsort(copy, n, sizeof(int64_t), cmp_int64);
+
+	dbg("Contents after sort: ");
+	for (int64_t i = 0; i < n; i++) {
+		dbg("i=%ld, arr[i]=%ld, copy[i]=%ld\n",
+				i, arr[i], copy[i]);
+	}
+
+	if (memcmp(arr, copy, n * sizeof(int64_t)) == 0)
+		return;
+
+	die("mismatch");
+}
+
+static void
+test_sort_replace(void)
+{
+	int64_t nmin = 2;
+	int64_t nmax = 300;
+	int64_t nrun = 500;
+
+	srand(123);
+	for (int64_t n = nmin; n <= nmax; n++) {
+		for (int64_t run = 0; run < nrun; run++)
+			test_case(n, run);
+		err("n = %ld OK", n);
+	}
+}
+
+int
+main(void)
+{
+	test_sort_replace();
+
+	err("OK\n");
+
+	return 0;
+}