diff --git a/regressions/ck_epoch/validate/Makefile b/regressions/ck_epoch/validate/Makefile
index b7e8567..8e5af7f 100644
--- a/regressions/ck_epoch/validate/Makefile
+++ b/regressions/ck_epoch/validate/Makefile
@@ -1,12 +1,13 @@
 .PHONY: check clean distribution
 
 OBJECTS=ck_stack ck_epoch_synchronize ck_epoch_poll
+HALF=`expr $(CORES) / 2`
 
 all: $(OBJECTS)
 
 check: all
 	./ck_stack $(CORES) 1
-	./ck_epoch_synchronize $(CORES) 1
+	./ck_epoch_synchronize $(HALF) $(HALF) 1
 	./ck_epoch_poll $(CORES) 1
 
 ck_epoch_synchronize: ck_epoch_synchronize.c ../../../include/ck_stack.h ../../../include/ck_epoch.h ../../../src/ck_epoch.c
@@ -22,4 +23,4 @@ clean:
 	rm -rf *~ *.o $(OBJECTS) *.dSYM
 
 include ../../../build/regressions.build
-CFLAGS+=$(PTHREAD_CFLAGS) -D_GNU_SOURCE
+CFLAGS+=$(PTHREAD_CFLAGS) -D_GNU_SOURCE -O0 -g3
diff --git a/regressions/ck_epoch/validate/ck_epoch_synchronize.c b/regressions/ck_epoch/validate/ck_epoch_synchronize.c
index 3aef6c8..e4aea66 100644
--- a/regressions/ck_epoch/validate/ck_epoch_synchronize.c
+++ b/regressions/ck_epoch/validate/ck_epoch_synchronize.c
@@ -45,10 +45,13 @@
 
 #include "../../common.h"
 
+static unsigned int n_rd;
+static unsigned int n_wr;
 static unsigned int n_threads;
 static unsigned int barrier;
 static unsigned int e_barrier;
 static unsigned int readers;
+static unsigned int writers;
 
 #ifndef PAIRS_S
 #define PAIRS_S 10000
@@ -138,10 +141,10 @@ read_thread(void *unused CK_CC_UNUSED)
 }
 
 static void *
-thread(void *unused CK_CC_UNUSED)
+write_thread(void *unused CK_CC_UNUSED)
 {
 	struct node **entry, *e;
-	unsigned int i, j;
+	unsigned int i, j, tid;
 	ck_epoch_record_t record;
 	ck_stack_entry_t *s;
 
@@ -152,6 +155,7 @@ thread(void *unused CK_CC_UNUSED)
 		exit(EXIT_FAILURE);
 	}
 
+	tid = ck_pr_faa_uint(&writers, 1);
 	ck_pr_inc_uint(&barrier);
 	while (ck_pr_load_uint(&barrier) < n_threads);
 
@@ -177,31 +181,38 @@ thread(void *unused CK_CC_UNUSED)
 		while (ck_pr_load_uint(&readers) == 0)
 			ck_pr_stall();
 
-		fprintf(stderr, "\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b[W] %2.2f: %c", (double)j / ITERATE_S, animate[i % strlen(animate)]);
+		if (tid == 0) {
+			fprintf(stderr, "\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b[W] %2.2f: %c",
+			    (double)j / ITERATE_S, animate[i % strlen(animate)]);
+		}
 
 		for (i = 0; i < PAIRS_S; i++) {
+			ck_epoch_begin(&stack_epoch, &record);
 			s = ck_stack_pop_upmc(&stack);
 			e = stack_container(s);
+			ck_epoch_end(&stack_epoch, &record);
 
 			ck_epoch_synchronize(&stack_epoch, &record);
 
 			if (i & 1) {
 				ck_epoch_call(&stack_epoch, &record, &e->epoch_entry, destructor);
 			} else {
-				destructor(&e->epoch_entry);
-			}
+				if (tid == 0 && i % 8192)
+					fprintf(stderr, "\b%c", animate[i % strlen(animate)]);
 
-			if (i % 8192) {
-				fprintf(stderr, "\b%c", animate[i % strlen(animate)]);
+				destructor(&e->epoch_entry);
 			}
 		}
 	}
 
 	ck_epoch_synchronize(&stack_epoch, &record);
-	fprintf(stderr, "\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b[W] Peak: %u (%2.2f%%)\n    Reclamations: %lu\n\n",
+
+	if (tid == 0) {
+		fprintf(stderr, "\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b\b[W] Peak: %u (%2.2f%%)\n    Reclamations: %lu\n\n",
 			record.n_peak,
 			(double)record.n_peak / ((double)PAIRS_S * ITERATE_S) * 100,
 			record.n_dispatch);
+	}
 
 	ck_pr_inc_uint(&e_barrier);
 	while (ck_pr_load_uint(&e_barrier) < n_threads);
@@ -214,23 +225,27 @@ main(int argc, char *argv[])
 	unsigned int i;
 	pthread_t *threads;
 
-	if (argc != 3) {
-		fprintf(stderr, "Usage: stack <threads> <affinity delta>\n");
+	if (argc != 4) {
+		fprintf(stderr, "Usage: stack <#readers> <#writers> <affinity delta>\n");
 		exit(EXIT_FAILURE);
 	}
 
-	n_threads = atoi(argv[1]);
-	a.delta = atoi(argv[2]);
+	n_rd = atoi(argv[1]);
+	n_wr = atoi(argv[2]);
+	n_threads = n_wr + n_rd;
+
+	a.delta = atoi(argv[3]);
 	a.request = 0;
 
 	threads = malloc(sizeof(pthread_t) * n_threads);
-
 	ck_epoch_init(&stack_epoch);
 
-	for (i = 0; i < n_threads - 1; i++)
+	for (i = 0; i < n_rd; i++)
 		pthread_create(threads + i, NULL, read_thread, NULL);
 
-	pthread_create(threads + i, NULL, thread, NULL);
+	do {
+		pthread_create(threads + i, NULL, write_thread, NULL);
+	} while (++i < n_wr + n_rd);
 
 	for (i = 0; i < n_threads; i++)
 		pthread_join(threads[i], NULL);