diff --git a/main.c b/main.c
index cb63b17..9188133 100644
--- a/main.c
+++ b/main.c
@@ -26,41 +26,47 @@
 #include <sys/mman.h>
 #include <unistd.h>
 
-#define FNAME "puzzles"
-#define FSIZE 729000000U
-#define NSUD (FSIZE / NCELLS)
+#define IFNAME "puzzles"
+#define OFNAME "results"
+#define NSUD 9000000U
+#define FSIZE (NSUD * NCELLS)
 
 int main(void)
 {
-	int fd = open(FNAME, O_RDONLY);
+	int fd;
+
+	fd = open(IFNAME, O_RDONLY);
 	if (fd == -1) {
 		fputs("Failed to open puzzles file\n", stderr);
 		return EXIT_FAILURE;
 	}
+	char *ibuf = mmap(NULL, FSIZE, PROT_READ, MAP_PRIVATE, fd, 0);
+	if (ibuf == MAP_FAILED) {
+		fputs("Failed to mmap() puzzles file\n", stderr);
+		return EXIT_FAILURE;
+	}
+	close(fd);
 
-	char *buf = mmap(NULL, FSIZE, PROT_READ, MAP_PRIVATE, fd, 0);
-	if (buf == MAP_FAILED)
-		fputs("Failed to mmap() puzzle file\n", stderr);
-
+	fd = open(OFNAME, O_RDWR);
+	if (fd == -1) {
+		fputs("Failed to open results file\n", stderr);
+		return EXIT_FAILURE;
+	}
+	char *obuf = mmap(NULL, FSIZE, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
+	if (obuf == MAP_FAILED) {
+		fputs("Failed to mmap() results file\n", stderr);
+		return EXIT_FAILURE;
+	}
 	close(fd);
 
 	struct sudoku sud;
-	unsigned solved = 0;
-	for (unsigned i = 0; i < NSUD; ++i) {
-		if (!load(&sud, buf + (NCELLS * i))) {
-			fputs("Failed to load sudoku\n", stderr);
-			return EXIT_FAILURE;
-		}
-		if (solve(&sud) == -1) {
-			fprintf(stderr, "Solver error on sudoku #%u\n", i);
-			return EXIT_FAILURE;
-		}
-		if (filled(&sud))
-			++solved;
+	for (unsigned o = 0; o < FSIZE; o += NCELLS) {
+		load(&sud, ibuf + o);
+		solve(&sud);
+		save(&sud, obuf + o);
 	}
 
-	double solved_pc = 1e2 * (double)solved / (double)NSUD;
-	printf("Solved %u/%u (%.3lf%%)\n", solved, NSUD, solved_pc);
-
+	munmap(ibuf, FSIZE);
+	munmap(obuf, FSIZE);
 	return EXIT_SUCCESS;
 }
diff --git a/sud.c b/sud.c
index de70cc0..be0ac41 100644
--- a/sud.c
+++ b/sud.c
@@ -48,6 +48,18 @@ bool load(struct sudoku *sud, const char *ptr)
 	return true;
 }
 
+void save(struct sudoku *sud, char *ptr)
+{
+	for (unsigned r = 0; r < NDIGITS; ++r) {
+		for (unsigned c = 0; c < NDIGITS; ++c) {
+			if (DET(sud->cells[r][c]))
+				*ptr++ = '1' + VAL(sud->cells[r][c]);
+			else
+				*ptr++ = '0';
+		}
+	}
+}
+
 enum update_res update(struct sudoku *sud, unsigned r, unsigned c, unsigned val)
 {
 	unsigned tr, tc;
diff --git a/sud.h b/sud.h
index 0718e9f..e9cf138 100644
--- a/sud.h
+++ b/sud.h
@@ -47,6 +47,11 @@ enum check_res { INCOMPLETE, INCORRECT, SOLVED };
  */
 bool load(struct sudoku *sud, const char *ptr);
 
+/**
+ * Write the sudoku to the given pointer (`NCELLS` bytes).
+ */
+void save(struct sudoku *sud, char *ptr);
+
 /**
  * Attempt to update the cell at row `r`, column `c` to have the value
  * `val`. Returns `OK` on success, `ALREADY_DET` if the cell is