factor: add code to test isqrt() correctness

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 17 insertions, 0 deletions

diff --git a/coreutils/factor.c b/coreutils/factor.c
index 4a131813b..7400174a7 100644
--- a/coreutils/factor.c
+++ b/coreutils/factor.c
@@ -203,6 +203,23 @@ static NOINLINE void factorize(wide_t N)
 int factor_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 int factor_main(int argc UNUSED_PARAM, char **argv)
 {
+#if 0 /* test isqrt() correctness */
+        wide_t n = argv[1] ? bb_strtoull(argv[1], NULL, 0) : time(NULL);
+        for (;;) {
+                half_t h;
+                if (--n == 0)
+                        --n;
+                h = isqrt(n);
+                if (!(n & 0xff))
+                        printf("isqrt(%llx)=%"HALF_FMT"x\n", n, h);
+                if ((wide_t)h * h > n)
+                        return 1;
+                h++;
+                if (h != 0 && (wide_t)h * h <= n)
+                        return 1;
+        }
+#endif
+
         //// coreutils has undocumented option ---debug (three dashes)
         //getopt32(argv, "");
         //argv += optind;