1 files changed, 64 insertions, 0 deletions
diff --git a/tests/trootofunity.c b/tests/trootofunity.c
new file mode 100644
index 0000000..7ac1c3d
--- /dev/null
+++ b/tests/trootofunity.c
@@ -0,0 +1,64 @@
+/* ttan -- test file for mpc_rootofunity.
+
+Copyright (C) 2012 INRIA
+
+This file is part of GNU MPC.
+
+GNU MPC is free software; you can redistribute it and/or modify it under
+the terms of the GNU Lesser General Public License as published by the
+Free Software Foundation; either version 3 of the License, or (at your
+option) any later version.
+
+GNU MPC is distributed in the hope that it will be useful, but WITHOUT ANY
+WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for
+more details.
+
+You should have received a copy of the GNU Lesser General Public License
+along with this program. If not, see http://www.gnu.org/licenses/ .
+*/
+
+#include "mpc-tests.h"
+
+static void
+check (unsigned long int n)
+   /* checks whether zeta_n^n = 1, which is somewhat dangerous in floating
+      point                                                                */
+{
+   mpc_t z, zero;
+   mpfr_prec_t prec;
+
+   mpc_init2 (z, 2);
+   mpc_init2 (zero, 2);
+
+   for (prec = 2*n; prec < 1000; prec = (mpfr_prec_t) (prec * 1.1 + 1)) {
+      mpc_set_prec (z, prec);
+      mpc_set_prec (zero, prec);
+
+      mpc_rootofunity (z, n, MPC_RNDNN);
+      mpc_pow_ui (zero, z, n, MPC_RNDNN);
+      mpc_sub_ui (zero, zero, 1u, MPC_RNDNN);
+      if (MPC_MAX (mpfr_get_exp (mpc_realref (zero)), mpfr_get_exp (mpc_imagref (zero)))
+          > - (prec - n)) {
+         fprintf (stderr, "rootofunity too imprecise for n=%lu\n", n);
+         MPC_OUT (z);
+         MPC_OUT (zero);
+         exit (1);
+      }
+   }
+
+   mpc_clear (z);
+   mpc_clear (zero);
+}
+
+
+int
+main (void)
+{
+   int n;
+
+   for (n = 1; n < 10000; n += 10)
+      check (n);
+   
+   return 0;
+}