Add libgmp 6.2.0 to third_party
Don't build it yet. That will come in the next review.
Change-Id: Idf3266558165e5ab45f4a41c98cc8c838c8244d5
diff --git a/third_party/gmp/mpz/2fac_ui.c b/third_party/gmp/mpz/2fac_ui.c
new file mode 100644
index 0000000..141a0a7
--- /dev/null
+++ b/third_party/gmp/mpz/2fac_ui.c
@@ -0,0 +1,100 @@
+/* mpz_2fac_ui(RESULT, N) -- Set RESULT to N!!.
+
+Contributed to the GNU project by Marco Bodrato.
+
+Copyright 2012, 2015, 2018 Free Software Foundation, Inc.
+
+This file is part of the GNU MP Library.
+
+The GNU MP Library is free software; you can redistribute it and/or modify
+it under the terms of either:
+
+ * 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.
+
+or
+
+ * the GNU General Public License as published by the Free Software
+ Foundation; either version 2 of the License, or (at your option) any
+ later version.
+
+or both in parallel, as here.
+
+The GNU MP Library 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 General Public License
+for more details.
+
+You should have received copies of the GNU General Public License and the
+GNU Lesser General Public License along with the GNU MP Library. If not,
+see https://www.gnu.org/licenses/. */
+
+#include "gmp-impl.h"
+
+#define FACTOR_LIST_STORE(P, PR, MAX_PR, VEC, I) \
+ do { \
+ if ((PR) > (MAX_PR)) { \
+ (VEC)[(I)++] = (PR); \
+ (PR) = (P); \
+ } else \
+ (PR) *= (P); \
+ } while (0)
+
+#define FAC_2DSC_THRESHOLD ((FAC_DSC_THRESHOLD << 1) | (FAC_DSC_THRESHOLD & 1))
+#define FACTORS_PER_LIMB (GMP_NUMB_BITS / (LOG2C(FAC_2DSC_THRESHOLD-1)+1))
+
+/* Computes n!!, the 2-multi-factorial of n. (aka double-factorial or semi-factorial)
+ WARNING: it assumes that n fits in a limb!
+ */
+void
+mpz_2fac_ui (mpz_ptr x, unsigned long n)
+{
+ ASSERT (n <= GMP_NUMB_MAX);
+
+ if ((n & 1) == 0) { /* n is even, n = 2k, (2k)!! = k! 2^k */
+ mp_limb_t count;
+
+ if ((n <= TABLE_LIMIT_2N_MINUS_POPC_2N) & (n != 0))
+ count = __gmp_fac2cnt_table[n / 2 - 1];
+ else
+ {
+ popc_limb (count, n); /* popc(n) == popc(k) */
+ count = n - count; /* n - popc(n) == k + k - popc(k) */
+ }
+ mpz_oddfac_1 (x, n >> 1, 0);
+ mpz_mul_2exp (x, x, count);
+ } else { /* n is odd */
+ if (n <= ODD_DOUBLEFACTORIAL_TABLE_LIMIT) {
+ MPZ_NEWALLOC (x, 1)[0] = __gmp_odd2fac_table[n >> 1];
+ SIZ (x) = 1;
+ } else if (BELOW_THRESHOLD (n, FAC_2DSC_THRESHOLD)) { /* odd basecase, */
+ mp_limb_t *factors, prod, max_prod;
+ mp_size_t j;
+ TMP_SDECL;
+
+ /* FIXME: we might alloc a fixed amount 1+FAC_2DSC_THRESHOLD/FACTORS_PER_LIMB */
+ TMP_SMARK;
+ factors = TMP_SALLOC_LIMBS (1 + n / (2 * FACTORS_PER_LIMB));
+
+ factors[0] = ODD_DOUBLEFACTORIAL_TABLE_MAX;
+ j = 1;
+ prod = n;
+
+ max_prod = GMP_NUMB_MAX / FAC_2DSC_THRESHOLD;
+ while ((n -= 2) > ODD_DOUBLEFACTORIAL_TABLE_LIMIT)
+ FACTOR_LIST_STORE (n, prod, max_prod, factors, j);
+
+ factors[j++] = prod;
+ mpz_prodlimbs (x, factors, j);
+
+ TMP_SFREE;
+ } else { /* for the asymptotically fast odd case, let oddfac do the job. */
+ mpz_oddfac_1 (x, n, 1);
+ }
+ }
+}
+
+#undef FACTORS_PER_LIMB
+#undef FACTOR_LIST_STORE
+#undef FAC_2DSC_THRESHOLD