Imported gcc-4.4.3

[msp430-gcc.git] / gmp / mpz / bin_uiui.c

diff --git a/gmp/mpz/bin_uiui.c b/gmp/mpz/bin_uiui.c
new file mode 100644 (file)
index 0000000..29bbd60
--- /dev/null
+++ b/gmp/mpz/bin_uiui.c
@@ -0,0 +1,123 @@
+/* mpz_bin_uiui - compute n over k.
+
+Copyright 1998, 1999, 2000, 2001, 2002, 2003, 2006 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 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.
+
+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 Lesser General Public
+License for more details.
+
+You should have received a copy of the GNU Lesser General Public License
+along with the GNU MP Library.  If not, see http://www.gnu.org/licenses/.  */
+
+#include "gmp.h"
+#include "gmp-impl.h"
+#include "longlong.h"
+
+
+/* Enhancement: It ought to be possible to calculate the size of the final
+   result in advance, to a rough approximation at least, and use it to do
+   just one realloc.  Stirling's approximation n! ~= sqrt(2*pi*n)*(n/e)^n
+   (Knuth section 1.2.5) might be of use.  */
+
+/* "inc" in the main loop allocates a chunk more space if not already
+   enough, so as to avoid repeated reallocs.  The final step on the other
+   hand requires only one more limb.  */
+#define MULDIV(inc)                                                     \
+  do {                                                                  \
+    ASSERT (rsize <= ralloc);                                           \
+                                                                        \
+    if (rsize == ralloc)                                                \
+      {                                                                 \
+        mp_size_t  new_ralloc = ralloc + (inc);                         \
+        rp = __GMP_REALLOCATE_FUNC_LIMBS (rp, ralloc, new_ralloc);      \
+        ralloc = new_ralloc;                                            \
+      }                                                                 \
+                                                                        \
+    rp[rsize] = mpn_mul_1 (rp, rp, rsize, nacc);                        \
+    MPN_DIVREM_OR_DIVEXACT_1 (rp, rp, rsize+1, kacc);                   \
+    rsize += (rp[rsize] != 0);                                          \
+                                                                        \
+} while (0)
+
+void
+mpz_bin_uiui (mpz_ptr r, unsigned long int n, unsigned long int k)
+{
+  unsigned long int  i, j;
+  mp_limb_t          nacc, kacc;
+  unsigned long int  cnt;
+  mp_size_t          rsize, ralloc;
+  mp_ptr             rp;
+
+  /* bin(n,k) = 0 if k>n. */
+  if (n < k)
+    {
+      SIZ(r) = 0;
+      return;
+    }
+
+  rp = PTR(r);
+
+  /* Rewrite bin(n,k) as bin(n,n-k) if that is smaller. */
+  k = MIN (k, n-k);
+
+  /* bin(n,0) = 1 */
+  if (k == 0)
+    {
+      SIZ(r) = 1;
+      rp[0] = 1;
+      return;
+    }
+
+  j = n - k + 1;
+  rp[0] = j;
+  rsize = 1;
+  ralloc = ALLOC(r);
+
+  /* Initialize accumulators.  */
+  nacc = 1;
+  kacc = 1;
+
+  for (i = 2; i <= k; i++)
+    {
+      mp_limb_t n1, n0;
+
+      /* Remove common 2 factors.  */
+      cnt = ((nacc | kacc) & 1) ^ 1;
+      nacc >>= cnt;
+      kacc >>= cnt;
+
+      j++;
+      /* Accumulate next multiples.  */
+      umul_ppmm (n1, n0, nacc, (mp_limb_t) j << GMP_NAIL_BITS);
+      n0 >>= GMP_NAIL_BITS;
+      if (n1 == 0)
+        {
+          /* Save new products in accumulators to keep accumulating.  */
+          nacc = n0;
+          kacc = kacc * i;
+        }
+      else
+        {
+          /* Accumulator overflow.  Perform bignum step.  */
+          MULDIV (32);
+          nacc = j;
+          kacc = i;
+        }
+    }
+
+  /* Take care of whatever is left in accumulators.  */
+  MULDIV (1);
+
+  ALLOC(r) = ralloc;
+  SIZ(r) = rsize;
+  PTR(r) = rp;
+}