Imported gcc-4.4.3

[msp430-gcc.git] / libstdc++-v3 / include / parallel / random_number.h

diff --git a/libstdc++-v3/include/parallel/random_number.h b/libstdc++-v3/include/parallel/random_number.h
new file mode 100644 (file)
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+++ b/libstdc++-v3/include/parallel/random_number.h
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+// -*- C++ -*-
+
+// Copyright (C) 2007, 2008, 2009 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the terms
+// of the GNU General Public License as published by the Free Software
+// Foundation; either version 3, or (at your option) any later
+// version.
+
+// This 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.
+
+// Under Section 7 of GPL version 3, you are granted additional
+// permissions described in the GCC Runtime Library Exception, version
+// 3.1, as published by the Free Software Foundation.
+
+// You should have received a copy of the GNU General Public License and
+// a copy of the GCC Runtime Library Exception along with this program;
+// see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
+// <http://www.gnu.org/licenses/>.
+
+/** @file parallel/random_number.h
+ *  @brief Random number generator based on the Mersenne twister.
+ *  This file is a GNU parallel extension to the Standard C++ Library.
+ */
+
+// Written by Johannes Singler.
+
+#ifndef _GLIBCXX_PARALLEL_RANDOM_NUMBER_H
+#define _GLIBCXX_PARALLEL_RANDOM_NUMBER_H 1
+
+#include <parallel/types.h>
+#include <tr1/random>
+
+namespace __gnu_parallel
+{
+  /** @brief Random number generator, based on the Mersenne twister. */
+  class random_number
+  {
+  private:
+    std::tr1::mt19937  mt;
+    uint64             supremum;
+    uint64             RAND_SUP;
+    double             supremum_reciprocal;
+    double             RAND_SUP_REC;
+
+    // Assumed to be twice as long as the usual random number.
+    uint64             cache;  
+
+    // Bit results.
+    int bits_left;
+    
+    static uint32
+    scale_down(uint64 x,
+#if _GLIBCXX_SCALE_DOWN_FPU
+              uint64 /*supremum*/, double supremum_reciprocal)
+#else
+               uint64 supremum, double /*supremum_reciprocal*/)
+#endif
+       {
+#if _GLIBCXX_SCALE_DOWN_FPU
+         return uint32(x * supremum_reciprocal);
+#else
+         return static_cast<uint32>(x % supremum);
+#endif
+       }
+
+  public:
+    /** @brief Default constructor. Seed with 0. */
+    random_number()
+    : mt(0), supremum(0x100000000ULL),
+      RAND_SUP(1ULL << (sizeof(uint32) * 8)),
+      supremum_reciprocal(double(supremum) / double(RAND_SUP)),
+      RAND_SUP_REC(1.0 / double(RAND_SUP)),
+      cache(0), bits_left(0) { }
+
+    /** @brief Constructor.
+     *  @param seed Random seed.
+     *  @param supremum Generate integer random numbers in the
+     *                  interval @c [0,supremum). */
+    random_number(uint32 seed, uint64 supremum = 0x100000000ULL)
+    : mt(seed), supremum(supremum),
+      RAND_SUP(1ULL << (sizeof(uint32) * 8)),
+      supremum_reciprocal(double(supremum) / double(RAND_SUP)),
+      RAND_SUP_REC(1.0 / double(RAND_SUP)),
+      cache(0), bits_left(0) { }
+
+    /** @brief Generate unsigned random 32-bit integer. */
+    uint32
+    operator()()
+    { return scale_down(mt(), supremum, supremum_reciprocal); }
+
+    /** @brief Generate unsigned random 32-bit integer in the
+       interval @c [0,local_supremum). */
+    uint32
+    operator()(uint64 local_supremum)
+    {
+      return scale_down(mt(), local_supremum,
+                       double(local_supremum * RAND_SUP_REC));
+    }
+
+    /** @brief Generate a number of random bits, run-time parameter.
+     *  @param bits Number of bits to generate. */
+    unsigned long
+    genrand_bits(int bits)
+    {
+      unsigned long res = cache & ((1 << bits) - 1);
+      cache = cache >> bits;
+      bits_left -= bits;
+      if (bits_left < 32)
+       {
+         cache |= ((uint64(mt())) << bits_left);
+         bits_left += 32;
+       }
+      return res;
+    }
+};
+
+} // namespace __gnu_parallel
+
+#endif /* _GLIBCXX_PARALLEL_RANDOM_NUMBER_H */