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/* Implementation of the RANDOM intrinsics

   Copyright 2002, 2004, 2005, 2006, 2007, 2009, 2010

   Free Software Foundation, Inc.

   Contributed by Lars Segerlund <seger@linuxmail.org>

   and Steve Kargl.

This file is part of the GNU Fortran 95 runtime library (libgfortran).

Libgfortran 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 of the License, or (at your option) any later version.

Ligbfortran 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/>.  */

#include "libgfortran.h"

#include <gthr.h>

#include <string.h>

extern void random_r4 (GFC_REAL_4 *);

iexport_proto(random_r4);

extern void random_r8 (GFC_REAL_8 *);

iexport_proto(random_r8);

extern void arandom_r4 (gfc_array_r4 *);

export_proto(arandom_r4);

extern void arandom_r8 (gfc_array_r8 *);

export_proto(arandom_r8);

#ifdef HAVE_GFC_REAL_10

extern void random_r10 (GFC_REAL_10 *);

iexport_proto(random_r10);

extern void arandom_r10 (gfc_array_r10 *);

export_proto(arandom_r10);

#endif

#ifdef HAVE_GFC_REAL_16

extern void random_r16 (GFC_REAL_16 *);

iexport_proto(random_r16);

extern void arandom_r16 (gfc_array_r16 *);

export_proto(arandom_r16);

#endif

#ifdef __GTHREAD_MUTEX_INIT

static __gthread_mutex_t random_lock = __GTHREAD_MUTEX_INIT;

#else

static __gthread_mutex_t random_lock;

#endif

/* Helper routines to map a GFC_UINTEGER_* to the corresponding

   GFC_REAL_* types in the range of [0,1).  If GFC_REAL_*_RADIX are 2

   or 16, respectively, we mask off the bits that don't fit into the

   correct GFC_REAL_*, convert to the real type, then multiply by the

   correct offset.  */

static void

rnumber_4 (GFC_REAL_4 *f, GFC_UINTEGER_4 v)

{

  GFC_UINTEGER_4 mask;

#if GFC_REAL_4_RADIX == 2

  mask = ~ (GFC_UINTEGER_4) 0u << (32 - GFC_REAL_4_DIGITS);

#elif GFC_REAL_4_RADIX == 16

  mask = ~ (GFC_UINTEGER_4) 0u << ((8 - GFC_REAL_4_DIGITS) * 4);

#else

#error "GFC_REAL_4_RADIX has unknown value"

#endif

  v = v & mask;

  *f = (GFC_REAL_4) v * GFC_REAL_4_LITERAL(0x1.p-32);

}

static void

rnumber_8 (GFC_REAL_8 *f, GFC_UINTEGER_8 v)

{

  GFC_UINTEGER_8 mask;

#if GFC_REAL_8_RADIX == 2

  mask = ~ (GFC_UINTEGER_8) 0u << (64 - GFC_REAL_8_DIGITS);

#elif GFC_REAL_8_RADIX == 16

  mask = ~ (GFC_UINTEGER_8) 0u << (16 - GFC_REAL_8_DIGITS) * 4);

#else

#error "GFC_REAL_8_RADIX has unknown value"

#endif

  v = v & mask;

  *f = (GFC_REAL_8) v * GFC_REAL_8_LITERAL(0x1.p-64);

}

#ifdef HAVE_GFC_REAL_10

static void

rnumber_10 (GFC_REAL_10 *f, GFC_UINTEGER_8 v)

{

  GFC_UINTEGER_8 mask;

#if GFC_REAL_10_RADIX == 2

  mask = ~ (GFC_UINTEGER_8) 0u << (64 - GFC_REAL_10_DIGITS);

#elif GFC_REAL_10_RADIX == 16

  mask = ~ (GFC_UINTEGER_10) 0u << ((16 - GFC_REAL_10_DIGITS) * 4);

#else

#error "GFC_REAL_10_RADIX has unknown value"

#endif

  v = v & mask;

  *f = (GFC_REAL_10) v * GFC_REAL_10_LITERAL(0x1.p-64);

}

#endif

#ifdef HAVE_GFC_REAL_16

/* For REAL(KIND=16), we only need to mask off the lower bits.  */

static void

rnumber_16 (GFC_REAL_16 *f, GFC_UINTEGER_8 v1, GFC_UINTEGER_8 v2)

{

  GFC_UINTEGER_8 mask;

#if GFC_REAL_16_RADIX == 2

  mask = ~ (GFC_UINTEGER_8) 0u << (128 - GFC_REAL_16_DIGITS);

#elif GFC_REAL_16_RADIX == 16

  mask = ~ (GFC_UINTEGER_8) 0u << ((32 - GFC_REAL_16_DIGITS) * 4);

#else

#error "GFC_REAL_16_RADIX has unknown value"

#endif

  v2 = v2 & mask;

  *f = (GFC_REAL_16) v1 * GFC_REAL_16_LITERAL(0x1.p-64)

    + (GFC_REAL_16) v2 * GFC_REAL_16_LITERAL(0x1.p-128);

}

#endif

/* libgfortran previously had a Mersenne Twister, taken from the paper:

        Mersenne Twister:       623-dimensionally equidistributed

                                uniform pseudorandom generator.

        by Makoto Matsumoto & Takuji Nishimura

        which appeared in the: ACM Transactions on Modelling and Computer

        Simulations: Special Issue on Uniform Random Number

        Generation. ( Early in 1998 ).

   The Mersenne Twister code was replaced due to

    (1) Simple user specified seeds lead to really bad sequences for

        nearly 100000 random numbers.

    (2) open(), read(), and close() were not properly declared via header

        files.

    (3) The global index i was abused and caused unexpected behavior with

        GET and PUT.

    (4) See PR 15619.

   libgfortran currently uses George Marsaglia's KISS (Keep It Simple Stupid)

   random number generator.  This PRNG combines:

   (1) The congruential generator x(n)=69069*x(n-1)+1327217885 with a period

       of 2^32,

   (2) A 3-shift shift-register generator with a period of 2^32-1,

   (3) Two 16-bit multiply-with-carry generators with a period of

       597273182964842497 > 2^59.

   The overall period exceeds 2^123.

   http://www.ciphersbyritter.com/NEWS4/RANDC.HTM#369F6FCA.74C7C041@stat.fsu.edu

   The above web site has an archive of a newsgroup posting from George

   Marsaglia with the statement:

   Subject: Random numbers for C: Improvements.

   Date: Fri, 15 Jan 1999 11:41:47 -0500

   From: George Marsaglia <geo@stat.fsu.edu>

   Message-ID: <369F6FCA.74C7C041@stat.fsu.edu>

   References: <369B5E30.65A55FD1@stat.fsu.edu>

   Newsgroups: sci.stat.math,sci.math,sci.math.numer-analysis

   Lines: 93

   As I hoped, several suggestions have led to

   improvements in the code for RNG's I proposed for

   use in C. (See the thread "Random numbers for C: Some

   suggestions" in previous postings.) The improved code

   is listed below.

   A question of copyright has also been raised.  Unlike

   DIEHARD, there is no copyright on the code below. You

   are free to use it in any way you want, but you may

   wish to acknowledge the source, as a courtesy.

"There is no copyright on the code below." included the original

KISS algorithm.  */

/* We use three KISS random number generators, with different

   seeds.

   As a matter of Quality of Implementation, the random numbers

   we generate for different REAL kinds, starting from the same

   seed, are always the same up to the precision of these types.

   We do this by using three generators with different seeds, the

   first one always for the most significant bits, the second one

   for bits 33..64 (if present in the REAL kind), and the third one

   (called twice) for REAL(16).  */

#define GFC_SL(k, n)    ((k)^((k)<<(n)))

#define GFC_SR(k, n)    ((k)^((k)>>(n)))

/*   Reference for the seed:

   From: "George Marsaglia" <g...@stat.fsu.edu>

   Newsgroups: sci.math

   Message-ID: <e7CcnWxczriWssCjXTWc3A@comcast.com>

   The KISS RNG uses four seeds, x, y, z, c,

   with 0<=x<2^32, 0<y<2^32, 0<=z<2^32, 0<=c<698769069

   except that the two pairs

   z=0,c=0 and z=2^32-1,c=698769068

   should be avoided.  */

/* Any modifications to the seeds that change kiss_size below need to be

   reflected in check.c (gfc_check_random_seed) to enable correct

   compile-time checking of PUT size for the RANDOM_SEED intrinsic.  */

#define KISS_DEFAULT_SEED_1 123456789, 362436069, 521288629, 316191069

#define KISS_DEFAULT_SEED_2 987654321, 458629013, 582859209, 438195021

#ifdef HAVE_GFC_REAL_16

#define KISS_DEFAULT_SEED_3 573658661, 185639104, 582619469, 296736107

#endif

static GFC_UINTEGER_4 kiss_seed[] = {

  KISS_DEFAULT_SEED_1,

  KISS_DEFAULT_SEED_2,

#ifdef HAVE_GFC_REAL_16

  KISS_DEFAULT_SEED_3

#endif

};

static GFC_UINTEGER_4 kiss_default_seed[] = {

  KISS_DEFAULT_SEED_1,

  KISS_DEFAULT_SEED_2,

#ifdef HAVE_GFC_REAL_16

  KISS_DEFAULT_SEED_3

#endif

};

static const GFC_INTEGER_4 kiss_size = sizeof(kiss_seed)/sizeof(kiss_seed[0]);

static GFC_UINTEGER_4 * const kiss_seed_1 = kiss_seed;

static GFC_UINTEGER_4 * const kiss_seed_2 = kiss_seed + 4;

#ifdef HAVE_GFC_REAL_16

static GFC_UINTEGER_4 * const kiss_seed_3 = kiss_seed + 8;

#endif

/* kiss_random_kernel() returns an integer value in the range of

   (0, GFC_UINTEGER_4_HUGE].  The distribution of pseudorandom numbers

   should be uniform.  */

static GFC_UINTEGER_4

kiss_random_kernel(GFC_UINTEGER_4 * seed)

{

  GFC_UINTEGER_4 kiss;

  seed[0] = 69069 * seed[0] + 1327217885;

  seed[1] = GFC_SL(GFC_SR(GFC_SL(seed[1],13),17),5);

  seed[2] = 18000 * (seed[2] & 65535) + (seed[2] >> 16);

  seed[3] = 30903 * (seed[3] & 65535) + (seed[3] >> 16);

  kiss = seed[0] + seed[1] + (seed[2] << 16) + seed[3];

  return kiss;

}

/*  This function produces a REAL(4) value from the uniform distribution

    with range [0,1).  */

void

random_r4 (GFC_REAL_4 *x)

{

  GFC_UINTEGER_4 kiss;

  __gthread_mutex_lock (&random_lock);

  kiss = kiss_random_kernel (kiss_seed_1);

  rnumber_4 (x, kiss);

  __gthread_mutex_unlock (&random_lock);

}

iexport(random_r4);

/*  This function produces a REAL(8) value from the uniform distribution

    with range [0,1).  */

void

random_r8 (GFC_REAL_8 *x)

{

  GFC_UINTEGER_8 kiss;

  __gthread_mutex_lock (&random_lock);

  kiss = ((GFC_UINTEGER_8) kiss_random_kernel (kiss_seed_1)) << 32;

  kiss += kiss_random_kernel (kiss_seed_2);

  rnumber_8 (x, kiss);

  __gthread_mutex_unlock (&random_lock);

}

iexport(random_r8);

#ifdef HAVE_GFC_REAL_10

/*  This function produces a REAL(10) value from the uniform distribution

    with range [0,1).  */

void

random_r10 (GFC_REAL_10 *x)

{

  GFC_UINTEGER_8 kiss;

  __gthread_mutex_lock (&random_lock);

  kiss = ((GFC_UINTEGER_8) kiss_random_kernel (kiss_seed_1)) << 32;

  kiss += kiss_random_kernel (kiss_seed_2);

  rnumber_10 (x, kiss);

  __gthread_mutex_unlock (&random_lock);

}

iexport(random_r10);

#endif

/*  This function produces a REAL(16) value from the uniform distribution

    with range [0,1).  */

#ifdef HAVE_GFC_REAL_16

void

random_r16 (GFC_REAL_16 *x)

{

  GFC_UINTEGER_8 kiss1, kiss2;

  __gthread_mutex_lock (&random_lock);

  kiss1 = ((GFC_UINTEGER_8) kiss_random_kernel (kiss_seed_1)) << 32;

  kiss1 += kiss_random_kernel (kiss_seed_2);

  kiss2 = ((GFC_UINTEGER_8) kiss_random_kernel (kiss_seed_3)) << 32;

  kiss2 += kiss_random_kernel (kiss_seed_3);

  rnumber_16 (x, kiss1, kiss2);

  __gthread_mutex_unlock (&random_lock);

}

iexport(random_r16);

#endif

/*  This function fills a REAL(4) array with values from the uniform

    distribution with range [0,1).  */

void

arandom_r4 (gfc_array_r4 *x)

{

  index_type count[GFC_MAX_DIMENSIONS];

  index_type extent[GFC_MAX_DIMENSIONS];

  index_type stride[GFC_MAX_DIMENSIONS];

  index_type stride0;

  index_type dim;

  GFC_REAL_4 *dest;

  GFC_UINTEGER_4 kiss;

  int n;

  dest = x->data;

  dim = GFC_DESCRIPTOR_RANK (x);

  for (n = 0; n < dim; n++)

    {

      count[n] = 0;

      stride[n] = GFC_DESCRIPTOR_STRIDE(x,n);

      extent[n] = GFC_DESCRIPTOR_EXTENT(x,n);

      if (extent[n] <= 0)

        return;

    }

  stride0 = stride[0];

  __gthread_mutex_lock (&random_lock);

  while (dest)

    {

      /* random_r4 (dest);  */

      kiss = kiss_random_kernel (kiss_seed_1);

      rnumber_4 (dest, kiss);

      /* Advance to the next element.  */

      dest += stride0;

      count[0]++;

      /* Advance to the next source element.  */

      n = 0;

      while (count[n] == extent[n])

        {

          /* When we get to the end of a dimension, reset it and increment

             the next dimension.  */

          count[n] = 0;

          /* We could precalculate these products, but this is a less

             frequently used path so probably not worth it.  */

          dest -= stride[n] * extent[n];

          n++;

          if (n == dim)

            {

              dest = NULL;

              break;

            }

          else

            {

              count[n]++;

              dest += stride[n];

            }

        }

    }

  __gthread_mutex_unlock (&random_lock);

}

/*  This function fills a REAL(8) array with values from the uniform

    distribution with range [0,1).  */

void

arandom_r8 (gfc_array_r8 *x)

{

  index_type count[GFC_MAX_DIMENSIONS];

  index_type extent[GFC_MAX_DIMENSIONS];

  index_type stride[GFC_MAX_DIMENSIONS];

  index_type stride0;

  index_type dim;

  GFC_REAL_8 *dest;

  GFC_UINTEGER_8 kiss;

  int n;

  dest = x->data;

  dim = GFC_DESCRIPTOR_RANK (x);

  for (n = 0; n < dim; n++)

    {

      count[n] = 0;

      stride[n] = GFC_DESCRIPTOR_STRIDE(x,n);

      extent[n] = GFC_DESCRIPTOR_EXTENT(x,n);

      if (extent[n] <= 0)

        return;

    }

  stride0 = stride[0];

  __gthread_mutex_lock (&random_lock);

  while (dest)

    {

      /* random_r8 (dest);  */

      kiss = ((GFC_UINTEGER_8) kiss_random_kernel (kiss_seed_1)) << 32;

      kiss += kiss_random_kernel (kiss_seed_2);

      rnumber_8 (dest, kiss);

      /* Advance to the next element.  */

      dest += stride0;

      count[0]++;

      /* Advance to the next source element.  */

      n = 0;

      while (count[n] == extent[n])

        {

          /* When we get to the end of a dimension, reset it and increment

             the next dimension.  */

          count[n] = 0;

          /* We could precalculate these products, but this is a less

             frequently used path so probably not worth it.  */

          dest -= stride[n] * extent[n];

          n++;

          if (n == dim)

            {

              dest = NULL;

              break;

            }

          else

            {

              count[n]++;

              dest += stride[n];

            }

        }

    }

  __gthread_mutex_unlock (&random_lock);

}

#ifdef HAVE_GFC_REAL_10

/*  This function fills a REAL(10) array with values from the uniform

    distribution with range [0,1).  */

void

arandom_r10 (gfc_array_r10 *x)

{

  index_type count[GFC_MAX_DIMENSIONS];

  index_type extent[GFC_MAX_DIMENSIONS];

  index_type stride[GFC_MAX_DIMENSIONS];

  index_type stride0;

  index_type dim;

  GFC_REAL_10 *dest;

  GFC_UINTEGER_8 kiss;

  int n;

  dest = x->data;

  dim = GFC_DESCRIPTOR_RANK (x);

  for (n = 0; n < dim; n++)

    {

      count[n] = 0;

      stride[n] = GFC_DESCRIPTOR_STRIDE(x,n);

      extent[n] = GFC_DESCRIPTOR_EXTENT(x,n);

      if (extent[n] <= 0)

        return;

    }

  stride0 = stride[0];

  __gthread_mutex_lock (&random_lock);

  while (dest)

    {

      /* random_r10 (dest);  */

      kiss = ((GFC_UINTEGER_8) kiss_random_kernel (kiss_seed_1)) << 32;

      kiss += kiss_random_kernel (kiss_seed_2);

      rnumber_10 (dest, kiss);

      /* Advance to the next element.  */

      dest += stride0;

      count[0]++;

      /* Advance to the next source element.  */

      n = 0;

      while (count[n] == extent[n])

        {

          /* When we get to the end of a dimension, reset it and increment

             the next dimension.  */

          count[n] = 0;

          /* We could precalculate these products, but this is a less

             frequently used path so probably not worth it.  */

          dest -= stride[n] * extent[n];

          n++;

          if (n == dim)

            {

              dest = NULL;

              break;

            }

          else

            {

              count[n]++;

              dest += stride[n];

            }

        }

    }

  __gthread_mutex_unlock (&random_lock);

}

#endif

#ifdef HAVE_GFC_REAL_16

/*  This function fills a REAL(16) array with values from the uniform

    distribution with range [0,1).  */

void

arandom_r16 (gfc_array_r16 *x)

{

  index_type count[GFC_MAX_DIMENSIONS];

  index_type extent[GFC_MAX_DIMENSIONS];

  index_type stride[GFC_MAX_DIMENSIONS];

  index_type stride0;

  index_type dim;

  GFC_REAL_16 *dest;

  GFC_UINTEGER_8 kiss1, kiss2;

  int n;

  dest = x->data;

  dim = GFC_DESCRIPTOR_RANK (x);

  for (n = 0; n < dim; n++)

    {

      count[n] = 0;

      stride[n] = GFC_DESCRIPTOR_STRIDE(x,n);

      extent[n] = GFC_DESCRIPTOR_EXTENT(x,n);

      if (extent[n] <= 0)

        return;

    }

  stride0 = stride[0];

  __gthread_mutex_lock (&random_lock);

  while (dest)

    {

      /* random_r16 (dest);  */

      kiss1 = ((GFC_UINTEGER_8) kiss_random_kernel (kiss_seed_1)) << 32;

      kiss1 += kiss_random_kernel (kiss_seed_2);

      kiss2 = ((GFC_UINTEGER_8) kiss_random_kernel (kiss_seed_3)) << 32;

      kiss2 += kiss_random_kernel (kiss_seed_3);

      rnumber_16 (dest, kiss1, kiss2);

      /* Advance to the next element.  */

      dest += stride0;

      count[0]++;

      /* Advance to the next source element.  */

      n = 0;

      while (count[n] == extent[n])

        {

          /* When we get to the end of a dimension, reset it and increment

             the next dimension.  */

          count[n] = 0;

          /* We could precalculate these products, but this is a less

             frequently used path so probably not worth it.  */

          dest -= stride[n] * extent[n];

          n++;

          if (n == dim)

            {

              dest = NULL;

              break;

            }

          else

            {

              count[n]++;

              dest += stride[n];

            }

        }

    }

  __gthread_mutex_unlock (&random_lock);

}

#endif

static void

scramble_seed (unsigned char *dest, unsigned char *src, int size)

{

  int i;

  for (i = 0; i < size; i++)

    dest[(i % 2) * (size / 2) + i / 2] = src[i];

}

static void

unscramble_seed (unsigned char *dest, unsigned char *src, int size)

{

  int i;

  for (i = 0; i < size; i++)

    dest[i] = src[(i % 2) * (size / 2) + i / 2];

}

/* random_seed is used to seed the PRNG with either a default

   set of seeds or user specified set of seeds.  random_seed

   must be called with no argument or exactly one argument.  */

void

random_seed_i4 (GFC_INTEGER_4 *size, gfc_array_i4 *put, gfc_array_i4 *get)

{

  int i;

  unsigned char seed[4*kiss_size];

  __gthread_mutex_lock (&random_lock);

  /* Check that we only have one argument present.  */

  if ((size ? 1 : 0) + (put ? 1 : 0) + (get ? 1 : 0) > 1)

    runtime_error ("RANDOM_SEED should have at most one argument present.");

  /* From the standard: "If no argument is present, the processor assigns

     a processor-dependent value to the seed."  */

  if (size == NULL && put == NULL && get == NULL)

      for (i = 0; i < kiss_size; i++)

        kiss_seed[i] = kiss_default_seed[i];

  if (size != NULL)

    *size = kiss_size;

  if (put != NULL)

    {

      /* If the rank of the array is not 1, abort.  */

      if (GFC_DESCRIPTOR_RANK (put) != 1)

        runtime_error ("Array rank of PUT is not 1.");

      /* If the array is too small, abort.  */

      if (GFC_DESCRIPTOR_EXTENT(put,0) < kiss_size)

        runtime_error ("Array size of PUT is too small.");

      /*  We copy the seed given by the user.  */

      for (i = 0; i < kiss_size; i++)

        memcpy (seed + i * sizeof(GFC_UINTEGER_4),

                &(put->data[(kiss_size - 1 - i) * GFC_DESCRIPTOR_STRIDE(put,0)]),

                sizeof(GFC_UINTEGER_4));

      /* We put it after scrambling the bytes, to paper around users who

         provide seeds with quality only in the lower or upper part.  */

      scramble_seed ((unsigned char *) kiss_seed, seed, 4*kiss_size);

    }

  /* Return the seed to GET data.  */

  if (get != NULL)

    {

      /* If the rank of the array is not 1, abort.  */

      if (GFC_DESCRIPTOR_RANK (get) != 1)

        runtime_error ("Array rank of GET is not 1.");