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diff --git a/libgfortran/intrinsics/rand.c b/libgfortran/intrinsics/rand.c
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+++ b/libgfortran/intrinsics/rand.c
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+/* Implementation of the IRAND, RAND, and SRAND intrinsics.
+   Copyright (C) 2004, 2005, 2007, 2009 Free Software Foundation, Inc.
+   Contributed by Steven G. Kargl <kargls@comcast.net>.
+
+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.
+
+Libgfortran 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/>.  */
+
+/* Simple multiplicative congruent algorithm.
+   The period of this generator is approximately 2^31-1, which means that
+   it should not be used for anything serious.  The implementation here
+   is based of an algorithm from  S.K. Park and K.W. Miller, Comm. ACM,
+   31, 1192-1201 (1988).  It is also provided solely for compatibility 
+   with G77.  */
+
+#include "libgfortran.h"
+#include <gthr.h>
+
+#define GFC_RAND_A	16807
+#define GFC_RAND_M	2147483647
+#define GFC_RAND_M1	(GFC_RAND_M - 1)
+
+static GFC_UINTEGER_8 rand_seed = 1;
+#ifdef __GTHREAD_MUTEX_INIT
+static __gthread_mutex_t rand_seed_lock = __GTHREAD_MUTEX_INIT;
+#else
+static __gthread_mutex_t rand_seed_lock;
+#endif
+
+
+/* Set the seed of the irand generator.  Note 0 is a bad seed.  */
+
+static void
+srand_internal (GFC_INTEGER_8 i)
+{
+  rand_seed = i ? i : 123459876;
+}
+
+extern void PREFIX(srand) (GFC_INTEGER_4 *i);
+export_proto_np(PREFIX(srand));
+
+void
+PREFIX(srand) (GFC_INTEGER_4 *i)
+{
+  __gthread_mutex_lock (&rand_seed_lock);
+  srand_internal (*i);
+  __gthread_mutex_unlock (&rand_seed_lock);
+}
+
+/* Return an INTEGER in the range [1,GFC_RAND_M-1].  */
+
+extern GFC_INTEGER_4 irand (GFC_INTEGER_4 *);
+iexport_proto(irand);
+
+GFC_INTEGER_4
+irand (GFC_INTEGER_4 *i)
+{
+  GFC_INTEGER_4 j;
+  if (i)
+    j = *i;
+  else
+    j = 0;
+
+  __gthread_mutex_lock (&rand_seed_lock);
+
+  switch (j)
+  {
+    /* Return the next RN. */
+    case 0:
+      break;
+
+    /* Reset the RN sequence to system-dependent sequence and return the
+       first value.  */
+    case 1:
+      srand_internal (0);
+      break;
+    
+    /* Seed the RN sequence with j and return the first value.  */
+    default:
+      srand_internal (j);
+      break;
+   }
+
+   rand_seed = GFC_RAND_A * rand_seed % GFC_RAND_M;
+   j = (GFC_INTEGER_4) rand_seed;
+
+  __gthread_mutex_unlock (&rand_seed_lock);
+
+   return j;
+}
+iexport(irand);
+
+
+/*  Return a random REAL in the range [0,1).  */
+
+extern GFC_REAL_4 PREFIX(rand) (GFC_INTEGER_4 *i);
+export_proto_np(PREFIX(rand));
+
+GFC_REAL_4
+PREFIX(rand) (GFC_INTEGER_4 *i)
+{
+  GFC_UINTEGER_4 mask;
+#if GFC_REAL_4_RADIX == 2
+  mask = ~ (GFC_UINTEGER_4) 0u << (32 - GFC_REAL_4_DIGITS + 1);
+#elif GFC_REAL_4_RADIX == 16
+  mask = ~ (GFC_UINTEGER_4) 0u << ((8 - GFC_REAL_4_DIGITS) * 4 + 1);
+#else
+#error "GFC_REAL_4_RADIX has unknown value"
+#endif
+  return ((GFC_UINTEGER_4) (irand(i) -1) & mask) * (GFC_REAL_4) 0x1.p-31f;
+}
+
+#ifndef __GTHREAD_MUTEX_INIT
+static void __attribute__((constructor))
+init (void)
+{
+  __GTHREAD_MUTEX_INIT_FUNCTION (&rand_seed_lock);
+}
+#endif