source: CIVL/examples/mpi-omp/AMG2013/utilities/binsearch.c

/*BHEADER**********************************************************************
 * Copyright (c) 2008,  Lawrence Livermore National Security, LLC.
 * Produced at the Lawrence Livermore National Laboratory.
 * This file is part of HYPRE.  See file COPYRIGHT for details.
 *
 * HYPRE 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) version 2.1 dated February 1999.
 *
 * $Revision: 2.4 $
 ***********************************************************************EHEADER*/

 
#include "utilities.h"
 
/*--------------------------------------------------------------------------
 * hypre_BinarySearch
 * to contain ordered nonnegative numbers
 * the routine returns the location of the value or -1
 *--------------------------------------------------------------------------*/
 
int hypre_BinarySearch(int *list, int value, int list_length)
{
   int low, high, m;
   int not_found = 1;

   low = 0;
   high = list_length-1; 
   while (not_found && low <= high)
   {
      m = (low + high) / 2;
      if (value < list[m])
      {
         high = m - 1;
      }
      else if (value > list[m])
      {
        low = m + 1;
      }
      else
      {
        not_found = 0;
        return m;
      }
   }
   return -1;
}

/*--------------------------------------------------------------------------
 * hypre_BigBinarySearch
 * to contain ordered nonnegative numbers
 * the routine returns the location of the value or -1
 *--------------------------------------------------------------------------*/
 
int hypre_BigBinarySearch(HYPRE_BigInt *list, HYPRE_BigInt value, int list_length)
{
   int low, high, m;
   int not_found = 1;

   low = 0;
   high = list_length-1; 
   while (not_found && low <= high)
   {
      m = (low + high) / 2;
      if (value < list[m])
      {
         high = m - 1;
      }
      else if (value > list[m])
      {
        low = m + 1;
      }
      else
      {
        not_found = 0;
        return m;
      }
   }
   return -1;
}