clockWC.h

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/**
 * @file clockWC.h
 *    Declarations for a simple class that implements an Ansi C wall clock timer
 *   (see \ref Cantera::clockWC).
 */
/*
 * $Author: hkmoffa $
 * $Revision: 368 $
 * $Date: 2010-01-03 19:46:26 -0500 (Sun, 03 Jan 2010) $
 */
/*
 * Copywrite 2004 Sandia Corporation. Under the terms of Contract
 * DE-AC04-94AL85000 with Sandia Corporation, the U.S. Government
 * retains certain rights in this software.
 * See file License.txt for licensing information.
 */

#ifndef CT_CLOCKWC_H
#define CT_CLOCKWC_H

#include <time.h>
namespace Cantera {

  //! The class provides the wall clock timer in seconds
  /*!
   *  This routine relies on the ANSI C routine, clock(), for
   *  its basic operation. Therefore, it should be fairly 
   *  portable.
   * 
   * The clock will rollover if the calculation is long enough.
   * The wraparound time is roughly 72 minutes for a 32 bit system.
   * This object senses that by seeing if the raw tick counter is
   * has decreased from the last time. If it senses a wraparound has
   * occurred, it increments an internal counter to account for this.
   * Therefore, for long calculations, this object must be called
   * at regular intervals for the seconds timer to be accurate.
   *
   * An example of how to use the timer is given below. timeToDoCalcs
   * countains the wall clock time calculated for the operation.
   * 
   *
   *  @code
   *   clockWC wc;
   *   do_hefty_calculations_atLeastgreaterThanAMillisecond();
   *   double timeToDoCalcs = wc.secondsWC();
   *  @endcode
   *
   *  In general, the process to be timed must take more than a millisecond
   *  for this clock to enough of a significant resolution to be
   *  accurate.
   *
   * @ingroup globalUtilFuncs
   *
   */
  class clockWC {
  public:
    //! Constructor
    /*!
     * This also serves to initialize the ticks within the object
     */
    clockWC();
    
    //! Resets the internal counters and returns the wall clock time
    //! in seconds
    double start();

    //! Returns the wall clock time in seconds since the last reset.
    double secondsWC();

  private: 
    //! Counters the value of the number of ticks from the last call.
    clock_t last_num_ticks;

    //! Number of clock rollovers since the last initialization
    /*!
     * The clock will rollover if the calculation is long enough.
     * This object senses that by seeing if the raw tick counter is
     * has decreased from the last time.
     */
    unsigned int clock_rollovers;

    //! Counter countaining the value of the number of ticks from
    //! the first call (or the reset call).
    clock_t start_ticks;

    //! internal constant containing clock ticks per second
    const  double  inv_clocks_per_sec;

    //! internal constant containing the total number of ticks
    //! per rollover.
    const  double  clock_width;
  };
}
#endif