exp.cpp

执行EXP计算的快速算法实现源码, Visual C++ 6.0 环境下编译通过.

/* --------------------------------------------------------------
    Test for exponent functions.

    Home page: www.imach.uran.ru/exp

    Copyright 2001-2002 by Dr. Raul N.Shakirov, IMach of RAS(UB).
    All Rights Reserved.

    Permission has been granted to copy, distribute and modify
    software in any context without fee, including a commercial
    application, provided that the aforesaid copyright statement
    is present here as well as exhaustive description of changes.

    THE SOFTWARE IS DISTRIBUTED "AS IS". NO WARRANTY OF ANY KIND
    IS EXPRESSED OR IMPLIED. YOU USE AT YOUR OWN RISK. THE AUTHOR
    WILL NOT BE LIABLE FOR DATA LOSS, DAMAGES, LOSS OF PROFITS OR
    ANY OTHER KIND OF LOSS WHILE USING OR MISUSING THIS SOFTWARE.
-------------------------------------------------------------- */

#include <fstream.h>    /* Header file for standard io functions */
#include <strstrea.h>   /* Header file for standard io functions */
#include <iomanip.h>    /* Header file for standard io functions */
#include <math.h>       /* Header file for standard math functions */
#include "t2exp.h"      /* Header file for t2exp function */
#include "fexp.h"       /* Header file for fexp function */
#include "gettimer.h"   /* Header file for GetTimer() function */

int main (int argc, char **argv)
{
    /*
        Comment out this code if you have changed key values
        of t2exp(), but and have not yet rebuild file t2exp.inl.

        t2expini();
    */

    /*
        To rebuild file t2exp.inl comment out this code, build
        the program and run the program redirecting its output
        to t2exp.inl.

        t2expinl();
        return 0;
    */

    do
    {
       double num = 0;
       if (argc > 1)
       {
           istrstream fin (argv [1]);
           if (!fin) return 1;
           fin >> num;
       }
       else
       {
           cout <<"Please, type argument of exp()"
                   " and press Enter or type Ctrl-C to exit\n";
           cin >> num;
           if (!cin) break;
       }

       #define CYCLES 1000000
       cout << dec << setprecision (15);

       /* Test standard exp() */

       cout << "  exp(" << num << ")=" << flush;
       {
          double expval = 0;
          volatile double arg = num;   /* Prevent optimization */
          long timer = GetTimer (0);
          for (long i = 0; i < CYCLES; i++) expval = exp (arg);
          timer = GetTimer (timer);
          cout << setiosflags (ios::showpoint) <<  expval << " "
               << resetiosflags (ios::showpoint)
               <<"Time=" << setw (6) << timer << " mls" << endl;
       }

       /* Test t2exp() */

       cout << "t2exp(" << num << ")=" << flush;
       {
          double expval = 0;
          volatile double arg = num;   /* Prevent optimization */
          long timer = GetTimer (0);
          for (long i = 0; i < CYCLES; i++) expval = t2exp (arg);
          timer = GetTimer (timer);
          cout << setiosflags (ios::showpoint) <<  expval << " "
               << resetiosflags (ios::showpoint)
               <<"Time=" << setw (6) << timer << " mls" << endl;
       }

       /* Test fexp() */

       cout << " fexp(" << num << ")=" << flush;
       {
          double expval = 0;
          volatile double arg = num;   /* Prevent optimization */
          long timer = GetTimer (0);
          for (long i = 0; i < CYCLES; i++) expval = fexp (arg);
          timer = GetTimer (timer);
          cout << setiosflags (ios::showpoint) <<  expval << " "
               << resetiosflags (ios::showpoint)
               <<"Time=" << setw (6) << timer << " mls" << endl;
       }
    }
    while (argc <= 1);

    return 0;
}