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/*----------------------------------------------------------------------------
ADOL-C -- Automatic Differentiation by Overloading in C++
File: sfunc_power.cpp
Revision: $Id$
Contents: function module containing the power example
Each << function module >> contains:
(1) const char* const controlFileName
(2) int indepDim;
(3) void initProblemParameters( void )
(4) void initIndependents( double* indeps )
(5) double originalScalarFunction( double* indeps )
(6) double tapingScalarFunction( int tag, double* indeps )
Copyright (c) Andrea Walther, Andreas Griewank, Andreas Kowarz,
Hristo Mitev, Sebastian Schlenkrich, Jean Utke, Olaf Vogel
This file is part of ADOL-C. This software is provided as open source.
Any use, reproduction, or distribution of the software constitutes
recipient's acceptance of the terms of the accompanying license file.
---------------------------------------------------------------------------*/
#define _SFUNC_POWER_C_
/****************************************************************************/
/* INCLUDES */
#include <adolc/adolc.h>
#include <cstdlib>
#include <time.h>
/****************************************************************************/
/* GLOBAL VARIABLES */
/*--------------------------------------------------------------------------*/
/* Control file name */
const char* controlFileName = "powexam.ctrl";
/*--------------------------------------------------------------------------*/
/* Dimensions */
int indepDim;
/*--------------------------------------------------------------------------*/
/* Other problem dependent parameters */
int exponent;
//static unsigned short int dx[3]; /* variable needed by erand48(.) */
/****************************************************************************/
/* INIT PROBLEM PARAMETERS */
void initProblemParameters( void ) {
fprintf(stdout,"COMPUTATION OF n-th POWER (ADOL-C Example)\n\n");
indepDim = 1;
fprintf(stdout," n = ? ");
fscanf(stdin,"%d",&exponent);
fprintf(stdout,"\n");
/* Init erand48(); */
struct tm s;
time_t t;
time(&t);
s=*localtime(&t);
srand(s.tm_sec*s.tm_min);
/* dx[0]=rand();
dx[1]=rand();
dx[2]=rand();*/
}
/****************************************************************************/
/* INITIALIZE INDEPs */
void initIndependents( double* indeps ) {
indeps[0] = (double)rand();
}
/****************************************************************************/
/* ORIGINAL SCALAR FUNCTION */
/*--------------------------------------------------------------------------*/
/* The recursive determinant function */
double power( double x, int n ) {
double z = 1;
if (n > 0) {
int nh =n/2;
z = power(x,nh);
z *= z;
if (2*nh != n)
z *= x;
return z;
} else
if (n == 0)
return z;
else
return 1.0/power(x,-n);
}
/*--------------------------------------------------------------------------*/
/* The interface function */
double originalScalarFunction( double* indeps ) {
return power(indeps[0],exponent);
}
/****************************************************************************/
/* TAPING SCALAR FUNCTION */
/*--------------------------------------------------------------------------*/
/* The recursive power function */
adouble activePower( adouble x, int n) {
adouble z = 1;
if (n > 0) {
int nh =n/2;
z = activePower(x,nh);
z *= z;
if (2*nh != n)
z *= x;
return z;
} else
if (n == 0)
return z;
else
return 1.0/activePower(x,-n);
}
/*--------------------------------------------------------------------------*/
/* The interface function */
double tapingScalarFunction( int tag, double* indeps ) {
trace_on(tag);
adouble activeIndep;
activeIndep <<= *indeps;
adouble ares = activePower(activeIndep,exponent);
double res = 0;
ares >>= res;
trace_off();
return res;
}
#undef _SFUNC_POWER_C_
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