/* TO EXERCISE & DISPLAY THE SIGMOID FUNCTION TO BE USED IN NEURAL NETWORKS
   Author: Robert John Morton YE572246C December 1993 */

#include <sys\types.h>
#include <sys\timeb.h>
#include <stdio.h>
#include <graph.h>
#include <math.h>

long	PlotErr[9];


// THE FOLLOWING TWO FUNCTIONS ARE TO BE EXERCISED

short	SigTab[1025];

#define	R		32767
#define	RR		65556	// 65534 + 22

void SigGen(void) {
	int   i;
	for (i = 0; i < 1024; i++)
	    SigTab[i] = (double)(RR / (1 + exp(-((double)(((long)(i)) << 8))/R)) - R);
	SigTab[1024] = R;
}

int Sigmoid(int x) {
	int s, y, j;
	if ((s = x) < 0) x = -x;
	y = *(SigTab + (j = x >> 5));
	y += ((*(SigTab + j + 1) - y) * (x & 0x1F)) >> 5;
	if (s < 0) y = -y;
	return( y );
}


// BELOW IS THE EXERCISER FOR THE TWO FUNCTIONS ABOVE

#define	XYscale	8	// right shift scaling factor
#define	Yorg	174	// origin displacement from top left
#define	Xorg	171	// origin displacement from top left

void ShowScale( short x1, short y1, short x2, short y2 ) {
	_moveto((x1 >> XYscale) + Xorg, (y1 >> XYscale) + Yorg);
	_lineto((x2 >> XYscale) + Xorg, (y2 >> XYscale) + Yorg);
}

double GetTime() {
	struct timeb TimeData;
	ftime(&TimeData);
	return((double)(TimeData.millitm) / 1000 + TimeData.time);
}

main() {
	int x, y, X, Y;
	char far *s;
	double LookTime, ExpTime;
	_setvideomode(_VRES16COLOR);
	_settextposition( 3,19); printf("+32767");
	_settextposition(20,19); printf("-32767");
	_settextposition(11, 3); printf("-32767");
	_settextposition(12,35); printf("+32767");
	_settextposition(1, 1);
	_setcolor(7);
	ShowScale(0, -32767, 0, +32767);
	ShowScale(-32767, 0, +32767, 0);
	printf("SIGMOID FUNCTION FOR USE IN NEURAL NETWORKS");
	_settextposition( 4,46); printf("The SIGMOID formula is:");
	_settextposition( 6,46); printf("f(x) = (2R+d)/(1+exp(-kx)) - R");
	_settextposition( 8,46); printf("Where R = 32767 and");
	_settextposition( 9,46); printf("-32767 <= x <= +32767");
	_settextposition(11,46); printf("`k' determines how step-like the");
	_settextposition(12,46); printf("function becomes. In this test");
	_settextposition(13,46); printf("k = 8. `k' can conveniently be a");
	_settextposition(14,46); printf("multiple of 2: 2,4,8,16,32,64...");
	_settextposition(16,46); printf("`d' is a small adjusting factor");
	_settextposition(17,46); printf("to make f(x) hit 32767 at exactly");
	_settextposition(18,46); printf("the point at which x hits 32767.");
	SigGen();
	_setcolor(9);
	x = -32767;		     // Draw the sigmoid curve
A:	y = Sigmoid(x);
	_setpixel(Xorg + (x >> XYscale), Yorg - (y >> XYscale));
	if (x < 32767) { x++; goto A; }
	_settextposition(24,1);
	printf("CHECKING ACCURACY OF LOOKUP & INTERPOLATION...");
	_settextposition(6,8); printf("Error");
	_setcolor(10);
	x = -32767; Y = 0;
B:	if (x < 0) X = -x; else X = x;
	y = (double)(RR / (1 + exp(-((double)(((long)(X)) << 3))/R)) - R);
	if (x < 0) y = -y;
	_setpixel(Xorg + (x >> XYscale), Yorg - (y >> XYscale));
	y -= Sigmoid(x);
	(PlotErr[y+2])++;
	if(y > Y) Y = y;
	_settextposition(6,14); printf("%2d", y);
	if (x < 32767) { x++; goto B; }
	_settextposition(7, 8); printf("MaxErr%2d",Y);
	_settextposition(20,43); printf("RESULTS:");
	_settextposition(20,53); printf("Error = +2:  %6ld",PlotErr[4]);
	_settextposition(21,53); printf("Error = +1:  %6ld",PlotErr[3]);
	_settextposition(22,53); printf("Error =  0:  %6ld",PlotErr[2]);
	_settextposition(23,53); printf("Error = -1:  %6ld",PlotErr[1]);
	_settextposition(24,53); printf("Error = -2:  %6ld",PlotErr[0]);
	_settextposition(24,1);
	printf("CHECKING SPEED ADVANTAGE...                   ");
	x = -32767;
	ExpTime = GetTime();
C:	if (x < 0) X = -x; else X = x;
	y = (double)(RR / (1 + exp(-((double)(((long)(X)) << 3))/R)) - R);
	if (x < 0) y = -y;
	if (x < 32767) { x++; goto C; }
	ExpTime = GetTime() - ExpTime;
	x = -32767;
	LookTime = GetTime();
D:	y = Sigmoid(x);
	if (x < 32767) { x++; goto D; }
	LookTime = GetTime() - LookTime;
	_settextposition(26,53); printf("Exp(x) Time:  %4.2f", ExpTime);
	_settextposition(27,53); printf("Lookup Time:  %4.2f", LookTime);
	_settextposition(28,53); printf("Speed Ratio:  %4.2f", ExpTime/LookTime);
	_settextposition(24,1);
	printf("FINISHED. HIT `RETURN' TO EXIT.\07");
	_settextposition(26,1);
	getchar();
	_setvideomode(_DEFAULTMODE);
}