main.cpp File Reference

Main. More...

#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include "defines.h"
#include "CPUtime.h"

Functions
bool	ReadHeightData ()
	Read height data.
void	RecordGradient (double g, int k)
	Record statistics for a gradient.
double	ht (int x, int y)
	Get the height.
void	ProcessSlopeData (int k)
	Process the slope data.
void	SaveSlopeStats ()
	Save slope statistics.
int	main (int argc, char *argv[])
	Main.

Variables
const int	GRIDSIZE = 20
	Number of DEM files on one side of square grid.
const int	CELLSIZE = 4000
	Number of points on one side of a DEM file.
const unsigned int	ARRAYSIZE = CELLSIZE*GRIDSIZE
	Number of points on one side of the whole array of heights.
const int	NUMOCTAVES = 16
	Number of octaves.
const int	MIDOCTAVE = 9
	First octave at which width is greater than height.
const int	GRANULARITY = 50
	Granularity of distribution.
const double	MAXGRADIENT = 1.0
	Maximum gradient sampled.
const double	GRADIENT_DELTA = (double)MAXGRADIENT/GRANULARITY
	Small change in gradient.
const double	GRADIENT_DELTA_INV = 1.0/GRADIENT_DELTA
	Inverse of GRADIENT_DELTA.
double	g_dMaxSlope [NUMOCTAVES]
	Maximum slope in each octave.
double	g_dSumSlope [NUMOCTAVES]
	Sum of slopes in each octave, for computing averages.
long long	g_nPointCount [NUMOCTAVES]
	Number of samples.
long long	g_nDistribution [NUMOCTAVES][GRANULARITY]
	Gradient distribution for each octave.
unsigned char *	g_pHeightBuffer = NULL
	Buffer for packed height data.
unsigned short *	g_nHeight
	Swizzle to access height data by word instead of by byte.
const long long	g_nBufSize
	Size of height buffer.
int	g_nStartTime
	Time that computation began.

Function Documentation

double ht	(	int	x,
		int	y
	)

Get the elevation at a given point.

Parameters

x	X coordinate of point.
y	Y coordinate of point.

Returns

Elevation at (x, y).

int main	(	int	argc,
		char *	argv[]
	)

Does initialization, allocates a honking big block of memory (so you'd better compile this in 64 bit mode, and hopefully you have at least 16GB RAM onboard), reads the data, performs the analysis, saves the results, deallocates the memory and shuts down.

Parameters

argc	Argument count
argv	Arguments.

Returns

0 for success, 1 for failure.

void ProcessSlopeData

(

int

k

)

Process all of the slopes for a given octave.

Parameters

k	The octave number.

bool ReadHeightData

(

)

Read the height data from a packed file UtahDEMData.bin into g_pHeightBuffer, which it assumes points to a buffer of the right size. This data will be accessed automagically through g_nHeight.

Returns

true if it succeeds, false if it fails

void RecordGradient	(	double	g,
		int	k
	)

Add the new gradient to the octave statistics we are gathering.

Parameters

g	A new gradient.
k	The octave from which the gradient was recorded.

void SaveSlopeStats

(

)

Save the gradient statistics to a tab-separated text file output.txt.

Variable Documentation

const long long g_nBufSize

Initial value:

= 
  (long long)ARRAYSIZE * (long long)ARRAYSIZE * (long long)sizeof(short)