C++ 中的速度

多次按下 测试运行 (TEST RUN) 按钮，估算这段代码运行 1000 次需要多久。

Start Quiz:

main.cpp robot_functions.cpp robot_functions.h

#include <iostream>
#include "robot_functions.h"  // including the header file

using namespace std;
using std::vector;

// Main function
int main() {
    
    /* Defining the initial beliefs grid:
     [ [0.05f, 0.2f, 0.2f, 0.05f, 0.05f],
       [0.05f, 0.1f, 0.2f, 0.05f, 0.05f] ]
       */
    vector< vector< float > > beliefs_grid; 
    
    // Constructing the row vectors (from arrays)
    float a_row1[] = {0.05f, 0.2f, 0.2f, 0.05f, 0.05f};
    vector<float> vec_row1 (a_row1, a_row1 + sizeof(a_row1) / sizeof(a_row1[0]) );
    float a_row2[] = {0.05f, 0.1f, 0.2f, 0.05f, 0.05f};
    vector<float> vec_row2 (a_row2, a_row2 + sizeof(a_row2) / sizeof(a_row2[0]) );
    // Adding vectors to the beliefs grid
    beliefs_grid.push_back(vec_row1);
    beliefs_grid.push_back(vec_row2);
    
    /* Timing the move function!
     Start the timer below:
     */
    int start_s=clock();
	// Run move 1000 times - move right by 2 each iteration
	// TODO: Change the number of iterations and notice the change in time
	int iterations = 1000;
	
	for(int i = 0; i < iterations; i++){
	    move(0, 2, beliefs_grid, 1.0f);
	}
	// Stop the timer and display the result!
    int stop_s=clock();
    
    cout << "Time to move "<<iterations<<" iterations in milliseconds: " << (stop_s-start_s)/double(CLOCKS_PER_SEC)*1000 << endl;
    
    return 0;   
}

// Contains all functions: move AND helper functions
#include <vector>
#include <iostream>

using namespace std;
using std::vector;

// Normalize and blur helper functions
vector< vector<float> > normalize(vector< vector <float> > grid) {
	float total = 0.0;
	int i;
	int j;
	vector<float> row;
	vector<float> newRow;
	float oldProb;
	for (i = 0; i < grid.size(); i++)
	{
		row = grid[i];
		// cout << "row size: " << row.size(); 
		for (j=0; j< row.size(); j++)
		{
			oldProb = row[j];
			total += oldProb;
		}
	}

	vector< vector<float> > newGrid;

	for (i = 0; i < grid.size(); i++) {
		vector<float> row = grid[i];
		newRow.clear();
		for (j=0; j< row.size(); j++) {
			float oldProb = row[j];
			float newProb = oldProb / total;
			newRow.push_back(newProb);
		}
		newGrid.push_back(newRow);
	}

	return newGrid;
}

vector < vector <float> > blur(vector < vector < float> > grid, float blurring) {

	vector < vector <float> > window;
	vector < vector <float> > newGrid;
	// vector < vector <float> > newGrid = vector(height, vector(width, 0.0) );
	vector <float> row;
	vector <float> newRow;

	int height;
	int width;
	float center, corner, adjacent;

	

	height = grid.size();
	width = grid[0].size();

	center = 1.0 - blurring;
	corner = blurring / 12.0;
	adjacent = blurring / 6.0;

	int i, j;
	float val;

	for (i=0; i<3; i++) {
		row.clear();
		for (j=0; j<3; j++) {
			switch (i) {
				case 0: 
				switch (j) {
					case 0: 
					val = corner;
					break;

					case 1: 
					val = adjacent;
					break;

					case 2: 
					val = corner;
					break;
				}
				break; 

				case 1:
				switch (j) {
					case 0: 
					val = adjacent;
					break;

					case 1: 
					val = center;
					break;
					
					case 2: 
					val = adjacent;
					break;
				}
				break;

				case 2:
				switch(j) {
					case 0: 
					val = corner;
					break;

					case 1: 
					val = adjacent;
					break;
					
					case 2: 
					val = corner;
					break;
				}
				break;
			}
			row.push_back(val);
		}
		window.push_back(row);
	}


	vector <int> DX;
	vector <int> DY;

	DX.push_back(-1); DX.push_back(0); DX.push_back(1);
	DY.push_back(-1); DY.push_back(0); DY.push_back(1);

	int dx;
	int dy;
	int ii;
	int jj;
	int new_i;
	int new_j;
	float multiplier;
	float newVal;

	// initialize new grid to zeros
	for (i=0; i<height; i++) {
		newRow.clear();
		for (j=0; j<width; j++) {
			newRow.push_back(0.0);
		}
		newGrid.push_back(newRow);
	}


	for (i=0; i< height; i++ ) {
		for (j=0; j<width; j++ ) {
			val = grid[i][j];
			newVal = val;
			for (ii=0; ii<3; ii++) {
				dy = DY[ii];
				for (jj=0; jj<3; jj++) {
					dx = DX[jj];
					new_i = (i + dy + height) % height;
					new_j = (j + dx + width) % width;
					multiplier = window[ii][jj];
					newGrid[new_i][new_j] += newVal * multiplier;
				}
			}
		}
	}

	return normalize(newGrid);
}

// Move function defined below -- do not change
vector< vector <float> > move(int dy, int dx, 
	vector < vector <float> > beliefs,
	float blurring) 
{
	int height, width;
	height = beliefs.size();
	width = beliefs[0].size();

	float belief;
	vector < vector <float> > newGrid;
	
	// initialize new grid to zeros
	for (int i=0; i<height; i++) {
	    vector <float> newRow;
		newRow.clear();
		for (int j=0; j<width; j++) {
			newRow.push_back(0.0);
		}
		newGrid.push_back(newRow);
	}

	int new_i, new_j;
	for (int i=0; i<height; i++) {
		for (int j=0; j<width; j++) {
			new_i = (i + dy + height) % height;
			new_j = (j + dx + width)  % width;
			belief = beliefs[i][j];

			newGrid[new_i][new_j] = belief;
		}
	}
	return blur(newGrid, blurring);
}

// This is the header file, which includes function declarations
#include <vector>

// Declare the move function - its return type and parameters
std::vector< std::vector <float> > move(int dy, int dx, 
	std::vector < std::vector <float> > beliefs,
	float blurring);

// Declaring the blur function
std::vector < std::vector <float> > blur(std::vector < std::vector < float> > grid, 
    float blurring);

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