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Hot Plate

Matriz (2)
I honestly don't know what to do to make this output the information I want it to

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#include <iostream>
#include <iomanip>
#include <string>
#include <fstream>
#include <cmath>

using namespace std;

const int userSize = 10; // 
const double userChange = 0.1;
const double userNeighbors = 4.0;
const int userLeft = 0;
const int userRight = 9;
const int userWidth = 10;
const int decimalPrecision = 4;
string fileName = "Inputplate.txt";

void Initial(double hotPlate[][userSize])
{
	for (int userRow = 0; userRow < userSize; userRow++)
	{
		for (int userCol = 0; userCol < userSize; userCol++)
		{
			if (userRow == userLeft || userRow == userRight)
			{
				if (userCol == userLeft || userCol == userRight)
				{
					hotPlate[userRow][userCol] = 0;
				}
				else
				{
					hotPlate[userRow][userCol] = 100;
				}
			}
			else
			{
				hotPlate[userRow][userCol] = 0;
			}
		}
	}
}

void Print(double hotPlate[][userSize])
{
	for (int userRow = 0; userRow < userSize; userRow++)
	{
		for (int userCol = 0; userCol < userSize; userCol++)
		{
			cout << fixed << setprecision(decimalPrecision) << setw(userWidth) << hotPlate[userRow][userCol];
			if (userCol < userSize - 1) {
				cout << ",";
			}
		}
		cout << endl;
	}
}

void FirstAverage(double hotPlate[][userSize], double copyHotplate[][userSize])
{

	double averageTemp = 0.0;
	int userRow = 0;
	int userCol = 0;

	for (int userRow = 1; userRow < userSize - 1; userRow++)
	{
		for (int userCol = 1; userCol < userSize - 1; userCol++)
		{
			averageTemp = (hotPlate[userRow - 1][userCol] + hotPlate[userRow + 1][userCol] + hotPlate[userRow][userCol - 1] + hotPlate[userRow][userCol + 1]) / userNeighbors;
			copyHotplate[userRow][userCol] = averageTemp;

		}

	}




}


void MyAverage(double hotPlate[][userSize], double copyHotplate[][userSize]) {

	bool keepGoing = false;
	const double userChange = 0.1;
	const double userNeighbors = 4.0;

	do {
		keepGoing = false;
		for (int userRow = 1; userRow < userSize - 1; userRow++) {
			for (int userColumn = 1; userColumn < userSize - 1; userColumn++) {

				copyHotplate[userRow][userColumn] = (hotPlate[userRow + 1][userColumn] + hotPlate[userRow - 1][userColumn] + hotPlate[userRow][userColumn + 1] + hotPlate[userRow][userColumn - 1]) / userNeighbors;
				if (abs(hotPlate[userRow][userColumn] - copyHotplate[userRow][userColumn]) > userChange) {
					keepGoing = true;
				}
			}
		}
		for (int userRow = 1; userRow < userSize - 1; userRow++) {
			for (int column = 1; column < userSize - 1; column++) {
				hotPlate[userRow][column] = copyHotplate[userRow][column];
			}
		}
	} while (keepGoing);

}

void SaveFile(double hot_plate[][userSize])
{
	ofstream out;
	out.open("Hotplate.csv");

	for (int userRow = 0; userRow < userSize; userRow++)
	{
		for (int userCol = 0; userCol < userSize; userCol++)
		{
			out << fixed << fixed << setprecision(decimalPrecision) << setw(userWidth) << hot_plate[userRow][userCol];
			if (userCol < userSize - 1) {
				out << ",";
			}


		}
		out << endl;

	}

	out.close();
}

int main()
{
	double hotPlate[userSize][userSize];
	double copyHotplate[userSize][userSize];
	bool keepGoing = false;
	const double userChange = 0.1;
	const double userNeighbors = 4.0;

	cout << "Hotplate simulator" << endl << endl;
	cout << "Printing initial plate..." << endl;
	Initial(hotPlate);
	Initial(copyHotplate);
	Print(hotPlate);

	cout << endl << endl;

	cout << "Printing plate after one iteration..." << endl;
	FirstAverage(hotPlate, copyHotplate);
	Print(copyHotplate);

	cout << endl << endl;

	cout << "Printing final plate..." << endl;
	MyAverage(hotPlate, copyHotplate);
	Print(hotPlate);

	cout << endl << "Outputting final plate to file \"Hotplate.csv\"" << endl;
	SaveFile(hotPlate);

	ifstream in;
	in.open(fileName);

	cout << endl << "Printing input plate after 3 updates..." << endl;
	for (int k = 1; k < 3; k++) {
		keepGoing = false;
		for (int row = 1; row < userSize - 1; row++) {
			for (int column = 1; column < userSize - 1; column++) {

				copyHotplate[row][column] = (hotPlate[row + 1][column] + hotPlate[row - 1][column] + hotPlate[row][column + 1] + hotPlate[row][column - 1]) / userNeighbors;
				if (abs(hotPlate[row][column] - copyHotplate[row][column]) > userChange) {
					keepGoing = true;
				}
			}
			for (int row = 1; row < userSize - 1; row++) {
				for (int column = 1; column < userSize - 1; column++) {
					hotPlate[row][column] = copyHotplate[row][column];
				}
			}
			Print(copyHotplate);
		}
	}

	return 0;
}


This is how the output should look...

Hotplate simulator

Printing initial plate...
    0.000,  100.000,  100.000,  100.000,    0.000
    0.000,    0.000,    0.000,    0.000,    0.000
    0.000,    0.000,    0.000,    0.000,    0.000
    0.000,    0.000,    0.000,    0.000,    0.000
    0.000,  100.000,  100.000,  100.000,    0.000

Printing plate after one iteration...
    0.000,  100.000,  100.000,  100.000,    0.000
    0.000,   25.000,   25.000,   25.000,    0.000
    0.000,    0.000,    0.000,    0.000,    0.000
    0.000,   25.000,   25.000,   25.000,    0.000
    0.000,  100.000,  100.000,  100.000,    0.000

Printing final plate...
    0.000,  100.000,  100.000,  100.000,    0.000
    0.000,   49.854,   62.305,   49.854,    0.000
    0.000,   37.305,   49.707,   37.305,    0.000
    0.000,   49.854,   62.305,   49.854,    0.000
    0.000,  100.000,  100.000,  100.000,    0.000

Outputting final plate to file "Hotplate.csv"...

Printing input plate after 3 updates...
    0.000,  100.000,  100.000,  100.000,    0.000
    0.000,   -2.853,   62.304,  -49.853,    0.000
    0.000,   37.304,   49.707,   37.304,    0.000
    0.000,   49.853,   -2.304,    1.853,    0.000
    0.000,  100.000,  100.000,  100.000,    0.000


And this is how it shows up instead... 

Hotplate simulator

Printing initial plate...
    0.0000,  100.0000,  100.0000,  100.0000,  100.0000,  100.0000,  100.0000,  100.0000,  100.0000,    0.0000
    0.0000,    0.0000,    0.0000,    0.0000,    0.0000,    0.0000,    0.0000,    0.0000,    0.0000,    0.0000
    0.0000,    0.0000,    0.0000,    0.0000,    0.0000,    0.0000,    0.0000,    0.0000,    0.0000,    0.0000
    0.0000,    0.0000,    0.0000,    0.0000,    0.0000,    0.0000,    0.0000,    0.0000,    0.0000,    0.0000
    0.0000,    0.0000,    0.0000,    0.0000,    0.0000,    0.0000,    0.0000,    0.0000,    0.0000,    0.0000
    0.0000,    0.0000,    0.0000,    0.0000,    0.0000,    0.0000,    0.0000,    0.0000,    0.0000,    0.0000
    0.0000,    0.0000,    0.0000,    0.0000,    0.0000,    0.0000,    0.0000,    0.0000,    0.0000,    0.0000
    0.0000,    0.0000,    0.0000,    0.0000,    0.0000,    0.0000,    0.0000,    0.0000,    0.0000,    0.0000
    0.0000,    0.0000,    0.0000,    0.0000,    0.0000,    0.0000,    0.0000,    0.0000,    0.0000,    0.0000
    0.0000,  100.0000,  100.0000,  100.0000,  100.0000,  100.0000,  100.0000,  100.0000,  100.0000,    0.0000
MikeyBoy (5631)
Duplicate of:

http://www.cplusplus.com/forum/general/239965/

Please DON'T post multiple threads for the same question.
icy1 (596)
@Matriz, do you want to maybe explain what your structures are, your iteration method and reasons for the "keepGoing" ? What's in your "inputplate" file ?

As it stands, your question is basically, "Here, look. Fix?"

Edit: also, having identical variable names both in global and local scope isn't helping anyone.
Last edited on
lastchance (6980)
Google "steady-state temperature distribution rectangular plate" or, possibly, "Laplace equation".

For this particular problem, every node should end up as the average of the 4 nodes surrounding it,
Ti,j=(Ti-1,j+Ti+1,j+Ti,j-1+Ti,j+1)/4
apart from the boundary conditions which are here set as 0 and 100.

It looks like the iteration method is either Jacobi method (RHS uses values from the end of the last complete iteration; requires a copy first):
http://mathworld.wolfram.com/JacobiMethod.html
or Gauss-Seidel (RHS uses the latest updated value)
http://mathworld.wolfram.com/Gauss-SeidelMethod.html
(This code appears to be an unholy mix of the two.)

In the model answer:
Printing input plate after 3 updates...
    0.000,  100.000,  100.000,  100.000,    0.000
    0.000,   -2.853,   62.304,  -49.853,    0.000

there is absolutely no way of getting those negatives, even for early iterations, so some of your specification is wrong.


"keepGoing" if change at any node on this iteration is greater than some tolerance, userChange=0.1 (This is a tad large).
Last edited on
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