while loop is changing every object and not iterating through - c++

Question

#include <stdio.h>
#include <iostream>
#include "Vector.h"
#include <string.h>
#include <math.h>
#include "Matrix.h"
#include <list>
using namespace std;
// format for a Matrix
char* Matrix::printM(){
char* s = new char[5000*1024];
int i;
for(i=0;i < this->dimension.rows;i++){
int j;
for(j=0;j< this->dimension.columns;j++){
Vector* tmp = this->columns[j];
int x = this->dimension.columns - 1;
if(j == 0){
char buffer[500];
//it0oa(v->coordinate[i],buffer,sizeof(int));
snprintf(buffer,5000,"%f",tmp->coordinate[i]);
strncat(s,"|", 1+ strlen(s));
strncat(s,buffer, strlen(s) + strlen(buffer));
strncat(s,",",strlen(s) + 1);
}else if(j == x){
char buffer[500];
snprintf(buffer,5000,"%f",tmp->coordinate[i]);
strncat(s,buffer,strlen(s) + strlen(buffer));
strncat(s,"|\n",strlen(s)+2);
}else{
char buffer[500];
snprintf(buffer,5000,"%f",tmp->coordinate[i]);
strncat(s,buffer,strlen(s) + strlen(buffer));
strncat(s,",",strlen(s) + 1);
}
}
}
return s;
}
Matrix::Matrix(int di,int de){
this->dimension.rows =de;
this->dimension.columns =di;
this->columns.assign(di,new Vector(de));
}
Matrix::Matrix(std::vector<Vector*> v, int di){
this->dimension.columns = v.size();
this->columns = v;
int it;
this->dimension.rows = v[0]->dimension;
}
Matrix& Matrix::operator+(const Matrix& v){
Matrix* mt = new Matrix(this->dimension.columns,6);
mt->dimension = this->dimension;
int i;
for(i=0;i< mt->dimension.columns;i++){
//mt->columns.push_back(&(*this->columns[i] + *v.columns[i]));
mt->columns[i] = &(*this->columns[i] + *v.columns[i]);
printf("%s\n",mt->columns[0]->printV());
}
return *mt;
}
Matrix& Matrix::operator-(const Matrix& v){
Matrix* mt = new Matrix(this->dimension.columns,7);
mt->dimension = this->dimension;
int i;
for(i=0;i< mt->dimension.columns;i++){
//mt->columns.push_back(&(*this->columns[i] + *v.columns[i]));
mt->columns[i] = &(*this->columns[i] - *v.columns[i]);
printf("%s\n",mt->columns[0]->printV());
}
return *mt;
}
Matrix& Matrix::operator*(const double& v){
Matrix* mt = new Matrix(this->dimension.columns,7);
mt->dimension = this->dimension;
int i;
for(i=0;i< mt->dimension.columns;i++){
//mt->columns.push_back(&(*this->columns[i] + *v.columns[i]));
mt->columns[i] = &(*this->columns[i] * v);
//printf("%s\n",mt->columns[0]->printV());
}
return *mt;
}
std::vector<Vector*> Matrix::row_equiv(Matrix* m){
std::list<Vector*> result;
int i;
for(i=0;i< m->dimension.rows;i++){
std::list<double> lists;
lists.push_back(m->dimension.columns);
int j;
for(j=0;j< m->dimension.columns;j++){
Vector* tmp = m->columns[j];
lists.push_back(tmp->coordinate[i]);
}
j=0;
//std::initializer_list<double> list_h = lists;
Vector* tmp = new Vector(lists);
result.push_back(tmp);
}
std::vector<Vector*> x{std::begin(result),std::end(result)};
return x;
}
Matrix* Matrix::transpose(){
std::vector<Vector*> b = row_equiv(this);
Matrix* mt = new Matrix(b,this->dimension.rows);
return mt;
}
Matrix* Matrix::upperTriangular(){
std::vector<Vector*> tmp = row_equiv(this);
if(this->is_square()){
int j;
for(j=0;j<this->dimension.columns;j++){
double pivot = tmp[j]->coordinate[j];
int i;
for(i=j+1;i<this->dimension.rows;i++){
tmp[i] = &((*tmp[i]) - (*tmp[j] * (tmp[i]->coordinate[j]/pivot)));
}
}
}else if(this->dimension.rows > this->dimension.columns){
//printf("Hello world,\n");
int j;
for(j=0;j<this->dimension.columns;j++){
double pivot = tmp[j]->coordinate[j];
printf("%f\n",pivot);
int i;
for(i=j+1;i< this->dimension.rows;i++){
tmp[i] = &((*tmp[i]) + (*tmp[j] * (tmp[i]->coordinate[j]/-1*pivot)));
printf(" The vector is %s\n",tmp[i]->printV());
}
}
}else if(this->dimension.rows < this->dimension.columns){
printf("Not Hello World!");
}
Matrix* result = new Matrix(tmp,this->dimension.rows);
return result->transpose();
}
// This is supposed to give me the multiplication of matrices but it's not working right now.
Matrix& Matrix::operator*(const Matrix& v){
if(this->dimension.columns == v.dimension.rows){
Matrix* mt = new Matrix(v.dimension.columns,this->dimension.rows);
mt->dimension.rows = this->dimension.rows;
std::vector<Vector*> tmp = row_equiv(this);
std::vector<Vector* > result(v.dimension.columns, new Vector(this->dimension.rows));
for(auto i =0; i < tmp.size();i++){ //for each rows of the first matrix
int j =0;
while(j< this->dimension.columns){ //for each columns of the second matrix
//printf("%f and %f\n",tmp[i]->dimension,this->columns[j]->dimension);
//double x = *tmp[i] * *v.columns[j];
//printf("%f\n",x);
//mt->columns[j]->coordinate[i] = (*tmp[i] * *v.columns[j]); // This line is giving me problems.
//printf("THis is after the code\n");
result[j]->coordinate[i] = (*tmp[i] * *v.columns[j]);
printf("%s and %s %f and %s %s an j = %d\n",tmp[i]->printV(),v.columns[j]->printV(),result[j]->coordinate[i],result[j]->printV(),result[0]->printV(),j);
j++;
}
printf("%s\n",result[0]->printV());
}
return *mt;
}
Matrix* mt = new Matrix(3,2);
return *mt;
}
The problem is with this piece of code
Matrix& Matrix::operator*(const Matrix& v){
if(this->dimension.columns == v.dimension.rows){
Matrix* mt = new Matrix(v.dimension.columns,this->dimension.rows);
mt->dimension.rows = this->dimension.rows;
std::vector<Vector*> tmp = row_equiv(this);
std::vector<Vector* > result(v.dimension.columns, new Vector(this->dimension.rows));
for(auto i =0; i < tmp.size();i++){ //for each rows of the first matrix
int j =0;
while(j< this->dimension.columns){ //for each columns of the second matrix
//printf("%f and %f\n",tmp[i]->dimension,this->columns[j]->dimension);
//double x = *tmp[i] * *v.columns[j];
//printf("%f\n",x);
//mt->columns[j]->coordinate[i] = (*tmp[i] * *v.columns[j]); // This line is giving me problems.
//printf("THis is after the code\n");
result[j]->coordinate[i] = (*tmp[i] * *v.columns[j]);
printf("%s and %s %f and %s %s an j = %d\n",tmp[i]->printV(),v.columns[j]->printV(),result[j]->coordinate[i],result[j]->printV(),result[0]->printV(),j);
j++;
}
printf("%s\n",result[0]->printV());
}
return *mt;
}
Matrix* mt = new Matrix(3,2);
return *mt;
}
The function is supposed to multiply 2 matrices together.
This line is changing result[0] every time it runs and I don't know why. result is a vector of Vector* and the while loop is supposed to iterate through the Vector of the vector(list) and changing the ith component but every time the loop goes through it changes the previous Vector.
result[j]->coordinate[i] = (*tmp[i] * *v.columns[j])
This is the implementation :
for(auto i=0; i < this->dimension.rows;i++){
for(auto j=0; j<v.dimension.columns;j++){
for(auto k=0; k< this->dimension.rows;k++){
result[j]->coordinate[i] += this->columns[i]->coordinate[k] * v.columns[k]->coordinate[j];
printf("j = %d, %s and %s\n",j,result[j]->printV(), result[0]->printV());
}
}
}
When j = 1, result[0] also changes and i don't know why. This is the ouput .
j = 0, <2.000000,0.000000> and <2.000000,0.000000>
j = 0, <2.000000,0.000000> and <2.000000,0.000000>
j = 1, <2.000000,0.000000> and <2.000000,0.000000>
j = 1, <1.000000,0.000000> and <1.000000,0.000000>
j = 2, <1.000000,0.000000> and <1.000000,0.000000>
j = 2, <1.000000,0.000000> and <1.000000,0.000000>
j = 0, <1.000000,-1.000000> and <1.000000,-1.000000>
j = 0, <1.000000,-1.000000> and <1.000000,-1.000000>
j = 1, <1.000000,-1.000000> and <1.000000,-1.000000>
j = 1, <1.000000,1.000000> and <1.000000,1.000000>
j = 2, <1.000000,1.000000> and <1.000000,1.000000>
j = 2, <1.000000,1.000000> and <1.000000,1.000000>

Answer 1

Matrix multiplication is defined differently. It requires 3 nested for loops - not just two:
For every pair (i,j), you need to iterate over all values of k, and do the following pseudocode:
result = zeros(a.rows,b.cols)
for i = 0:a.rows-1
for j = 0:b.cols-1
for k = 0:a.cols-1
result(i,j) += a(i,k) * b(k,j)