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ArrayUtil.cpp
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Sat, Aug 24, 02:16

ArrayUtil.cpp
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/*
* ArrayUtil.cpp
*
* Utility functions for using 1D and 2D arrays
*
* Created on: Oct 8, 2012
* Author: Radu Popescu <radu.popescu@epfl.ch>
*/
#include <cassert>
#include <fstream>
#include <iostream>
#include "ArrayUtil.hpp"
/*
* Reads a matrix from a file/. This function handles memory allocation but
* the DeleteMatrix function must be called at the end of the program
*/
void Read(const char *file_name, double **&M, int &n_rows, int &n_cols) {
std::ifstream input_file(file_name, std::ifstream::in);
input_file >> n_rows >> n_cols;
M = new double *[n_rows];
for (int i = 0; i < n_rows; ++i) {
M[i] = new double[n_cols];
for (int j = 0; j < n_cols; ++j) {
input_file >> M[i][j];
}
}
input_file.close();
}
void Read(const char *file_name, double *&v, int &n_elem) {
std::ifstream input_file(file_name, std::ifstream::in);
input_file >> n_elem;
v = new double[n_elem];
for (int i = 0; i < n_elem; ++i) {
input_file >> v[i];
}
input_file.close();
}
// Allocate memory for an n_rows x n_cols matrix
void Allocate(double **&M, const int n_rows, const int n_cols) {
M = new double *[n_rows];
for (int i = 0; i < n_rows; ++i) {
M[i] = new double[n_cols];
}
}
void Allocate(double *&v, const int n_elem) { v = new double[n_elem]; }
// Release memory used by a previously allocated matrix
void Delete(double **&M, const int n_rows) {
for (int i = 0; i < n_rows; ++i) {
delete[] M[i];
}
delete[] M;
}
void Delete(double *&v) { delete[] v; }
// Does matrix multiplication C = A * B ; C must be allocated
void Multiply(double **A, double **B, const double n_rows_A,
const double n_cols_A, const double n_rows_B,
const double n_cols_B, double **&C) {
assert(n_cols_A == n_rows_B);
for (int i = 0; i < n_rows_A; ++i) {
for (int j = 0; j < n_cols_B; ++j) {
C[i][j] = 0;
for (int k = 0; k < n_cols_A; ++k) {
C[i][j] += A[i][k] * B[k][j];
}
}
}
}
// Does matrix multiplication w = v * A; w must be allocated
void Multiply(double *v, double **A, const double n_rows_A,
const double n_cols_A, double *&w) {
for (int i = 0; i < n_cols_A; ++i) {
w[i] = 0;
for (int j = 0; j < n_rows_A; ++j) {
w[i] += v[j] * A[j][i];
}
}
}
// Does matrix multiplication w = A * v; w must be allocated
void Multiply(double **A, double *v, const double n_rows_A,
const double n_cols_A, double *&w) {
for (int i = 0; i < n_rows_A; ++i) {
w[i] = 0;
for (int j = 0; j < n_cols_A; ++j) {
w[i] += v[j] * A[i][j];
}
}
}
// Does matrix multiplication B = A * s ; B must be allocated
void Multiply(double **A, const double s, const double n_rows_A,
const double n_cols_A, double **&B) {
for (int i = 0; i < n_rows_A; ++i) {
for (int j = 0; j < n_cols_A; ++j) {
B[i][j] = A[i][j] * s;
}
}
}
void Print(double **M, const int n_rows, const int n_cols, std::ostream &os) {
for (int i = 0; i < n_rows; ++i) {
for (int j = 0; j < n_cols; ++j) {
os << M[i][j] << " ";
}
os << std::endl;
}
}
void Print(double *v, const int n_elem, std::ostream &os,
const bool transpose) {
if (transpose) {
for (int i = 0; i < n_elem; ++i) {
os << v[i] << std::endl;
}
} else {
for (int i = 0; i < n_elem; ++i) {
os << v[i] << " ";
}
os << std::endl;
}
}

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