MNIST Digit Recognition

This program aims to recognize the number 1 from the MNIST dataset. It uses a similarity approach between two matrices and outputs the five closest images.

Files

• X.matrix: the matrix containing the images.
• ones.matrix: the matrix containing the values of the number 1.
• main.c: the source code file.

Functions

Matrix read_matrix(char *filename)

Reads a matrix from a file.

Parameters

• filename: the file containing the matrix.

Return

Returns a matrix structure containing the matrix.

int flat_index(int i, int j, int numcol)

Converts a 2D index to flattened 1D index.

Parameters

• i: the row of the element.
• j: the column of the element.
• numcol: the number of columns.

Return

Returns the flattened index.

int get_elem(Matrix M, int i, int j)

Retrieves an element from a matrix.

Parameters

• M: the matrix.
• i: the row of the element.
• j: the column of the element.

Return

Returns the element at row i and column j.

int * get_row(Matrix M, int i, int j)

Retrieves the pointer to a matrix element.

Parameters

• M: the matrix.
• i: the row of the element.
• j: the column of the element.

Return

Returns the pointer to the element at row i and column j.

void set_elem(Matrix M, int i, int j, int value)

Assigns a value to an element in a matrix.

Parameters

• M: the matrix.
• i: the row of the element.
• j: the column of the element.
• value: the value to be assigned.

void image2char(int image[], int Height, int Width)

Prints an image to the console.

Parameters

• image: an array that stores the flattened image stored in column-major order.
• Height: the height of the image.
• Width: the width of the image.

int dist2(int * a, int * b, int len)

Computes the squared Euclidean distance.

Parameters

• a: an integer array.
• b: an integer array.
• len: the length of the two arrays.

Return

Returns the total squared Euclidean distance.

void pairwise_dist2(Matrix M1, Matrix M2, Matrix D)

Computes the pairwise squared distance of the i-th row of M1 and the j-th row of M2.

Parameters

• M1: the first matrix.
• M2: the second matrix.
• D: a matrix D where D_ij is the squared distance between the i-th row of M1 and the j-th row of M2.

int find_min_index(int a[], int len)

Finds the index of the minimum element in an array.

Parameters

• a: an integer array.
• len: the length of the array.

Return

Returns the index of the minimum element in the array.

void minimum5(int len, int a[], int indices[])

Finds the indices of the 5 minimum elements in an array.

Parameters

• len: the length of the array.
• a: an integer array.
• indices: an