diff --git a/serial/Makefile b/serial/Makefile
index 78d2e2e..a6ed4bc 100644
--- a/serial/Makefile
+++ b/serial/Makefile
@@ -7,8 +7,8 @@ CC = gcc
 RM = rm -f
 CFLAGS_DEBUG=-O0 -g -I.
 CFLAGS=-O3 -I.
-OBJ=serial_gs_pagerank.o serial_gs_pagerank_functions.o
-DEPS=serial_gs_pagerank_functions.h
+OBJ=serial_gs_pagerank.o serial_gs_pagerank_functions.o sparse_matrix.o
+DEPS=serial_gs_pagerank_functions.h sparse_matrix.h
 
 # ==========================================
 # TARGETS
diff --git a/serial/serial_gs_pagerank.c b/serial/serial_gs_pagerank.c
index 5b056b9..355915f 100644
--- a/serial/serial_gs_pagerank.c
+++ b/serial/serial_gs_pagerank.c
@@ -1,18 +1,21 @@
 #include <sys/time.h>
 
 #include "serial_gs_pagerank_functions.h"
+#include "sparse_matrix.h"
 
 struct timeval startwtime, endwtime;
 double seq_time;
 
 int main(int argc, char **argv) {
-	int **directedWebGraph;
-	double **transitionMatrix, *pagerankVector;
+	SparseMatrix transitionMatrix;
+	double *pagerankVector;
 	Parameters parameters;
 
+	transitionMatrix = createSparseMatrix();
+
 	parseArguments(argc, argv, &parameters);
 
-	initialize(&directedWebGraph, &transitionMatrix, &pagerankVector, &parameters);
+	initialize(&transitionMatrix, &pagerankVector, &parameters);
 
 	// Starts wall-clock timer
 	gettimeofday (&startwtime, NULL);
diff --git a/serial/serial_gs_pagerank_functions.c b/serial/serial_gs_pagerank_functions.c
index 88d6d4d..99ef587 100644
--- a/serial/serial_gs_pagerank_functions.c
+++ b/serial/serial_gs_pagerank_functions.c
@@ -9,10 +9,11 @@ const char *ARGUMENT_OUTPUT_FILENAME = "-o";
 
 const int NUMERICAL_BASE = 10;
 char *DEFAULT_OUTPUT_FILENAME = "pagerank_output";
+const int MAX_PAGE_LINKS_TEXT_SIZE = 4096;
 
 // ==================== PAGERANK ====================
 
-int pagerank(double ***transitionMatrix, double **pagerankVector, Parameters parameters) {
+int pagerank(SparseMatrix *transitionMatrix, double **pagerankVector, Parameters parameters) {
 	int iterations = 0;
 	double delta,
 	*vectorDifference = (double *) malloc(parameters.numberOfPages * sizeof(double)),
@@ -40,10 +41,13 @@ int pagerank(double ***transitionMatrix, double **pagerankVector, Parameters par
 	do {
 		memcpy(previousPagerankVector, *pagerankVector, parameters.numberOfPages * sizeof(double));
 
-		matrixVectorMultiplication(*transitionMatrix, previousPagerankVector,
-			linksFromConvergedPagesPagerankVector, convergedPagerankVector,
+		matrixVectorMultiplication(transitionMatrix, previousPagerankVector,
 			pagerankVector, parameters.numberOfPages, parameters.dampingFactor);
 
+		for (int i=0; i<parameters.numberOfPages; ++i) {
+			(*pagerankVector)[i] += linksFromConvergedPagesPagerankVector[i] + convergedPagerankVector[i];
+		}
+
 		if (parameters.history) {
 			savePagerankToFile(parameters.outputFilename, iterations != 0,
 				*pagerankVector, parameters.numberOfPages);
@@ -54,7 +58,7 @@ int pagerank(double ***transitionMatrix, double **pagerankVector, Parameters par
 		}
 		delta = vectorNorm(vectorDifference, parameters.numberOfPages);
 
-		if (!iterations % 10) {
+		if (iterations && !iterations % 10) {
 			for (int i=0; i<parameters.numberOfPages; ++i) {
 				double temp = fabs((*pagerankVector)[i] - previousPagerankVector[i]) / fabs(previousPagerankVector[i]);
 				if (temp < parameters.convergenceCriterion){
@@ -67,12 +71,11 @@ int pagerank(double ***transitionMatrix, double **pagerankVector, Parameters par
 				if (converganceMatrix[i] == true) {
 					for (int j=0; j<parameters.numberOfPages; ++j){
 						if (converganceMatrix[j] == false){
-							linksFromConvergedPages[i][j] = (*transitionMatrix)[i][j];
+							SparseMatrixElement *element = getElement(*transitionMatrix, i, j);
+							linksFromConvergedPages[i][j] = element != NULL ? element->value : 0;
 						}
-						// Zeros out CN and CC sub-matrices
-						(*transitionMatrix)[i][j] = 0;
-						// Zeros out NC sub-matrix
-						(*transitionMatrix)[j][i] = 0;
+						deleteElement(transitionMatrix, i, j);
+						deleteElement(transitionMatrix, j, i);
 					}
 
 					double sum = 0;
@@ -104,14 +107,14 @@ int pagerank(double ***transitionMatrix, double **pagerankVector, Parameters par
  * from the file and creates the initial transition probability distribution
  * matrix.
 */
-void initialize(int ***directedWebGraph, double ***transitionMatrix,
+void initialize(SparseMatrix *transitionMatrix,
 	double **pagerankVector, Parameters *parameters) {
 
 	// Reads web graph from file
 	if ((*parameters).verbose) {
 		printf("----- Reading graph from file -----\n");
 	}
-	readGraphFromFile(directedWebGraph, parameters);
+	generateNormalizedTransitionMatrixFromFile(transitionMatrix, parameters);
 
 	// Outputs the algorithm parameters to the console
 	if ((*parameters).verbose) {
@@ -135,49 +138,8 @@ void initialize(int ***directedWebGraph, double ***transitionMatrix,
 		(*pagerankVector)[i] = webUniformProbability;
 	}
 
-	// Generates the initial transition matrix (matrix P).
-	generateNormalizedTransitionMatrix(transitionMatrix, *directedWebGraph, *parameters);
 	// Transposes the transition matrix (P^T).
-	transposeMatrix(transitionMatrix, (*parameters).numberOfPages, (*parameters).numberOfPages);
-}
-
-/*
- * generateNormalizedTransitionMatrix generates the normalized transition matrix
- * from the graph data (matrix P').
-*/
-void generateNormalizedTransitionMatrix(double ***transitionMatrix,
-	int **directedWebGraph, Parameters parameters) {
-	// Allocates memory for the transitionMatrix rows
-	(*transitionMatrix) = (double **) malloc(parameters.numberOfPages * sizeof(double *));
-
-	for (int i=0; i<parameters.numberOfPages; ++i) {
-		// Allocates memory for this row's columns
-		(*transitionMatrix)[i] = (double *) malloc(parameters.numberOfPages * sizeof(double));
-
-		// Calculates the outdegree of this page
-		int pageOutdegree = 0;
-		for (int j=0; j<parameters.numberOfPages; ++j) {
-			pageOutdegree += directedWebGraph[i][j];
-		}
-
-		// Populates this row of the transition matrix
-		if (pageOutdegree != 0) {
-			// Calculates the uniform probability once.
-			double pageUniformProbability = 1. / pageOutdegree;
-
-			for (int j=0; j<parameters.numberOfPages; ++j) {
-				if (directedWebGraph[i][j] == 1){
-					(*transitionMatrix)[i][j] = pageUniformProbability;
-				} else {
-					(*transitionMatrix)[i][j] = 0;
-				}
-			}
-		} else {
-			for (int j=0; j<parameters.numberOfPages; ++j) {
-				(*transitionMatrix)[i][j] = 0;
-			}
-		}
-	}
+	transposeSparseMatrix(transitionMatrix);
 }
 
 // ==================== MATH UTILS ====================
@@ -186,26 +148,22 @@ void generateNormalizedTransitionMatrix(double ***transitionMatrix,
  * matrixVectorMultiplication calculates the product of the multiplication
  * between a matrix and the a vector in a cheap way.
 */
-void matrixVectorMultiplication(double **transitionMatrix, double *previousPagerankVector,
-	double *linksFromConvergedPagesPagerankVector, double *convergedPagerankVector,
+void matrixVectorMultiplication(SparseMatrix *transitionMatrix, double *previousPagerankVector,
 	double **pagerankVector, int vectorSize, double dampingFactor) {
 	double webUniformProbability = 1. / vectorSize;
 
-	for (int i=0; i<vectorSize; ++i) {
-		double sum = 0;
+	sparseMatrixVectorMultiplication(*transitionMatrix, previousPagerankVector,
+		pagerankVector, vectorSize);
 
-		for (int j=0; j<vectorSize; ++j) {
-			sum += transitionMatrix[i][j] * previousPagerankVector[j];
-		}
-		(*pagerankVector)[i] = dampingFactor * sum;
+	for (int i=0; i<vectorSize; ++i) {
+		(*pagerankVector)[i] = dampingFactor * (*pagerankVector)[i];
 	}
 
 	double normDifference = vectorNorm(previousPagerankVector, vectorSize) -
 	vectorNorm(*pagerankVector, vectorSize);
 
 	for (int i=0; i<vectorSize; ++i) {
-		(*pagerankVector)[i] += normDifference * webUniformProbability +
-		linksFromConvergedPagesPagerankVector[i] + convergedPagerankVector[i];
+		(*pagerankVector)[i] += normDifference * webUniformProbability;
 	}
 }
 
@@ -222,32 +180,6 @@ double vectorNorm(double *vector, int vectorSize) {
 	return norm;
 }
 
-/*
- * transposeMatrix transposes the matrix passed (by reference) in the arguments.
-*/
-void transposeMatrix(double ***matrix, int rows, int columns) {
-	// Transposes the matrix
-	// Rows become columns and vice versa
-
-	double **tempArray = (double **) malloc(columns * sizeof(double *));
-	for (int i=0; i<columns; ++i) {
-		tempArray[i] = malloc(rows * sizeof(double));
-
-		for (int j=0; j<rows; ++j) {
-			tempArray[i][j] = (*matrix)[j][i];
-		}
-	}
-
-	// TODO free memory
-
-	//double **pointerToFreeMemoryLater = *matrix;
-	*matrix = tempArray;
-	/*for (int i=0; i<rows; ++i) {
-		free(pointerToFreeMemoryLater[i]);
-	}
-	free(pointerToFreeMemoryLater);*/
-}
-
 // ==================== PROGRAM INPUT AND OUTPUT UTILS ====================
 
 /*
@@ -323,7 +255,8 @@ void parseArguments(int argumentCount, char **argumentVector, Parameters *parame
  * readGraphFromFile loads the file supplied in the command line arguments to an
  * array (directedWebGraph) that represents the graph.
 */
-void readGraphFromFile(int ***directedWebGraph, Parameters *parameters) {
+void generateNormalizedTransitionMatrixFromFile(SparseMatrix *transitionMatrix,
+	Parameters *parameters){
 	FILE *graphFile;
 
 	// Opens the file for reading
@@ -333,38 +266,71 @@ void readGraphFromFile(int ***directedWebGraph, Parameters *parameters) {
 		exit(EXIT_FAILURE);
 	}
 
-	// Reads the dimensions of the (square) array from the file
-	int readChar, numberOfLines=0;
-	while((readChar = fgetc(graphFile))) {
-		// Breaks if end of file
-		if (readChar == EOF) break;
-		// Otherwise, if the character is a break line, adds one to the count of lines
-		if (readChar == '\n') {
-			++numberOfLines;
+	int pageIndex, count = 0;
+	while (fscanf(graphFile, "%d:", &pageIndex) != EOF) {
+		if (!(pageIndex%51050)) {
+			printf("\t%d\t%d%%\n", pageIndex, ++count);
 		}
-	}
 
-	if ((*parameters).verbose) {
-		printf("Line count of file is %d \n", numberOfLines + 1);
-	}
+		char *restOfLine = malloc(MAX_PAGE_LINKS_TEXT_SIZE);
+		if (!fgets(restOfLine, MAX_PAGE_LINKS_TEXT_SIZE, graphFile)) {
+			exit(EXIT_FAILURE);
+		}
 
-	// Each line of the file represents one page of the graph
-	(*parameters).numberOfPages = numberOfLines + 1;
-	rewind(graphFile);
+		char *token = strtok(restOfLine, " ");
 
-	// Allocates memory and loads values into directedWebGraph (matrix A)
-	// Allocates memory for the rows
-	(*directedWebGraph) = (int **) malloc((*parameters).numberOfPages * sizeof(int *));
+		while (token != NULL) {
+			if (strcmp(token, "\n") == 0) {
+				//token = strtok (NULL, " ");
+				break;
+			}
 
-	for (int i=0; i<(*parameters).numberOfPages; ++i) {
-		// Allocates memory for the columns of this row
-		(*directedWebGraph)[i] = (int *) malloc((*parameters).numberOfPages * sizeof(int));
-		// Reads values from the file
-		for (int j=0; j<(*parameters).numberOfPages; ++j) {
-			if (!fscanf(graphFile, "%d ", &(*directedWebGraph)[i][j])) {
+			int outLink = atoi(token);
+			if (outLink != -1) {
+				apendElement(transitionMatrix, 1, pageIndex, outLink);
+			}
+			token = strtok (NULL, " ");
+		}
+	}
+	printf("\t100%%\n");
+	printf("number of edges = %d\n", transitionMatrix->elements);
+
+	(*parameters).numberOfPages = pageIndex + 1;
+
+	int currentRow = transitionMatrix->firstElement->rowIndex;
+	SparseMatrixElement *startElement = transitionMatrix->firstElement;
+	while(true) {
+		int pageOutdegree = 1;
+		SparseMatrixElement *currentElement = startElement->nextElement;
+
+		// Calculates current page's outdegree
+		while (currentElement != NULL) {
+			if (currentElement->rowIndex == currentRow) {
+				++pageOutdegree;
+				currentElement = currentElement->nextElement;
+			} else {
 				break;
 			}
 		}
+
+		// Assigns the value 1/outdegree to current page's columns
+		currentElement = startElement;
+		for (int i=0; i<pageOutdegree; ++i) {
+			if (currentElement->rowIndex == currentRow) {
+				currentElement->value = 1. / pageOutdegree;
+				currentElement = currentElement->nextElement;
+			} else {
+				break;
+			}
+		}
+
+		// Reached the last element;
+		if (currentElement == NULL) {
+			break;
+		}
+
+		startElement = currentElement;
+		currentRow = startElement->rowIndex;
 	}
 
 	fclose(graphFile);
diff --git a/serial/serial_gs_pagerank_functions.h b/serial/serial_gs_pagerank_functions.h
index 9581c7b..853f8a0 100644
--- a/serial/serial_gs_pagerank_functions.h
+++ b/serial/serial_gs_pagerank_functions.h
@@ -7,6 +7,8 @@
 #include <string.h>
 #include <math.h>
 
+#include "sparse_matrix.h"
+
 /*
  * Constant strings that store the command line options available.
 */
@@ -23,6 +25,8 @@ extern const int NUMERICAL_BASE;
 // Default filename used for the output.
 extern char *DEFAULT_OUTPUT_FILENAME;
 
+extern const int MAX_PAGE_LINKS_TEXT_SIZE;
+
 // Declares a data structure to conveniently hold the algorithm's parameters.
 typedef struct parameters {
 	int numberOfPages, maxIterations;
@@ -31,6 +35,9 @@ typedef struct parameters {
 	char *outputFilename, *graphFilename;
 } Parameters;
 
+//extern typedef SparseMatrixElement;
+//extern typedef SparseMatrix;
+
 // Function validUsage outputs the correct way to use the program with command
 // line arguments.
 void validUsage(char *programName);
@@ -45,26 +52,17 @@ void parseArguments(int argumentCount, char **argumentVector, Parameters *parame
 // Function readGraphFromFile loads adjacency matrix, that represents the web
 // graph, stored in the file provided in the command line arguments to the array
 // directedWebGraph.
-void readGraphFromFile(int ***directedWebGraph, Parameters *parameters);
+void generateNormalizedTransitionMatrixFromFile(SparseMatrix *transitionMatrix, Parameters *parameters);
 
 // Function savePagerankToFile appends or overwrites the pagerank vector
 // "pagerankVector" to the file with the filename supplied in the arguments 
 void savePagerankToFile(char *filename, bool append, double *pagerankVector,
 	int vectorSize);
 
-// Function generateNormalizedTransitionMatrix generates the normalized
-// transition matrix from the web graph data.
-void generateNormalizedTransitionMatrix(double ***transitionMatrix,
-	int **directedWebGraph, Parameters parameters);
-
-// Function transposeMatrix transposes a matrix.
-void transposeMatrix(double ***matrix, int rows, int columns);
-
 // Function initialize allocates required memory for arrays, reads the dataset
 // from the file and creates the transition probability distribution matrix.
 void initialize(
-	int ***directedWebGraph, /*This is matrix G (web graph)*/
-	double ***transitionMatrix, /*This is matrix A (transition probability distribution matrix)*/
+	SparseMatrix *transitionMatrix, /*This is matrix A (transition probability distribution matrix)*/
 	double **pagerankVector, /*This is the resulting pagerank vector*/
 	Parameters *parameters
 	);
@@ -74,13 +72,13 @@ double vectorNorm(double *vector, int vectorSize);
 
 // Function matrixVectorMultiplication calculates the product of the
 // multiplication between a matrix and the a vector.
-void matrixVectorMultiplication(double **transitionMatrix, double *previousPagerankVector,
-			double *linksFromConvergedPagesPagerankVector, double *convergedPagerankVector,
-			double **pagerankVector, int vectorSize, double dampingFactor);
+void matrixVectorMultiplication(SparseMatrix *transitionMatrix,
+	double *previousPagerankVector, double **pagerankVector, int vectorSize,
+	double dampingFactor);
 
 // Function pagerank iteratively calculates the pagerank of each page until
 // either the convergence criterion is met or the maximum number of iterations
 // is reached.
-int pagerank(double ***transitionMatrix, double **pagerankVector, Parameters parameters);
+int pagerank(SparseMatrix *transitionMatrix, double **pagerankVector, Parameters parameters);
 
 #endif	// SERIAL_GS_PAGERANK_FUNCTIONS_H
\ No newline at end of file
diff --git a/serial/sparse_matrix.c b/serial/sparse_matrix.c
new file mode 100644
index 0000000..ba77587
--- /dev/null
+++ b/serial/sparse_matrix.c
@@ -0,0 +1,126 @@
+#include "sparse_matrix.h"
+
+SparseMatrix createSparseMatrix() {
+	SparseMatrix sparseMatrix;
+	sparseMatrix.elements = 0;
+	sparseMatrix.firstElement = NULL;
+	return sparseMatrix;
+}
+
+void apendElement(SparseMatrix *sparseMatrix, double value, int row, int column) {
+	// Creates the new element
+	SparseMatrixElement *newElement = (SparseMatrixElement *) malloc(sizeof(SparseMatrixElement));
+	newElement->value = value;
+	newElement->rowIndex = row;
+	newElement->columnIndex = column;
+	newElement->nextElement = NULL;
+
+	if (sparseMatrix->firstElement == NULL) {
+		// Sparse matrix is empty, this is the first element
+		sparseMatrix->firstElement = newElement;
+	} else {
+		//Gets last element of the matrix
+		SparseMatrixElement *lastElement = sparseMatrix->firstElement;
+		while (lastElement->nextElement != NULL) {
+			lastElement = lastElement->nextElement;
+		}
+
+		lastElement->nextElement = newElement;
+	}
+
+	sparseMatrix->elements = sparseMatrix->elements + 1;
+}
+
+bool deleteElement(SparseMatrix *sparseMatrix, int row, int column) {
+	if (sparseMatrix->elements == 0) {
+		// Matrix is empty, nothing can be deleted
+		return false;
+	} else if (sparseMatrix->elements == 1) {
+		// Matrix has one element. Deletes it.
+		free(sparseMatrix->firstElement);
+		sparseMatrix->firstElement = NULL;
+		sparseMatrix->elements = sparseMatrix->elements - 1;
+		return true;
+	}
+
+	SparseMatrixElement *currentElement = sparseMatrix->firstElement;
+
+	if (currentElement->rowIndex == row && currentElement->columnIndex == column) {
+		sparseMatrix->firstElement = currentElement->nextElement;
+		free(currentElement);
+		sparseMatrix->elements = sparseMatrix->elements - 1;
+		return true;
+	}
+
+	// Matrix has multiple elements. Finds the first element that has the coordinates
+	// (row,column) and deletes it.
+	for (int i=0; i<sparseMatrix->elements - 1; ++i) {
+		SparseMatrixElement *nextElement = currentElement->nextElement;
+		if (nextElement->rowIndex == row && nextElement->columnIndex == column) {
+			currentElement->nextElement = nextElement->nextElement;
+			free(nextElement);
+			sparseMatrix->elements = sparseMatrix->elements - 1;
+			return true;
+		} else {
+			currentElement = currentElement->nextElement;
+		}
+	}
+}
+
+SparseMatrixElement *getElement(SparseMatrix sparseMatrix, int row, int column) {
+	SparseMatrixElement *currentElement = sparseMatrix.firstElement;
+	do {
+		if (currentElement->rowIndex == row && currentElement->columnIndex == column) {
+			return currentElement;
+		}
+		currentElement = currentElement->nextElement;
+	} while (currentElement != NULL);
+
+	return NULL;
+}
+
+void transposeSparseMatrix(SparseMatrix *sparseMatrix) {
+	SparseMatrixElement *currentElement = sparseMatrix->firstElement;
+	for (int i=0; i<sparseMatrix->elements; ++i) {
+		int temp = currentElement->rowIndex;
+		currentElement->rowIndex = currentElement->columnIndex;
+		currentElement->columnIndex = temp;
+
+		currentElement = currentElement->nextElement;
+	}
+}
+
+void sparseMatrixVectorMultiplication(SparseMatrix sparseMatrix,
+	double *vector, double **product, int vectorSize) {
+	// Initializes the elements of the product vector to zero
+	for (int i=0; i<vectorSize; ++i) {
+		(*product)[i] = 0;
+	}
+
+	SparseMatrixElement *element = sparseMatrix.firstElement;
+	for (int i=0; i<sparseMatrix.elements; ++i) {
+		int row = element->rowIndex, column = element->columnIndex;
+
+		if (row >= vectorSize) {
+			printf("Error at sparseMatrixVectorMultiplication. Matrix has more rows than vector!\n");
+			printf("row = %d\n", row);
+			exit(EXIT_FAILURE);
+		}
+
+		(*product)[row] = (*product)[row] + element->value * vector[column];
+		element = element->nextElement;
+	}
+}
+
+void printSparseMatrix(SparseMatrix sparseMatrix) {
+	if (sparseMatrix.elements == 0) {
+		return;
+	}
+
+	SparseMatrixElement *currentElement = sparseMatrix.firstElement;
+	for (int i=0; i<sparseMatrix.elements; ++i) {
+		printf("[%d,%d] = %f\n", currentElement->rowIndex,
+			currentElement->columnIndex, currentElement->value);
+		currentElement = currentElement->nextElement;
+	}
+}
\ No newline at end of file
diff --git a/serial/sparse_matrix.h b/serial/sparse_matrix.h
new file mode 100644
index 0000000..cfa7f8e
--- /dev/null
+++ b/serial/sparse_matrix.h
@@ -0,0 +1,29 @@
+#ifndef SPARSE_MATRIX_H	/* Include guard */
+#define SPARSE_MATRIX_H
+
+#include <stdbool.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+typedef struct sparseMatrixElement {
+	double value;
+	int rowIndex, columnIndex;
+	struct sparseMatrixElement *nextElement;
+} SparseMatrixElement;
+
+typedef struct sparseMatrix {
+	int elements;
+	SparseMatrixElement *firstElement;
+} SparseMatrix;
+
+SparseMatrix createSparseMatrix();
+void apendElement(SparseMatrix *sparseMatrix, double value, int row, int column);
+bool deleteElement(SparseMatrix *sparseMatrix, int row, int column);
+SparseMatrixElement *getElement(SparseMatrix sparseMatrix, int row, int column);
+void transposeSparseMatrix(SparseMatrix *sparseMatrix);
+void sparseMatrixVectorMultiplication(SparseMatrix sparseMatrix, double *vector,
+	double **product, int vectorSize);
+void printSparseMatrix(SparseMatrix sparseMatrix);
+
+#endif	// SPARSE_MATRIX_H
\ No newline at end of file