From a142a02a04368fa0b6255391101efd7079089100 Mon Sep 17 00:00:00 2001
From: Apostolof <apotwohd@gmail.com>
Date: Sat, 29 Sep 2018 01:41:49 +0300
Subject: [PATCH] Change transition matrix to CSR, Remove LIL

---
 serial/Makefile                       |  4 +-
 serial/coo_sparse_matrix.c            | 96 +++++++++++++++------------
 serial/coo_sparse_matrix.h            | 18 ++---
 serial/csr_sparse_matrix.c            | 93 ++++++++++++++++++++++++++
 serial/csr_sparse_matrix.h            | 24 +++++++
 serial/lil_sparse_matrix.c            | 76 ---------------------
 serial/lil_sparse_matrix.h            | 29 --------
 serial/serial_gs_pagerank.c           |  4 +-
 serial/serial_gs_pagerank_functions.c | 79 +++++++++++-----------
 serial/serial_gs_pagerank_functions.h |  9 ++-
 10 files changed, 229 insertions(+), 203 deletions(-)
 create mode 100644 serial/csr_sparse_matrix.c
 create mode 100644 serial/csr_sparse_matrix.h
 delete mode 100644 serial/lil_sparse_matrix.c
 delete mode 100644 serial/lil_sparse_matrix.h

diff --git a/serial/Makefile b/serial/Makefile
index 9c4e0e6..b321b1d 100644
--- a/serial/Makefile
+++ b/serial/Makefile
@@ -7,8 +7,8 @@ CC = gcc
 RM = rm -f
 CFLAGS_DEBUG=-O0 -ggdb3 -Wall -I.
 CFLAGS=-O3 -Wall -I.
-OBJ=serial_gs_pagerank.o serial_gs_pagerank_functions.o coo_sparse_matrix.o lil_sparse_matrix.o
-DEPS=serial_gs_pagerank_functions.h coo_sparse_matrix.h lil_sparse_matrix.h
+OBJ=serial_gs_pagerank.o serial_gs_pagerank_functions.o coo_sparse_matrix.o csr_sparse_matrix.o
+DEPS=serial_gs_pagerank_functions.h coo_sparse_matrix.h csr_sparse_matrix.h
 
 # ==========================================
 # TARGETS
diff --git a/serial/coo_sparse_matrix.c b/serial/coo_sparse_matrix.c
index 42fc7f1..93d0ac9 100644
--- a/serial/coo_sparse_matrix.c
+++ b/serial/coo_sparse_matrix.c
@@ -3,16 +3,25 @@
 CooSparseMatrix initCooSparseMatrix() {
 	CooSparseMatrix sparseMatrix;
 	sparseMatrix.size = 0;
+	sparseMatrix.numberOfNonZeroElements = 0;
 	sparseMatrix.elements = NULL;
 	return sparseMatrix;
 }
 
-void allocMemoryForElements (CooSparseMatrix *sparseMatrix, int elements) {
+void allocMemoryForCoo(CooSparseMatrix *sparseMatrix, int numberOfElements) {
 	sparseMatrix->elements = (CooSparseMatrixElement **) malloc(
-		elements * sizeof(CooSparseMatrixElement *));
+		numberOfElements * sizeof(CooSparseMatrixElement *));
+	sparseMatrix->size = numberOfElements;
 }
 
 void addElement(CooSparseMatrix *sparseMatrix, double value, int row, int column) {
+	if (sparseMatrix->numberOfNonZeroElements == sparseMatrix->size) {
+		printf("%d == %d |||| %d, %d\n", sparseMatrix->numberOfNonZeroElements,
+			sparseMatrix->size, row, column);
+		printf("Number of non zero elements exceeded size of matrix!\n");
+		exit(EXIT_FAILURE);
+	}
+
 	// Creates the new element
 	CooSparseMatrixElement *newElement = (CooSparseMatrixElement *) malloc(
 		sizeof(CooSparseMatrixElement));
@@ -20,58 +29,57 @@ void addElement(CooSparseMatrix *sparseMatrix, double value, int row, int column
 	newElement->rowIndex = row;
 	newElement->columnIndex = column;
 
-	sparseMatrix->elements[sparseMatrix->size] = newElement;
-	sparseMatrix->size = sparseMatrix->size + 1;
+	sparseMatrix->elements[sparseMatrix->numberOfNonZeroElements] = newElement;
+	sparseMatrix->numberOfNonZeroElements = sparseMatrix->numberOfNonZeroElements + 1;
 }
 
-void zeroOutRow(CooSparseMatrix *sparseMatrix, int row) {
-	for (int i=0; i<sparseMatrix->size; ++i) {
-		CooSparseMatrixElement *element = sparseMatrix->elements[i];
-		if (element->rowIndex == row) {
-			element->value = 0;
-		}
-	}
-}
-void zeroOutColumn(CooSparseMatrix *sparseMatrix, int column) {
-	for (int i=0; i<sparseMatrix->size; ++i) {
+void transposeSparseMatrix(CooSparseMatrix *sparseMatrix) {
+	for (int i=0; i<sparseMatrix->numberOfNonZeroElements; ++i) {
 		CooSparseMatrixElement *element = sparseMatrix->elements[i];
-		if (element->columnIndex == column) {
-			element->value = 0;
-		}
+		int tempRow = element->rowIndex;
+		element->rowIndex = element->columnIndex;
+		element->columnIndex = tempRow;
 	}
 }
 
-int *getRowIndexes(CooSparseMatrix sparseMatrix, int row, int *rowSize) {
-	*rowSize = 0;
-	for (int i=0; i<sparseMatrix.size; ++i) {
-		if (sparseMatrix.elements[i]->rowIndex == row) {
-			++(*rowSize);
-		}
+void transformToCSR(CooSparseMatrix initialSparseMatrix,
+	CsrSparseMatrix *transformedSparseMatrix) {
+	// Taken from here: https://github.com/scipy/scipy/blob/3b36a57/scipy/sparse/sparsetools/coo.h#L34
+	if (initialSparseMatrix.numberOfNonZeroElements > transformedSparseMatrix->size) {
+		printf("Transformed CSR matrix does not have enough space!\n");
+		exit(EXIT_FAILURE);
 	}
 
-	if (!(*rowSize)) {
-		return NULL;
+	for (int i=0; i<initialSparseMatrix.numberOfNonZeroElements; ++i){
+		int rowIndex = initialSparseMatrix.elements[i]->rowIndex;
+		transformedSparseMatrix->rowCumulativeIndexes[rowIndex] = 
+		transformedSparseMatrix->rowCumulativeIndexes[rowIndex] + 1;
 	}
 
-	int *indexes = (int *) malloc((*rowSize) * sizeof(int));
-	int rowElementIndex = 0;
-	for (int i=0; i<sparseMatrix.size; ++i) {
-		if (sparseMatrix.elements[i]->rowIndex == row) {
-			indexes[rowElementIndex] = i;
-			++rowElementIndex;
-		}
+	// Cumulative sums the non zero elements per row
+	for (int i=0, sum=0; i<transformedSparseMatrix->size+1; ++i){
+		int temp = transformedSparseMatrix->rowCumulativeIndexes[i];
+		transformedSparseMatrix->rowCumulativeIndexes[i] = sum;
+		sum += temp;
 	}
 
-	return indexes;
-}
+	for (int i=0; i<initialSparseMatrix.numberOfNonZeroElements; ++i){
+		int row  = initialSparseMatrix.elements[i]->rowIndex;
+		int destinationIndex = transformedSparseMatrix->rowCumulativeIndexes[row];
 
-void transposeSparseMatrix(CooSparseMatrix *sparseMatrix) {
-	for (int i=0; i<sparseMatrix->size; ++i) {
-		CooSparseMatrixElement *element = sparseMatrix->elements[i];
-		int tempRow = element->rowIndex;
-		element->rowIndex = element->columnIndex;
-		element->columnIndex = tempRow;
+		transformedSparseMatrix->columnIndexes[destinationIndex] = initialSparseMatrix.elements[i]->columnIndex;
+		transformedSparseMatrix->values[destinationIndex] = initialSparseMatrix.elements[i]->value;
+
+		transformedSparseMatrix->rowCumulativeIndexes[row]++;
 	}
+
+	for (int i=0, last=0; i<=transformedSparseMatrix->size; i++){
+		int temp = transformedSparseMatrix->rowCumulativeIndexes[i];
+		transformedSparseMatrix->rowCumulativeIndexes[i] = last;
+		last = temp;
+	}
+
+	transformedSparseMatrix->numberOfNonZeroElements = initialSparseMatrix.numberOfNonZeroElements;
 }
 
 void cooSparseMatrixVectorMultiplication(CooSparseMatrix sparseMatrix,
@@ -82,7 +90,7 @@ void cooSparseMatrixVectorMultiplication(CooSparseMatrix sparseMatrix,
 	}
 
 	CooSparseMatrixElement *element;
-	for (int i=0; i<sparseMatrix.size; ++i) {
+	for (int i=0; i<sparseMatrix.numberOfNonZeroElements; ++i) {
 		element = sparseMatrix.elements[i];
 		int row = element->rowIndex, column = element->columnIndex;
 
@@ -97,19 +105,19 @@ void cooSparseMatrixVectorMultiplication(CooSparseMatrix sparseMatrix,
 }
 
 void destroyCooSparseMatrix(CooSparseMatrix *sparseMatrix) {
-	for (int i=0; i<sparseMatrix->size; ++i) {
+	for (int i=0; i<sparseMatrix->numberOfNonZeroElements; ++i) {
 		free(sparseMatrix->elements[i]);
 	}
 	free(sparseMatrix->elements);
 }
 
 void printCooSparseMatrix(CooSparseMatrix sparseMatrix) {
-	if (sparseMatrix.size == 0) {
+	if (sparseMatrix.numberOfNonZeroElements == 0) {
 		return;
 	}
 
 	CooSparseMatrixElement *element;
-	for (int i=0; i<sparseMatrix.size; ++i) {
+	for (int i=0; i<sparseMatrix.numberOfNonZeroElements; ++i) {
 		element = sparseMatrix.elements[i];
 		printf("[%d,%d] = %f\n", element->rowIndex, element->columnIndex,
 			element->value);
diff --git a/serial/coo_sparse_matrix.h b/serial/coo_sparse_matrix.h
index 66f538b..dd4c31d 100644
--- a/serial/coo_sparse_matrix.h
+++ b/serial/coo_sparse_matrix.h
@@ -6,25 +6,27 @@
 #include <stdio.h>
 #include <stdlib.h>
 
+#include "csr_sparse_matrix.h"
+
 typedef struct cooSparseMatrixElement {
 	double value;
 	int rowIndex, columnIndex;
 } CooSparseMatrixElement;
 
 typedef struct cooSparseMatrix {
-	int size;
+	int size, numberOfNonZeroElements;
 	CooSparseMatrixElement **elements;
 } CooSparseMatrix;
 
 CooSparseMatrix initCooSparseMatrix();
-void allocMemoryForElements (CooSparseMatrix *sparseMatrix, int elements);
-void addElement(CooSparseMatrix *sparseMatrix, double value, int row, int column);
-void zeroOutRow(CooSparseMatrix *sparseMatrix, int row);
-void zeroOutColumn(CooSparseMatrix *sparseMatrix, int column);
-int *getRowIndexes(CooSparseMatrix sparseMatrix, int row, int *rowSize);
+void allocMemoryForCoo(CooSparseMatrix *sparseMatrix, int numberOfElements);
+void addElement(CooSparseMatrix *sparseMatrix, double value, int row,
+	int column);
 void transposeSparseMatrix(CooSparseMatrix *sparseMatrix);
-void cooSparseMatrixVectorMultiplication(CooSparseMatrix sparseMatrix, double *vector,
-	double **product, int vectorSize);
+void transformToCSR(CooSparseMatrix initialSparseMatrix,
+	CsrSparseMatrix *transformedSparseMatrix);
+void cooSparseMatrixVectorMultiplication(CooSparseMatrix sparseMatrix,
+	double *vector, double **product, int vectorSize);
 void destroyCooSparseMatrix(CooSparseMatrix *sparseMatrix);
 void printCooSparseMatrix(CooSparseMatrix sparseMatrix);
 
diff --git a/serial/csr_sparse_matrix.c b/serial/csr_sparse_matrix.c
new file mode 100644
index 0000000..bdf8413
--- /dev/null
+++ b/serial/csr_sparse_matrix.c
@@ -0,0 +1,93 @@
+#include "csr_sparse_matrix.h"
+
+CsrSparseMatrix initCsrSparseMatrix() {
+	CsrSparseMatrix sparseMatrix;
+	sparseMatrix.size = 0;
+	sparseMatrix.numberOfNonZeroElements = 0;
+
+	sparseMatrix.values = NULL;
+	sparseMatrix.columnIndexes = NULL;
+	sparseMatrix.rowCumulativeIndexes = NULL;
+	return sparseMatrix;
+}
+
+void allocMemoryForCsr(CsrSparseMatrix *sparseMatrix, int numberOfElements) {
+	sparseMatrix->values = (double *) malloc(numberOfElements * sizeof(double));
+	sparseMatrix->columnIndexes = (int *) malloc(
+		numberOfElements * sizeof(int));
+	sparseMatrix->rowCumulativeIndexes = (int *) malloc(
+		(numberOfElements + 1) * sizeof(int));
+
+	for (int i=0; i<numberOfElements+1; ++i) {
+		sparseMatrix->rowCumulativeIndexes[i] = 0;
+	}
+	sparseMatrix->size = numberOfElements;
+}
+
+// Row indexes start from 0!
+void zeroOutRow(CsrSparseMatrix *sparseMatrix, int row) {
+	int startIndex = sparseMatrix->rowCumulativeIndexes[row],
+	endIndex = sparseMatrix->rowCumulativeIndexes[row+1];
+	for (int i=startIndex; i<endIndex; ++i) {
+		sparseMatrix->values[i] = 0;
+	}
+}
+
+void zeroOutColumn(CsrSparseMatrix *sparseMatrix, int column) {
+	for (int i=0; i<sparseMatrix->numberOfNonZeroElements; ++i){
+		if(sparseMatrix->columnIndexes[i] == column){
+			// Zeros out this element
+			sparseMatrix->values[i] = 0;
+		}
+	}
+}
+
+void csrSparseMatrixVectorMultiplication(CsrSparseMatrix 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;
+	}
+
+	for (int i=0; i<sparseMatrix.size; ++i) {
+		// Gets start and end indexes of this row's elements
+		int startIndex = sparseMatrix.rowCumulativeIndexes[i],
+		endIndex = sparseMatrix.rowCumulativeIndexes[i+1];
+
+		if (startIndex == endIndex) {
+			// This row has no elements
+			continue;
+		}
+
+		double sum = 0;
+		for(int j=startIndex; j<endIndex; ++j){
+			int elementColumn = sparseMatrix.columnIndexes[j];
+			sum += sparseMatrix.values[j] * vector[elementColumn];
+		}
+
+		(*product)[i] = sum;
+	}
+}
+
+void destroyCsrSparseMatrix(CsrSparseMatrix *sparseMatrix) {
+	free(sparseMatrix->values);
+	free(sparseMatrix->rowCumulativeIndexes);
+	free(sparseMatrix->columnIndexes);
+}
+
+void printCsrSparseMatrix(CsrSparseMatrix sparseMatrix) {
+	if (sparseMatrix.size == 0) {
+		return;
+	}
+
+	for (int i=0; i<sparseMatrix.size; ++i){
+		int startIndex = sparseMatrix.rowCumulativeIndexes[i],
+		endIndex = sparseMatrix.rowCumulativeIndexes[i+1];
+		for(int j=startIndex; j<endIndex; ++j){
+			printf("Row [%d] has [%d] nz elements: \n at column[%d] is value = %f \n",
+				i, endIndex-startIndex,
+				sparseMatrix.columnIndexes[j],
+				sparseMatrix.values[j]);
+		}
+	}
+}
diff --git a/serial/csr_sparse_matrix.h b/serial/csr_sparse_matrix.h
new file mode 100644
index 0000000..a964514
--- /dev/null
+++ b/serial/csr_sparse_matrix.h
@@ -0,0 +1,24 @@
+#ifndef CSR_SPARSE_MATRIX_H	/* Include guard */
+#define CSR_SPARSE_MATRIX_H
+
+#include <stdbool.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+typedef struct csrSparseMatrix {
+	int size, numberOfNonZeroElements;
+	int *rowCumulativeIndexes, *columnIndexes;
+	double *values;
+} CsrSparseMatrix;
+
+CsrSparseMatrix initCsrSparseMatrix();
+void allocMemoryForCsr(CsrSparseMatrix *sparseMatrix, int numberOfElements);
+void zeroOutRow(CsrSparseMatrix *sparseMatrix, int row);
+void zeroOutColumn(CsrSparseMatrix *sparseMatrix, int column);
+void csrSparseMatrixVectorMultiplication(CsrSparseMatrix sparseMatrix,
+	double *vector, double **product, int vectorSize);
+void destroyCsrSparseMatrix(CsrSparseMatrix *sparseMatrix);
+void printCsrSparseMatrix(CsrSparseMatrix sparseMatrix);
+
+#endif	// CSR_SPARSE_MATRIX_H
\ No newline at end of file
diff --git a/serial/lil_sparse_matrix.c b/serial/lil_sparse_matrix.c
deleted file mode 100644
index 61777ea..0000000
--- a/serial/lil_sparse_matrix.c
+++ /dev/null
@@ -1,76 +0,0 @@
-#include "lil_sparse_matrix.h"
-
-LilSparseMatrix createLilSparseMatrix() {
-	LilSparseMatrix sparseMatrix;
-	sparseMatrix.elements = 0;
-	sparseMatrix.firstElement = NULL;
-	sparseMatrix.lastElement = NULL;
-	return sparseMatrix;
-}
-
-void apendElement(LilSparseMatrix *sparseMatrix, double value, int row, int column) {
-	// Creates the new element
-	LilSparseMatrixElement *newElement = (LilSparseMatrixElement *) malloc(sizeof(LilSparseMatrixElement));
-	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;
-		sparseMatrix->lastElement = newElement;
-	} else {
-		//Gets last element of the matrix
-		LilSparseMatrixElement *lastElement = sparseMatrix->lastElement;
-
-		lastElement->nextElement = newElement;
-		sparseMatrix->lastElement = newElement;
-	}
-
-	sparseMatrix->elements = sparseMatrix->elements + 1;
-}
-
-void lilSparseMatrixVectorMultiplication(LilSparseMatrix 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;
-	}
-
-	LilSparseMatrixElement *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 destroyLilSparseMatrix(LilSparseMatrix *sparseMatrix) {
-	LilSparseMatrixElement *currentElement = sparseMatrix->firstElement;
-	while (currentElement != NULL) {
-		LilSparseMatrixElement *toDelete = currentElement;
-		currentElement = currentElement->nextElement;
-		free(toDelete);
-	}
-}
-
-void printLilSparseMatrix(LilSparseMatrix sparseMatrix) {
-	if (sparseMatrix.elements == 0) {
-		return;
-	}
-
-	LilSparseMatrixElement *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/lil_sparse_matrix.h b/serial/lil_sparse_matrix.h
deleted file mode 100644
index 599cdae..0000000
--- a/serial/lil_sparse_matrix.h
+++ /dev/null
@@ -1,29 +0,0 @@
-#ifndef LIL_SPARSE_MATRIX_H	/* Include guard */
-#define LIL_SPARSE_MATRIX_H
-
-#include <stdbool.h>
-#include <stdlib.h>
-#include <stdio.h>
-#include <stdlib.h>
-
-typedef struct lilSparseMatrixElement {
-	double value;
-	int rowIndex, columnIndex;
-	struct lilSparseMatrixElement *nextElement;
-} LilSparseMatrixElement;
-
-typedef struct lilSparseMatrix {
-	int elements;
-	LilSparseMatrixElement *firstElement;
-	LilSparseMatrixElement *lastElement;
-} LilSparseMatrix;
-
-LilSparseMatrix createLilSparseMatrix();
-void apendElement(LilSparseMatrix *sparseMatrix, double value, int row,
-	int column);
-void lilSparseMatrixVectorMultiplication(LilSparseMatrix sparseMatrix,
-	double *vector, double **product, int vectorSize);
-void destroyLilSparseMatrix(LilSparseMatrix *sparseMatrix);
-void printLilSparseMatrix(LilSparseMatrix sparseMatrix);
-
-#endif	// LIL_SPARSE_MATRIX_H
\ No newline at end of file
diff --git a/serial/serial_gs_pagerank.c b/serial/serial_gs_pagerank.c
index 9a4cf6f..dd9a6e7 100644
--- a/serial/serial_gs_pagerank.c
+++ b/serial/serial_gs_pagerank.c
@@ -7,7 +7,7 @@ struct timeval startwtime, endwtime;
 double seq_time;
 
 int main(int argc, char **argv) {
-	CooSparseMatrix transitionMatrix = initCooSparseMatrix();
+	CsrSparseMatrix transitionMatrix = initCsrSparseMatrix();
 	double *pagerankVector;
 	bool convergenceStatus;
 	Parameters parameters;
@@ -40,5 +40,5 @@ int main(int argc, char **argv) {
 		seq_time);
 
 	free(pagerankVector);
-	destroyCooSparseMatrix(&transitionMatrix);
+	destroyCsrSparseMatrix(&transitionMatrix);
 }
diff --git a/serial/serial_gs_pagerank_functions.c b/serial/serial_gs_pagerank_functions.c
index b8b9e9e..98fd38c 100644
--- a/serial/serial_gs_pagerank_functions.c
+++ b/serial/serial_gs_pagerank_functions.c
@@ -16,17 +16,17 @@ char *DEFAULT_OUTPUT_FILENAME = "pagerank_output";
 const int FILE_READ_BUFFER_SIZE = 4096;
 
 const int CONVERGENCE_CHECK_ITERATION_PERIOD = 3;
-const int SPARSITY_INCREASE_ITERATION_PERIOD = 9;
+const int SPARSITY_INCREASE_ITERATION_PERIOD = 3;
 
 /* ===== FUNCTIONS ===== */
 
-int pagerank(CooSparseMatrix *transitionMatrix, double **pagerankVector,
+int pagerank(CsrSparseMatrix *transitionMatrix, double **pagerankVector,
 	bool *convergenceStatus, Parameters parameters) {
 	// Variables declaration
 	int iterations = 0, numberOfPages = parameters.numberOfPages;
 	double delta, *pagerankDifference, *previousPagerankVector,
 	*convergedPagerankVector, *linksFromConvergedPagesPagerankVector;
-	LilSparseMatrix linksFromConvergedPages = createLilSparseMatrix();
+	CooSparseMatrix linksFromConvergedPages = initCooSparseMatrix();
 	bool *convergenceMatrix;
 
 	// Space allocation
@@ -47,6 +47,7 @@ int pagerank(CooSparseMatrix *transitionMatrix, double **pagerankVector,
 		*convergenceStatus = false;
 
 		// Initialization
+		allocMemoryForCoo(&linksFromConvergedPages, transitionMatrix->numberOfNonZeroElements);
 		for (int i=0; i<numberOfPages; ++i) {
 			convergedPagerankVector[i] = 0;
 			convergenceMatrix[i] = false;
@@ -107,17 +108,21 @@ int pagerank(CooSparseMatrix *transitionMatrix, double **pagerankVector,
 			}
 
 			for (int i=0; i<numberOfPages; ++i) {
+				// Filters newly converged pages
 				if (newlyConvergedPages[i] == true) {
-					int rowSize;
-					int *rowIndexes = getRowIndexes(*transitionMatrix, i, &rowSize);
-					for (int j=0; j<rowSize; ++j){
-						CooSparseMatrixElement *element = transitionMatrix->elements[rowIndexes[j]];
-						// Checks for links from converged pages to non converged
-						int pageLinksTo = element->columnIndex;
-						if (convergenceMatrix[pageLinksTo] == false){
-							// Link exists, adds element to the vector
-							apendElement(&linksFromConvergedPages,
-								element->value, i, pageLinksTo);
+					// Checks if this converged page has an out-link to a non converged one
+					int rowStartIndex = transitionMatrix->rowCumulativeIndexes[i],
+					rowEndIndex = transitionMatrix->rowCumulativeIndexes[i+1];
+					if (rowEndIndex > rowStartIndex) {
+						// This row (page) has non zero elements (out-links)
+						for (int j=rowStartIndex; j<rowEndIndex; ++j) {
+							// Checks for links from converged pages to non converged
+							int pageLinksTo = transitionMatrix->columnIndexes[j];
+							if (convergenceMatrix[pageLinksTo] == false){
+								// Link exists, adds element to the vector
+								addElement(&linksFromConvergedPages,
+									transitionMatrix->values[j], i, pageLinksTo);
+							}
 						}
 					}
 
@@ -127,7 +132,7 @@ int pagerank(CooSparseMatrix *transitionMatrix, double **pagerankVector,
 					zeroOutColumn(transitionMatrix, i);
 
 					// Builds the new linksFromConvergedPagesPagerankVector
-					lilSparseMatrixVectorMultiplication(linksFromConvergedPages,
+					cooSparseMatrixVectorMultiplication(linksFromConvergedPages,
 						*pagerankVector, &linksFromConvergedPagesPagerankVector,
 						numberOfPages);
 				}
@@ -157,7 +162,7 @@ int pagerank(CooSparseMatrix *transitionMatrix, double **pagerankVector,
 	free(convergedPagerankVector);
 	free(linksFromConvergedPagesPagerankVector);
 	free(convergenceMatrix);
-	destroyLilSparseMatrix(&linksFromConvergedPages);
+	destroyCooSparseMatrix(&linksFromConvergedPages);
 
 	return iterations;
 }
@@ -167,7 +172,7 @@ int pagerank(CooSparseMatrix *transitionMatrix, double **pagerankVector,
  * from the file and creates the initial transition probability distribution
  * matrix.
 */
-void initialize(CooSparseMatrix *transitionMatrix,
+void initialize(CsrSparseMatrix *transitionMatrix,
 	double **pagerankVector, Parameters *parameters) {
 
 	// Reads web graph from file
@@ -197,9 +202,6 @@ void initialize(CooSparseMatrix *transitionMatrix,
 	for (int i=0; i<(*parameters).numberOfPages; ++i) {
 		(*pagerankVector)[i] = webUniformProbability;
 	}
-
-	// Transposes the transition matrix (P^T).
-	transposeSparseMatrix(transitionMatrix);
 }
 
 // ==================== MATH UTILS ====================
@@ -208,14 +210,14 @@ void initialize(CooSparseMatrix *transitionMatrix,
  * calculateNextPagerank calculates the product of the multiplication
  * between a matrix and the a vector in a cheap way.
 */
-void calculateNextPagerank(CooSparseMatrix *transitionMatrix,
+void calculateNextPagerank(CsrSparseMatrix *transitionMatrix,
 	double *previousPagerankVector, double **pagerankVector,
 	double *linksFromConvergedPagesPagerankVector,
 	double *convergedPagerankVector, int vectorSize, double dampingFactor) {
 	// Calculates the web uniform probability once.
 	double webUniformProbability = 1. / vectorSize;
 
-	cooSparseMatrixVectorMultiplication(*transitionMatrix, previousPagerankVector,
+	csrSparseMatrixVectorMultiplication(*transitionMatrix, previousPagerankVector,
 		pagerankVector, vectorSize);
 
 	for (int i=0; i<vectorSize; ++i) {
@@ -319,7 +321,7 @@ 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 generateNormalizedTransitionMatrixFromFile(CooSparseMatrix *transitionMatrix,
+void generateNormalizedTransitionMatrixFromFile(CsrSparseMatrix *transitionMatrix,
 	Parameters *parameters){
 	FILE *graphFile;
 
@@ -385,16 +387,12 @@ void generateNormalizedTransitionMatrixFromFile(CooSparseMatrix *transitionMatri
 		exit(EXIT_FAILURE);
 	}
 
-	int tenPercentIncrements = (int) numberOfEdges/10;
+	
 	int maxPageIndex = 0;
-	allocMemoryForElements(transitionMatrix, numberOfEdges);
+	CooSparseMatrix tempMatrix = initCooSparseMatrix();
+	allocMemoryForCoo(&tempMatrix, numberOfEdges);
 
 	for (int i=0; i<numberOfEdges; i++) {
-		if (((*parameters).verbose) && (tenPercentIncrements != 0) && ((i % tenPercentIncrements) == 0)) {
-			int percentage = (i/tenPercentIncrements)*10;
-			printf("%d%% • ", percentage);
-		}
-
 		int fileFrom = 0, fileTo = 0;
 		if (!fscanf(graphFile, "%d %d", &fileFrom, &fileTo)) {
 			break;
@@ -406,9 +404,8 @@ void generateNormalizedTransitionMatrixFromFile(CooSparseMatrix *transitionMatri
 		if (fileTo > maxPageIndex) {
 			maxPageIndex = fileTo;
 		}
-		addElement(transitionMatrix, 1, fileFrom, fileTo);
+		addElement(&tempMatrix, 1, fileFrom, fileTo);
 	}
-	printf("\n");
 
 	if ((*parameters).verbose) {
 		printf("Max page index found is: %d\n", maxPageIndex);
@@ -417,15 +414,15 @@ void generateNormalizedTransitionMatrixFromFile(CooSparseMatrix *transitionMatri
 
 	// Calculates the outdegree of each page and assigns the uniform probability
 	// of transition to the elements of the corresponding row
-	int currentRow = transitionMatrix->elements[0]->rowIndex, pageOutdegree = 1;
-	for (int i=1; i<transitionMatrix->size; ++i) {
-		CooSparseMatrixElement *currentElement = transitionMatrix->elements[i];
+	int currentRow = tempMatrix.elements[0]->rowIndex, pageOutdegree = 1;
+	for (int i=1; i<tempMatrix.size; ++i) {
+		CooSparseMatrixElement *currentElement = tempMatrix.elements[i];
 		if (currentElement->rowIndex == currentRow) {
 			++pageOutdegree;
 		} else {
 			double pageUniformProbability = 1. / pageOutdegree;
 			for (int j=i-pageOutdegree; j<i; ++j) {
-				transitionMatrix->elements[j]->value = pageUniformProbability;
+				tempMatrix.elements[j]->value = pageUniformProbability;
 			}
 
 			currentRow = currentElement->rowIndex;
@@ -435,10 +432,18 @@ void generateNormalizedTransitionMatrixFromFile(CooSparseMatrix *transitionMatri
 
 	// Does the last row
 	double pageUniformProbability = 1. / pageOutdegree;
-	for (int j=transitionMatrix->size-pageOutdegree; j<transitionMatrix->size; ++j) {
-		transitionMatrix->elements[j]->value = pageUniformProbability;
+	for (int j=tempMatrix.size-pageOutdegree; j<tempMatrix.size; ++j) {
+		tempMatrix.elements[j]->value = pageUniformProbability;
 	}
 
+	// Transposes the temporary transition matrix (P^T).
+	transposeSparseMatrix(&tempMatrix);
+
+	allocMemoryForCsr(transitionMatrix, numberOfEdges);
+	// Transforms the temporary COO matrix to the desired CSR format
+	transformToCSR(tempMatrix, transitionMatrix);
+	destroyCooSparseMatrix(&tempMatrix);
+
 	fclose(graphFile);
 }
 
diff --git a/serial/serial_gs_pagerank_functions.h b/serial/serial_gs_pagerank_functions.h
index 40ed518..a9fe200 100644
--- a/serial/serial_gs_pagerank_functions.h
+++ b/serial/serial_gs_pagerank_functions.h
@@ -10,7 +10,6 @@
 #include <math.h>
 
 #include "coo_sparse_matrix.h"
-#include "lil_sparse_matrix.h"
 
 /* ===== DEFINITIONS ===== */
 
@@ -67,7 +66,7 @@ void parseArguments(int argumentCount, char **argumentVector,
 // them to populate the sparse array (transitionMatrix). The entries of the file
 // represent the edges of the web transition graph. The entries are then
 // modified to become the rows of the transition matrix.
-void generateNormalizedTransitionMatrixFromFile(CooSparseMatrix *transitionMatrix,
+void generateNormalizedTransitionMatrixFromFile(CsrSparseMatrix *transitionMatrix,
 	Parameters *parameters);
 
 // Function savePagerankToFile appends or overwrites the pagerank vector
@@ -78,14 +77,14 @@ void savePagerankToFile(char *filename, bool append, double *pagerankVector,
 // Function initialize allocates memory for the pagerank vector, reads the
 // dataset from the file and creates the transition probability distribution
 // matrix.
-void initialize(CooSparseMatrix *transitionMatrix, double **pagerankVector,
+void initialize(CsrSparseMatrix *transitionMatrix, double **pagerankVector,
 	Parameters *parameters);
 
 // Function vectorNorm calculates the first norm of a vector.
 double vectorNorm(double *vector, int vectorSize);
 
 // Function calculateNextPagerank calculates the next pagerank vector.
-void calculateNextPagerank(CooSparseMatrix *transitionMatrix,
+void calculateNextPagerank(CsrSparseMatrix *transitionMatrix,
 	double *previousPagerankVector, double **pagerankVector,
 	double *linksFromConvergedPagesPagerankVector,
 	double *convergedPagerankVector, int vectorSize, double dampingFactor);
@@ -93,7 +92,7 @@ void calculateNextPagerank(CooSparseMatrix *transitionMatrix,
 // 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(CooSparseMatrix *transitionMatrix, double **pagerankVector,
+int pagerank(CsrSparseMatrix *transitionMatrix, double **pagerankVector,
 	bool *convergenceStatus, Parameters parameters);
 
 #endif	// SERIAL_GS_PAGERANK_FUNCTIONS_H
\ No newline at end of file