hw5 start

Homeworks/hw5/SeanRettigHW5.tex

@@ -6,7 +6,7 @@
 \usepackage[a4paper, total={6in, 8in}]{geometry}
 \usepackage{graphicx}
 
-\title{CS 448 Spring 2024 Homework 1}
+\title{CS 448 Spring 2024 Homework 5}
 \author{Sean Rettig}
 
 \begin{document}

Projects/cs448p4/.gitignore

@@ -0,0 +1,23 @@
+bin/
+.DS_Store
+sean.minibase
+
+# ---> Maven
+target/
+pom.xml.tag
+pom.xml.releaseBackup
+pom.xml.versionsBackup
+pom.xml.next
+release.properties
+dependency-reduced-pom.xml
+buildNumber.properties
+.mvn/timing.properties
+# https://github.com/takari/maven-wrapper#usage-without-binary-jar
+.mvn/wrapper/maven-wrapper.jar
+
+# Eclipse m2e generated files
+# Eclipse Core
+.project
+# JDT-specific (Eclipse Java Development Tools)
+.classpath
+

Projects/cs448p4/src/main/java/CC/CC.java

@@ -1,25 +1,418 @@
 package CC;
-import java.util.List;
 
-public class CC
-{
+import java.util.List;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.Iterator;
+import java.util.LinkedList;
+import java.util.Queue;
+
+enum LockState {
+	NONE,
+	SHARED,
+	EXCLUSIVE
+}
+
+class Lock {
+
+	private ArrayList<Integer> transactionIds;
+	private LockState type;
+	private int noReads;
+
+	public Lock() {
+		this.transactionIds = new ArrayList<Integer>();
+		this.noReads = 0;
+		this.type = LockState.NONE;
+	}
+
+	public ArrayList<Integer> getTransactionIds() {
+		return transactionIds;
+	}
+
+	public void addTransactionId(int transactionId) {
+		if (!transactionIds.contains(Integer.valueOf(transactionId))) {
+			transactionIds.add(transactionId);
+			noReads++;
+		}
+	}
+
+	public LockState getType() {
+		return type;
+	}
+
+	public void setType(LockState type) {
+		this.type = type;
+	}
+
+	public int getNoReads() {
+		return noReads;
+	}
+
+	public boolean hasLock(int transactionId) {
+		return transactionIds.contains(Integer.valueOf(transactionId));
+	}
+
+	public void release(int releaseTransactionId) {
+		transactionIds.remove(Integer.valueOf(releaseTransactionId));
+		noReads--;
+
+		if (noReads == 0) {
+			this.type = LockState.NONE;
+		}
+	}
+}
+
+class LockTable {
+	private Lock[] locks;
+	private static final int NUM_RECORDS = 10;
+
+	public LockTable() {
+		this.locks = new Lock[NUM_RECORDS];
+		// initialize the locktable
+		for (int recordId = 0; recordId < NUM_RECORDS; recordId++) {
+			locks[recordId] = new Lock();
+		}
+	}
+
+	public Lock getLock(int recordId) {
+		if (recordId >= 0 && recordId < locks.length) {
+			return locks[recordId];
+		} else {
+			throw new IllegalArgumentException("Invalid recordId: " + recordId);
+		}
+	}
+
+	public void releaseLocksForTransaction(int[] recordIds, int transactionId) {
+		for (int recordId : recordIds) {
+			if (recordId >= 0 && recordId < locks.length) {
+				locks[recordId].release(transactionId);
+			} else {
+				throw new IllegalArgumentException("Invalid recordId: " + recordId);
+			}
+		}
+	}
+}
+
+interface Operation {
+	int getRecordId();
+
+	int getValue();
+}
+
+class WriteOp implements Operation {
+	private int recordId;
+	private int value;
+
+	public WriteOp(int recordId, int value) {
+		this.recordId = recordId;
+		this.value = value;
+	}
+
+	public int getRecordId() {
+		return recordId;
+	}
+
+	public int getValue() {
+		return value;
+	}
+}
+
+class ReadOp implements Operation {
+	private int recordId;
+
+	public ReadOp(int recordId) {
+		this.recordId = recordId;
+	}
+
+	public int getRecordId() {
+		return recordId;
+	}
+
+	public int getValue() {
+		return -1;
+	}
+}
+
+class CommitOp implements Operation {
+	public int getRecordId() {
+		return -1;
+	}
+
+	public int getValue() {
+		return -1;
+	}
+}
+
+class Transaction {
+	private int currentOperationIndex;
+	private Operation[] operations;
+	private int transactionId;
+	private ArrayList<Integer> recordLocks;
+	private int prevTimestamp;
+	private boolean aborted;
+
+	public Transaction(String[] operations, int transactionId) {
+		this.currentOperationIndex = 0;
+		this.operations = new Operation[operations.length];
+		this.transactionId = transactionId;
+		this.recordLocks = new ArrayList<Integer>();
+		this.prevTimestamp = -1;
+		this.aborted = false;
+
+		int OpIndex = 0;
+
+		for (String operation : operations) {
+			if (operation.charAt(0) == 'W') {
+				this.operations[OpIndex] = new WriteOp(Character.getNumericValue(operation.charAt(2)),
+						Character.getNumericValue(operation.charAt(4)));
+			} else if (operation.charAt(0) == 'R') {
+				this.operations[OpIndex] = new ReadOp(Character.getNumericValue(operation.charAt(2)));
+			} else {
+				this.operations[OpIndex] = new CommitOp();
+			}
+			OpIndex++;
+		}
+	}
+
+	public int getCurrentOperationIndex() {
+		return currentOperationIndex;
+	}
+
+	public int getTransactionId() {
+		return transactionId;
+	}
+
+	public void setCurrentOperationIndex(int currentOperationIndex) {
+		this.currentOperationIndex = currentOperationIndex;
+	}
+
+	public Operation[] getOperations() {
+		return operations;
+	}
+
+	public boolean hasNextOperation() {
+		return (currentOperationIndex < operations.length) && !aborted;
+	}
+
+	public int doNextOperation(LockTable lockTable, int[] database, ArrayList<String[]> systemLog, int timestamp,
+			LinkedList<Integer>[] adj) {
+		if (hasNextOperation() && !aborted) {
+			Operation nextOp = operations[currentOperationIndex];
+			Lock nextLock = null;
+			if (!(nextOp instanceof CommitOp)) {
+				nextLock = lockTable.getLock(nextOp.getRecordId());
+			}
+			currentOperationIndex++;
+
+			if (nextOp instanceof ReadOp) {
+				if (!(nextLock.hasLock(transactionId))) {
+					// The current transaction doesn't already have the lock.
+					if (nextLock.getType() == LockState.EXCLUSIVE) {
+						currentOperationIndex--;
+						for (int adjTransactionId : nextLock.getTransactionIds()) {
+							if (adjTransactionId != transactionId
+									&& !adj[transactionId].contains(Integer.valueOf(adjTransactionId))) {
+								adj[transactionId].add(adjTransactionId);
+							}
+						}
+						return timestamp;
+						// The lock on the record is exclusive.
+					} else {
+						nextLock.setType(LockState.SHARED);
+						nextLock.addTransactionId(transactionId);
+						recordLocks.add(nextOp.getRecordId());
+					}
+				}
+				String[] log = { "R", Integer.toString(timestamp), "T" + Integer.toString(transactionId),
+						Integer.toString(nextOp.getRecordId()), Integer.toString(database[nextOp.getRecordId()]),
+						Integer.toString(prevTimestamp) };
+				systemLog.add(log);
+
+			} else if (nextOp instanceof WriteOp) {
+				int prevValue = database[nextOp.getRecordId()];
+				if ((nextLock.hasLock(transactionId) && nextLock.getNoReads() == 1)
+						|| nextLock.getType() == LockState.NONE) {
+					nextLock.setType(LockState.EXCLUSIVE);
+					database[nextOp.getRecordId()] = nextOp.getValue();
+					nextLock.addTransactionId(transactionId);
+
+					if (!recordLocks.contains(Integer.valueOf(nextOp.getRecordId()))) {
+						recordLocks.add(nextOp.getRecordId());
+					}
+
+				} else {
+					currentOperationIndex--;
+					for (int adjTransactionId : nextLock.getTransactionIds()) {
+						if (adjTransactionId != transactionId
+								&& !adj[transactionId].contains(Integer.valueOf(adjTransactionId))) {
+							adj[transactionId].add(adjTransactionId);
+						}
+					}
+					return timestamp;
+				}
+				String[] log = { "W", Integer.toString(timestamp), "T" + Integer.toString(transactionId),
+						Integer.toString(nextOp.getRecordId()), Integer.toString(prevValue),
+						Integer.toString(database[nextOp.getRecordId()]),
+						Integer.toString(prevTimestamp) };
+				systemLog.add(log);
+
+			} else {
+				for (int recordLock : recordLocks) {
+					lockTable.getLock(recordLock).release(transactionId);
+				}
+				recordLocks = new ArrayList<Integer>();
+
+				String[] log = { "C", Integer.toString(timestamp), "T" + Integer.toString(transactionId),
+						Integer.toString(prevTimestamp) };
+				systemLog.add(log);
+			}
+
+			prevTimestamp = timestamp;
+			timestamp++;
+		}
+
+		return timestamp;
+	}
+
+	public void reset() {
+		currentOperationIndex = 0;
+		recordLocks = new ArrayList<Integer>();
+	}
+
+	public int abortTransaction(LockTable lockTable, int[] database, ArrayList<String[]> systemLog, int timestamp,
+			LinkedList<Integer>[] adj) {
+		aborted = true;
+		int pastTransaction = prevTimestamp;
+
+		do {
+			String[] lastLog = systemLog.get(pastTransaction);
+			if (lastLog[0] == "W") {
+				database[Integer.parseInt(lastLog[3])] = Integer.parseInt(lastLog[4]);
+			}
+			pastTransaction = Integer.parseInt(lastLog[lastLog.length - 1]);
+		} while (pastTransaction != -1);
+
+		for (int recordLock : recordLocks) {
+			lockTable.getLock(recordLock).release(transactionId);
+		}
+		recordLocks = new ArrayList<Integer>();
+
+		adj[transactionId] = new LinkedList<Integer>();
+
+		String[] log = { "A", Integer.toString(timestamp), "T" + Integer.toString(transactionId),
+				Integer.toString(prevTimestamp) };
+		systemLog.add(log);
+
+		return -1;
+	}
+}
+
+public class CC {
+	private static final int NUM_RECORDS = 10;
 
 	/**
 	 * Notes:
-	 *  - Execute all given transactions, using locking.
-	 *  - Each element in the transactions List represents all operations performed by one transaction, in order.
-	 *  - No operation in a transaction can be executed out of order, but operations may be interleaved with other
-	 *    transactions if allowed by the locking.
-	 *  - The index of the transaction in the list is equivalent to the transaction ID.
-	 *  - Print the log to the console at the end of the method.
-	 *  - Return the new db state after executing the transactions.
-	 * @param db the initial status of the db
-	 * @param transactions the schedule, which basically is a {@link List} of transactions.
+	 * - Execute all given transactions, using locking.
+	 * - Each element in the transactions List represents all operations performed
+	 * by one transaction, in order.
+	 * - No operation in a transaction can be executed out of order, but operations
+	 * may be interleaved with other
+	 * transactions if allowed by the locking.
+	 * - The index of the transaction in the list is equivalent to the transaction
+	 * ID.
+	 * - Print the log to the console at the end of the method.
+	 * - Return the new db state after executing the transactions.
+	 * 
+	 * @param db           the initial status of the db
+	 * @param transactions the schedule, which basically is a {@link List} of
+	 *                     transactions.
 	 * @return the final status of the db
 	 */
-	public static int[] executeSchedule(int[] db, List<String> transactions)
-	{
-		//TODO
-		return null ;
+	public static int[] executeSchedule(int[] db, List<String> transactions) {
+		LockTable lockTable = new LockTable();
+		Queue<Transaction> transactionQueue = new LinkedList<>();
+		Transaction[] transactionsArray = new Transaction[transactions.size() + 1];
+		int newTransactionId = 1;
+		int[] database = new int[NUM_RECORDS];
+		ArrayList<String[]> systemLog = new ArrayList<>();
+		int timestamp = 0;
+
+		LinkedList<Integer>[] adj;
+
+		for (int i = 0; i < NUM_RECORDS; i++) {
+			database[i] = i;
+		}
+
+		for (String transaction : transactions) {
+			Transaction newTransaction = new Transaction(transaction.split(";"), newTransactionId);
+			transactionQueue.add(newTransaction);
+			transactionsArray[newTransactionId] = newTransaction;
+			newTransactionId++;
+		}
+		adj = new LinkedList[transactions.size() + 1];
+		for (int i = 0; i < transactions.size() + 1; ++i) {
+			adj[i] = new LinkedList<Integer>();
+		}
+
+		while (!transactionQueue.isEmpty()) {
+			Transaction curTransaction = transactionQueue.remove();
+			if (curTransaction.hasNextOperation()) {
+				timestamp = curTransaction.doNextOperation(lockTable, database, systemLog, timestamp, adj);
+
+				// Here is where we check if there are deadlocks. We run DFS.
+				boolean[] visited = new boolean[transactions.size() + 1];
+				int[] predecessor = new int[transactions.size() + 1];
+				ArrayList<Integer> nodesInCycle = DFS(curTransaction.getTransactionId(), visited, adj, predecessor);
+
+				if (nodesInCycle != null) {
+					Collections.sort(nodesInCycle);
+					transactionsArray[nodesInCycle.get(nodesInCycle.size() - 1)].abortTransaction(lockTable, database,
+							systemLog, timestamp,
+							adj);
+					timestamp++;
+				}
+
+				transactionQueue.add(curTransaction);
+			}
+		}
+
+		for (String[] log : systemLog) {
+			StringBuilder sb = new StringBuilder(log[0] + ":" + log[1]);
+			for (int k = 2; k < log.length; k++) {
+				sb.append("," + log[k]);
+			}
+			System.out.println(sb.toString());
+		}
+		System.out.println();
+
+		return database;
+	}
+
+	public static ArrayList<Integer> DFS(int v, boolean visited[], LinkedList<Integer> adj[], int predecessor[]) {
+		visited[v] = true;
+
+		Iterator<Integer> i = adj[v].listIterator();
+		while (i.hasNext()) {
+			int n = i.next();
+			if (!visited[n]) {
+				predecessor[n] = v;
+				return DFS(n, visited, adj, predecessor);
+			} else {
+				return returnNodesInCycle(predecessor, v, n);
+			}
+		}
+		return null;
+	}
+
+	public static ArrayList<Integer> returnNodesInCycle(int[] predecessor, int parent, int start) {
+		ArrayList<Integer> nodesInCycle = new ArrayList<>();
+		nodesInCycle.add(parent);
+		nodesInCycle.add(start);
+
+		while (predecessor[start] != parent && predecessor[start] != 0) {
+			nodesInCycle.add(predecessor[start]);
+			start = predecessor[start];
+		}
+		return nodesInCycle;
 	}
 }