8th Home Work, Practical and Theoretical Questions
This commit is contained in:
@@ -2,10 +2,7 @@ import java.util.Random;
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/**
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* Simulates downloading a single chunk of a file.
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*
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* <p>This class is intentionally provided as a skeleton for students.
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* The main multithreading and simulation logic should be completed
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* in the run() method.</p>
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* Each worker writes only to its own assigned ChunkStatus object.
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*/
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public class DownloadWorker implements Runnable {
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@@ -21,23 +18,33 @@ public class DownloadWorker implements Runnable {
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@Override
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public void run() {
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// TODO: Record the chunk start time in chunkStatus.
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double downloaded = 0.0;
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// Record the start time for this chunk
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chunkStatus.setStartTimeMs(System.currentTimeMillis());
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// TODO: Print a message that this chunk has started downloading.
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double downloaded = 0.0;
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int delayRange = config.getMaxStepDelayMs() - config.getMinStepDelayMs();
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double stepRange = config.getMaxStepDownloadMB() - config.getMinStepDownloadMB();
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while (downloaded < chunkStatus.getChunkSizeMB()) {
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// TODO: Generate a random sleep delay between min and max delay.
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// TODO: Sleep for that delay.
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// TODO: Generate a random download amount for this step.
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// TODO: Increase downloaded, but do not go beyond chunk size.
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// TODO: Save the updated downloaded value into chunkStatus.
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// TODO: Optionally print step-by-step progress.
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// Random delay simulating network latency for this step
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int delay = config.getMinStepDelayMs() + (delayRange > 0 ? random.nextInt(delayRange) : 0);
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try {
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Thread.sleep(delay);
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} catch (InterruptedException e) {
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Thread.currentThread().interrupt();
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return;
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}
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// Random amount downloaded in this step, capped at remaining size
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double step = config.getMinStepDownloadMB() + random.nextDouble() * stepRange;
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downloaded = Math.min(downloaded + step, chunkStatus.getChunkSizeMB());
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// Write only to this worker's own ChunkStatus (thread-safe by design)
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chunkStatus.setDownloadedMB(downloaded);
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}
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// TODO: Mark the chunk as completed.
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// TODO: Record the chunk end time in chunkStatus.
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// TODO: Print a message that this chunk has finished downloading.
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// Mark completion and record end time
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chunkStatus.setEndTimeMs(System.currentTimeMillis());
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chunkStatus.setCompleted(true);
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}
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}
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+73
-69
@@ -3,7 +3,7 @@ import java.util.List;
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public class Main {
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public static void main(String[] args) {
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System.out.println("=== Simulated Download Manager ===");
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System.out.println("=== Simulated Download Manager ===\n");
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// 1. Read config
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DownloadConfig config;
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@@ -14,94 +14,98 @@ public class Main {
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return;
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}
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System.out.println("File name: " + config.getFileName());
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System.out.println("Total size (MB): " + config.getTotalSizeMB());
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System.out.println("Chunk count: " + config.getChunkCount());
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System.out.println("File name : " + config.getFileName());
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System.out.println("Total size : " + config.getTotalSizeMB() + " MB");
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System.out.println("Chunks : " + config.getChunkCount());
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System.out.println("Step delay : " + config.getMinStepDelayMs()
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+ "–" + config.getMaxStepDelayMs() + " ms");
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System.out.println("Step size : " + config.getMinStepDownloadMB()
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+ "–" + config.getMaxStepDownloadMB() + " MB");
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System.out.println();
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// 2. Create chunks
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// ── MULTITHREADED RUN ──────────────────────────────────────────────
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System.out.println("━━━ Multithreaded Download ━━━");
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// 2. Create chunk status objects
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List<ChunkStatus> chunks = ChunkUtils.createChunks(
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config.getTotalSizeMB(),
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config.getChunkCount()
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);
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config.getTotalSizeMB(), config.getChunkCount());
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// 3. Create worker threads
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// 3. Create one worker thread per chunk
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List<Thread> workerThreads = new ArrayList<>();
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for (ChunkStatus chunk : chunks) {
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DownloadWorker worker = new DownloadWorker(chunk, config);
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Thread workerThread = new Thread(worker, "Worker-" + chunk.getChunkId());
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workerThreads.add(workerThread);
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// TODO:
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// Students may print helpful debug information here,
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// for example which chunk is assigned to which worker thread.
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Thread t = new Thread(worker, "Worker-" + chunk.getChunkId());
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workerThreads.add(t);
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}
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// 4. Create and start monitor thread
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// 4. Create and start the monitor thread before workers so it is
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// already polling when the first worker begins
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ProgressMonitor monitor = new ProgressMonitor(config, chunks);
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Thread monitorThread = new Thread(monitor, "Progress-Monitor");
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monitorThread.start();
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// TODO:
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// Start the monitor thread before starting the workers
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// so that progress can be displayed while downloading happens.
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//
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// Example idea:
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// monitorThread.start();
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// 5. Start all worker threads
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long multiStart = System.currentTimeMillis();
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for (Thread t : workerThreads) {
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t.start();
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}
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// 5. Start worker threads
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// TODO:
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// Start each worker thread in workerThreads.
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// Use a loop and call start() on each thread.
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// 6. Wait for workers to finish
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// TODO:
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// Wait for all worker threads to complete by calling join().
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// This should be done inside a try-catch block for InterruptedException.
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//
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// Hint:
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// for (Thread thread : workerThreads) {
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// thread.join();
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// }
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// TODO:
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// After all workers finish, the monitor thread may also need to stop.
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// Depending on how ProgressMonitor is implemented, students may:
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// - wait for it to finish on its own, or
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// - add a stopping mechanism in ProgressMonitor later.
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//
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// If your monitor finishes automatically, you may join it here.
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// NOTE:
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// this final report may show 0 progress because no worker has actually run yet.
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// Until students complete the thread start/join TODOs above,
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// 6. Wait for every worker to finish before printing the final report
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try {
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for (Thread t : workerThreads) {
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t.join();
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}
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// Monitor exits on its own once it detects all chunks are done;
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// join here to make sure the final "All chunks completed" line is printed
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monitorThread.join();
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} catch (InterruptedException e) {
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Thread.currentThread().interrupt();
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System.out.println("Main thread interrupted while waiting for workers.");
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return;
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}
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long multiTime = System.currentTimeMillis() - multiStart;
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// 7. Print final report
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System.out.println();
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System.out.println("=== Final Report ===");
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int completedChunks = 0;
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double downloadedMB = 0.0;
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System.out.println("━━━ Final Report ━━━");
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int completedCount = 0;
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double totalDownloaded = 0.0;
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for (ChunkStatus chunk : chunks) {
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downloadedMB += chunk.getDownloadedMB();
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if (chunk.isCompleted()) {
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completedChunks++;
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}
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System.out.println(
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"Chunk " + chunk.getChunkId()
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+ ": " + chunk.getDownloadedMB()
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+ "/" + chunk.getChunkSizeMB()
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+ " MB"
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);
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totalDownloaded += chunk.getDownloadedMB();
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if (chunk.isCompleted()) completedCount++;
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System.out.printf(" Chunk #%d : %.1f / %.1f MB (%.2fs)%n",
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chunk.getChunkId(),
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chunk.getDownloadedMB(),
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chunk.getChunkSizeMB(),
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chunk.getDownloadDurationMs() / 1000.0);
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}
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System.out.printf(" Completed : %d / %d chunks%n", completedCount, chunks.size());
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System.out.printf(" Downloaded: %.1f / %.1f MB%n",
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totalDownloaded, (double) config.getTotalSizeMB());
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System.out.printf(" Wall time : %.2f seconds%n%n", multiTime / 1000.0);
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// ── SEQUENTIAL RUN (Bonus – comparison) ───────────────────────────
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System.out.println("━━━ Sequential Download (Bonus Comparison) ━━━");
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List<ChunkStatus> seqChunks = ChunkUtils.createChunks(
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config.getTotalSizeMB(), config.getChunkCount());
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long seqTime = SequentialDownloader.run(config, seqChunks);
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// ── COMPARISON REPORT ──────────────────────────────────────────────
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System.out.println();
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System.out.println("Completed chunks: " + completedChunks + "/" + chunks.size());
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System.out.println("Downloaded total: " + downloadedMB + "/" + config.getTotalSizeMB() + " MB");
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System.out.println("━━━ Performance Comparison ━━━");
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System.out.printf(" Sequential : %.2f seconds%n", seqTime / 1000.0);
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System.out.printf(" Multithreaded : %.2f seconds%n", multiTime / 1000.0);
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System.out.printf(" Speedup : %.2fx%n", (double) seqTime / Math.max(multiTime, 1));
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System.out.println();
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System.out.println(" Analysis:");
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System.out.println(" In the multithreaded run each worker sleeps independently,");
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System.out.println(" so all network-latency delays overlap in parallel.");
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System.out.println(" The sequential run must wait for each chunk in turn,");
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System.out.println(" making the total time roughly N × (average chunk time).");
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System.out.println();
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System.out.println("Simulation finished.");
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}
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}
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@@ -1,5 +1,17 @@
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import java.util.ArrayDeque;
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import java.util.Deque;
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import java.util.List;
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/**
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* Monitors and displays real-time download progress for all chunks.
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*
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* Bonus features implemented:
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* - Real-time in-place progress bar using ANSI escape codes
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* - Per-chunk progress bars with completion indicators
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* - Overall download speed (MB/s) calculation
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* - Estimated Time of Arrival (ETA) calculation
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* - Event log showing chunk start/finish events
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*/
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public class ProgressMonitor implements Runnable {
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private final String fileName;
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@@ -7,57 +19,87 @@ public class ProgressMonitor implements Runnable {
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private final List<ChunkStatus> chunks;
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private final long monitorDelayMs;
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// Event detection: track previous state to detect chunk start/finish
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private final boolean[] wasStarted;
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private final boolean[] wasCompleted;
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private final Deque<String> eventLog = new ArrayDeque<>();
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private static final int MAX_LOG_ENTRIES = 5;
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// Speed and ETA tracking
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private double previousTotalMB = 0.0;
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private long previousTimeMs;
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// In-place ANSI update tracking
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private int lastPrintedLines = 0;
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// ANSI escape codes
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private static final String RESET = "\033[0m";
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private static final String BOLD = "\033[1m";
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private static final String DIM = "\033[2m";
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private static final String GREEN = "\033[92m";
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private static final String CYAN = "\033[96m";
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private static final String YELLOW = "\033[93m";
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private static final String CLEAR_LINE = "\033[2K";
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private static final int BAR_WIDTH = 30;
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public ProgressMonitor(DownloadConfig config, List<ChunkStatus> chunks) {
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this.fileName = config.getFileName();
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this.totalSizeMB = config.getTotalSizeMB();
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this.chunks = chunks;
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this.monitorDelayMs = 500;
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this.previousTimeMs = System.currentTimeMillis();
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this.wasStarted = new boolean[chunks.size()];
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this.wasCompleted = new boolean[chunks.size()];
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}
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@Override
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public void run() {
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// TODO:
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// Repeatedly check chunk progress until all chunks are completed.
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// In each loop:
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// 1. Read the downloaded size from every chunk
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// 2. Add all downloaded amounts to totalDownloadedMB
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// 3. Count completed chunks
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// 4. Print a progress message
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// 5. If completedChunks == chunks.size(), print a final monitor message and stop
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// 6. Otherwise sleep for monitorDelayMs and continue
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boolean firstPrint = true;
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while (true) {
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double totalDownloadedMB = 0.0;
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int completedChunks = 0;
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for (ChunkStatus chunk : chunks) {
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// 1. Read progress from every chunk and detect state-change events
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for (int i = 0; i < chunks.size(); i++) {
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ChunkStatus chunk = chunks.get(i);
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totalDownloadedMB += chunk.getDownloadedMB();
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if (chunk.isCompleted()) completedChunks++;
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if (chunk.isCompleted()) {
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completedChunks++;
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if (!wasStarted[i] && chunk.getStartTimeMs() > 0) {
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wasStarted[i] = true;
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addEvent(String.format("Chunk #%d started (%.0f MB)",
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chunk.getChunkId(), chunk.getChunkSizeMB()));
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}
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if (!wasCompleted[i] && chunk.isCompleted()) {
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wasCompleted[i] = true;
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addEvent(String.format("Chunk #%d finished (%.2fs)",
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chunk.getChunkId(), chunk.getDownloadDurationMs() / 1000.0));
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}
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}
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double percent = 0.0;
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if (totalSizeMB > 0) {
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percent = (totalDownloadedMB * 100.0) / totalSizeMB;
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// 2. Calculate speed and ETA
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long now = System.currentTimeMillis();
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double elapsed = (now - previousTimeMs) / 1000.0;
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double speed = elapsed > 0.001 ? (totalDownloadedMB - previousTotalMB) / elapsed : 0.0;
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double remaining = totalSizeMB - totalDownloadedMB;
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double eta = (speed > 0.01) ? remaining / speed : -1.0;
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previousTotalMB = totalDownloadedMB;
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previousTimeMs = now;
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// 3. Build and print the real-time dashboard
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String dashboard = buildDashboard(totalDownloadedMB, completedChunks, speed, eta);
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printInPlace(dashboard, firstPrint);
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firstPrint = false;
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// 5. Exit gracefully once all chunks are done
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if (completedChunks == chunks.size()) {
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System.out.println(BOLD + GREEN + " All chunks completed! Download finished." + RESET);
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break;
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}
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System.out.printf(
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"Progress for %s: %.1f/%.1f MB (%.2f%%), completed chunks: %d/%d%n",
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fileName,
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totalDownloadedMB,
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(double) totalSizeMB,
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percent,
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completedChunks,
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chunks.size()
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);
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// TODO:
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// If all chunks are completed, print a final message and exit the loop
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// 6. Sleep before the next polling cycle
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try {
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Thread.sleep(monitorDelayMs);
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} catch (InterruptedException e) {
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@@ -66,4 +108,86 @@ public class ProgressMonitor implements Runnable {
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}
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}
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}
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private void addEvent(String message) {
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if (eventLog.size() >= MAX_LOG_ENTRIES) eventLog.pollFirst();
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eventLog.addLast(message);
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}
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/**
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* Overwrites the previous dashboard in-place using ANSI cursor-up sequences,
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* producing a smooth real-time update instead of scrolling output.
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*/
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private void printInPlace(String dashboard, boolean firstPrint) {
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if (!firstPrint && lastPrintedLines > 0) {
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// Move cursor up to the top of the previous dashboard
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System.out.printf("\033[%dA", lastPrintedLines);
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}
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String[] lines = dashboard.split("\n", -1);
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for (String line : lines) {
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System.out.print(CLEAR_LINE + line + "\n");
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}
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System.out.flush();
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lastPrintedLines = lines.length;
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}
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private String buildDashboard(double totalMB, int completedChunks, double speed, double eta) {
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StringBuilder sb = new StringBuilder();
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String divider = " " + "─".repeat(54);
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sb.append(BOLD).append(CYAN)
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.append(" ┌─ Download Manager ─ ").append(fileName).append("\n")
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.append(RESET);
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// Per-chunk progress rows
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for (ChunkStatus chunk : chunks) {
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sb.append(chunkLine(chunk)).append("\n");
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}
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sb.append(DIM).append(divider).append(RESET).append("\n");
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// Overall progress bar
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double pct = totalSizeMB > 0 ? totalMB / totalSizeMB * 100.0 : 0.0;
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sb.append(String.format(" " + BOLD + "Total " + RESET + " %s %5.1f%% %.1f / %.0f MB\n",
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colorBar(pct, BAR_WIDTH), pct, totalMB, (double) totalSizeMB));
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// Speed and ETA line
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if (speed > 0.01) {
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String etaStr = eta >= 0 ? String.format("%.1fs", eta) : "∞";
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sb.append(String.format(" " + YELLOW + "Speed: %.2f MB/s" + RESET
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+ " ETA: %-8s chunks: %d / %d\n",
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speed, etaStr, completedChunks, chunks.size()));
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} else {
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sb.append(String.format(" Warming up… chunks: %d / %d\n",
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completedChunks, chunks.size()));
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}
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// Event log
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if (!eventLog.isEmpty()) {
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sb.append(DIM).append(divider).append(RESET).append("\n");
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for (String event : eventLog) {
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sb.append(DIM).append(" » ").append(event).append(RESET).append("\n");
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}
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}
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// Remove trailing newline so split gives the right count
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String result = sb.toString();
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if (result.endsWith("\n")) result = result.substring(0, result.length() - 1);
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return result;
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}
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private String chunkLine(ChunkStatus chunk) {
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double pct = chunk.getProgressPercentage();
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String tick = chunk.isCompleted() ? GREEN + "✓" + RESET : " ";
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return String.format(" [%s] Chunk #%d %s %5.1f%%",
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tick, chunk.getChunkId(), colorBar(pct, BAR_WIDTH), pct);
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}
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/** Renders a Unicode block-character progress bar with ANSI colour. */
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private String colorBar(double percent, int width) {
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int filled = (int) Math.round(percent / 100.0 * width);
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filled = Math.max(0, Math.min(filled, width));
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return GREEN + "█".repeat(filled) + RESET
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+ DIM + "░".repeat(width - filled) + RESET;
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}
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}
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||||
@@ -0,0 +1,32 @@
|
||||
import java.util.List;
|
||||
|
||||
/**
|
||||
* Bonus Task – Sequential vs Multithreaded Comparison.
|
||||
*
|
||||
* Downloads all chunks one after another on the calling thread.
|
||||
* This exists only for timing comparison with the multithreaded run;
|
||||
* it demonstrates the speedup gained from parallel execution.
|
||||
*/
|
||||
public class SequentialDownloader {
|
||||
|
||||
private SequentialDownloader() {}
|
||||
|
||||
/**
|
||||
* Runs each chunk sequentially on the current thread and returns
|
||||
* the total elapsed time in milliseconds.
|
||||
*/
|
||||
public static long run(DownloadConfig config, List<ChunkStatus> chunks) {
|
||||
long start = System.currentTimeMillis();
|
||||
|
||||
for (ChunkStatus chunk : chunks) {
|
||||
System.out.printf("[Sequential] Chunk #%d starting (%.0f MB)%n",
|
||||
chunk.getChunkId(), chunk.getChunkSizeMB());
|
||||
DownloadWorker worker = new DownloadWorker(chunk, config);
|
||||
worker.run(); // blocks until this chunk is fully "downloaded"
|
||||
System.out.printf("[Sequential] Chunk #%d done in %.2fs%n",
|
||||
chunk.getChunkId(), chunk.getDownloadDurationMs() / 1000.0);
|
||||
}
|
||||
|
||||
return System.currentTimeMillis() - start;
|
||||
}
|
||||
}
|
||||
Reference in New Issue
Block a user