thread_pool_example.cc File Reference

Comprehensive ThreadPool Usage Examples: Parallel Task Execution. More...

#include <thread_pool.H>
#include <iostream>
#include <iomanip>
#include <vector>
#include <cmath>
#include <chrono>
#include <fstream>
#include <sstream>

Include dependency graph for thread_pool_example.cc:

Go to the source code of this file.

Classes
struct	FileResult

Functions
void	print_header (const std::string &title)
bool	is_prime (int n)
void	example_basic_parallel ()
FileResult	process_file (const std::string &filename)
void	example_batch_processing ()
void	example_fire_and_forget ()
void	example_backpressure ()
void	example_load_shedding ()
void	example_performance ()
int	main ()

Detailed Description

Comprehensive ThreadPool Usage Examples: Parallel Task Execution.

This file demonstrates how to use the ThreadPool class effectively for parallel task execution. ThreadPool provides a high-level interface for managing worker threads and executing tasks concurrently, making it easier to parallelize computations.

What is a Thread Pool?

A thread pool is a collection of worker threads that execute tasks from a queue. Instead of creating threads for each task, threads are reused, reducing overhead and improving performance.

Benefits:

• Reduced overhead: Reuse threads instead of creating/destroying
• Resource control: Limit number of concurrent threads
• Task queuing: Handle more tasks than threads
• Load balancing: Distribute work across threads

Features Demonstrated

Example 1: Basic Parallel Computation

• **enqueue()**: Submit task and get future
• Futures: Wait for results asynchronously
• Basic pattern: Most common usage

Example 2: Batch Processing

• **enqueue_bulk()**: Process collections in parallel
• Batch operations: Efficient parallel processing
• Collection handling: Work with containers

Example 3: Fire-and-Forget Tasks

• **enqueue_detached()**: Submit without waiting
• Async operations: Don't need results
• Background tasks: Long-running operations

Example 4: Backpressure Control

• **enqueue_bounded()**: Limit queue size
• Flow control: Prevent queue overflow
• Backpressure: Handle overload gracefully

Example 5: Non-Blocking Submission

• **try_enqueue()**: Submit without blocking
• Load shedding: Reject when overloaded
• Non-blocking: Don't wait if queue full

Example 6: Performance Comparison

• Benchmarking: Compare parallel vs sequential
• Speedup: Measure performance gains
• Scalability: Test with different thread counts

Quick Start

// Create thread pool with 4 worker threads
ThreadPool pool(4);
 
// Submit a task and get a future
auto future = pool.enqueue([](int x) { return x * x; }, 5);
 
// Wait for result
int result = future.get();  // result = 25

When to Use ThreadPool

✅ Good for:

• CPU-intensive tasks
• Independent computations
• Batch processing
• Parallel algorithms

❌ Not good for:

• I/O-bound tasks (use async I/O)
• Very short tasks (overhead too high)
• Tasks with dependencies (use task graphs)

Complexity

Operation	Complexity	Notes
enqueue()	O(1) amortized	Queue insertion
Future.get()	O(1)	Wait for completion
Thread creation	O(1)	Done at pool creation

Performance Considerations

• Thread count: Usually CPU cores - 1 or CPU cores
• Task granularity: Tasks should be substantial (avoid tiny tasks)
• Overhead: ThreadPool has overhead, measure before optimizing
• Cache effects: Consider data locality

Usage

./thread_pool_example

This example has no command-line options; it runs all examples.

Compilation

g++ -std=c++20 -O2 -pthread -I.. thread_pool_example.cc -o thread_pool_example

Or using CMake:

cmake --build . --target thread_pool_example

See also

thread_pool.H ThreadPool class implementation

ah_parallel_example.cc Parallel functional programming (uses ThreadPool)

Author

Leandro Rabindranath León

Definition in file thread_pool_example.cc.

Function Documentation

example_backpressure()

void example_backpressure

(

)

Definition at line 368 of file thread_pool_example.cc.

References Aleph::ThreadPool::enqueue_bounded_detached(), Aleph::ThreadPool::get_queue_limits(), Aleph::maps(), Aleph::ThreadPool::pending_tasks(), print_header(), Aleph::ThreadPool::set_queue_limits(), and Aleph::ThreadPool::wait_all().

Referenced by main().

example_basic_parallel()

void example_basic_parallel

(

)

Definition at line 168 of file thread_pool_example.cc.

References Aleph::ThreadPool::enqueue(), is_prime(), Aleph::maps(), Aleph::ThreadPool::num_threads(), print_header(), and Aleph::HTList::size().

Referenced by main().

example_batch_processing()

void example_batch_processing

(

)

Definition at line 258 of file thread_pool_example.cc.

References Aleph::ThreadPool::enqueue_bulk(), Aleph::DynList< T >::get(), Aleph::maps(), Aleph::ThreadPool::num_threads(), print_header(), process_file(), and Aleph::HTList::size().

Referenced by main().

example_fire_and_forget()

void example_fire_and_forget

(

)

Definition at line 322 of file thread_pool_example.cc.

References Aleph::ThreadPool::enqueue_detached(), Aleph::maps(), print_header(), and Aleph::ThreadPool::wait_all().

Referenced by main().

example_load_shedding()

void example_load_shedding

(

)

Definition at line 446 of file thread_pool_example.cc.

References Aleph::maps(), print_header(), Aleph::ThreadPool::set_queue_limits(), Aleph::ThreadPool::try_enqueue_detached(), and Aleph::ThreadPool::wait_all().

Referenced by main().

example_performance()

void example_performance

(

)

Definition at line 499 of file thread_pool_example.cc.

References Aleph::ThreadPool::enqueue(), Aleph::DynList< T >::get(), Aleph::maps(), Aleph::ThreadPool::num_threads(), and print_header().

Referenced by main().

is_prime()

bool is_prime

(

int

n

)

Definition at line 158 of file thread_pool_example.cc.

Referenced by example_basic_parallel(), and example_parallel_filter().

main()

int main

(

)

Definition at line 566 of file thread_pool_example.cc.

References example_backpressure(), example_basic_parallel(), example_batch_processing(), example_fire_and_forget(), example_load_shedding(), and example_performance().

print_header()

void print_header

(

const std::string &

title

)

Definition at line 133 of file thread_pool_example.cc.

References Aleph::maps().

process_file()

FileResult process_file

(

const std::string &

filename

)

Definition at line 244 of file thread_pool_example.cc.

References Aleph::maps().

Referenced by example_batch_processing().