Lesson 47 of 55
10 mins readPython Concurrency, forkIO & MVars
In Plain English
GHC includes ultra-lightweight green threads scheduled across CPU cores. Spawn threads with forkIO and communicate safely using synchronized MVar memory cells.
Deep Dive: How It Works
Green Threads (forkIO): GHC threads take only ~1KB of memory, allowing millions of concurrent threads.
MVar: A synchronized mutable location that is either empty or full. takeMVar blocks until full; putMVar blocks until empty.
Software Transactional Memory (STM): Atomic, composable memory transactions using atomically and TVars.
Core Rules to Remember
Lightweight Threads (forkIO): Spawn tens of thousands of concurrent green threads with minimal overhead.
MVar Synchronization: Thread-safe lock-free communication primitive.
Live Interactive Example
Hit Run Code to see it liveMVar Synchronization Between Threads
Python 3.12
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Output Console
Click "Run Code" to view the rendered output.
How it works: takeMVar blocked until the worker thread populated the MVar.
Your Turn: Micro Challenge
No pressure! Edit the starter code below and test your solution with instant feedback.
Micro Exercise
Put and Take MVar in Sequence
- Create an empty MVar, put `"Ready"`, and take it.
- Print `"Status: "` followed by the extracted value.
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Sandbox Output
Click "Run & Check" to test your solution.
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