Clarify the problem constraints and define the synchronization primitives (mutex + condition variables) to avoid busy-waiting. Design a state machine that tracks available H and O atoms and triggers molecule formation when thresholds are met, ensuring atomic release of actions. Then analyze safety (no invalid molecules), liveness (no deadlock/starvation), and scalability (contention, fairness) and provide pseudocode.
Pro tip: Emphasize that the solution must be deadlock-free and starvation-free; use condition variables with while loops to handle spurious wakeups and ensure that waiting threads are woken appropriately. Also, consider batching or multiple condition variables to reduce contention in high-throughput scenarios.
Restate the problem: unbounded stream, separate threads for H and O, group into H2O, no busy-waiting. Identify that actions are callable and must be released together.
Select mutex and condition variables (or semaphores) to block threads without busy-waiting. Explain why condition variables are suitable for waiting on complex conditions.
Maintain counters for available H and O atoms. When an H arrives, increment H count; if enough H and O are available, form a molecule and release actions. Similarly for O. Use a barrier-like mechanism to ensure exactly 2 H and 1 O are released together.
Safety: no molecule formed without exactly 2 H and 1 O. Liveness: no deadlock (all threads eventually proceed) and no starvation (fairness). Scalability: minimize lock contention, consider multiple condition variables or partitioning.
Write clear pseudocode using mutex and condition variables. Discuss alternative approaches (e.g., semaphores, actor model) and their trade-offs in terms of complexity and performance.
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