amdahl

Threads look deceptively simple — create a few, share some memory, done. In practice, shared mutable state is a minefield: race conditions, non-deterministic output, and bugs that vanish under a debugger. This lesson dissects concurrency vs parallelism, why `count++` is three operations the CPU can interleave, Amdahl's law, and what a critical section actually means.

Why GPUs eat CPUs for breakfast on some workloads and choke on others. Serial vs parallel execution, Amdahl's law, the latency-vs-throughput trade-off baked into silicon, and a rule of thumb for when to reach for a GPU.