Concurrent Programming

Concurrent programming writes code that correctly executes multiple tasks whose operations overlap in time. It addresses thread management, locks, atomic operations, message passing, and the patterns that prevent data races and deadlocks in shared-memory and distributed systems.

itSoftware engineering

Concurrent Programming

Concurrent programming lets a program make progress on more than one task during the same period. The tasks may alternate on one processor core or run at the same instant on several cores. That distinction matters: concurrency is about structure, while parallelism is about simultaneous execution.

You use concurrency whenever work can overlap. A server handles one request while another waits for storage. A desktop application keeps its interface responsive during a download. A data pipeline processes independent partitions at once. The goal may be responsiveness, throughput, resource use, or a clear model for many activities in flight.

Concurrency also removes a useful assumption. In sequential code, one operation finishes before the next begins. In concurrent code, a scheduler may interleave operations in many valid orders. Your design must remain correct across every allowed order, not only the order you happened to observe in a test.

The execution building blocks

A process is a running program with its own resources and address space. A thread is a flow of control inside a process. Threads in one process normally share memory. A task is a unit of work submitted to a runtime or executor; the runtime decides which thread or process runs it. A coroutine is a function that can suspend and later resume, often on the same thread as other coroutines.

These abstractions solve different problems:

Threads support preemptive concurrency and shared memory.
Processes isolate memory and failures more strongly, but communication costs more.
Tasks separate the work you want done from the workers that execute it.
Coroutines make large numbers of waiting operations practical through cooperative suspension.

Concurrent Programming

The execution building blocks

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