Notes: Computation

Parallel vs Concurrent

Parallel

Multi core, multiple tasks happening at a single point in time.

Concurrent

Single core, quickly switching between multiple tasks where only one task is happening at a single point in time.

Bottlenecks

CPU Bound

CPU is working through the problem.

I/O Bound

CPU is waiting for the data.

Threads (Concurrency)

Native Threads (1:1)

1 app thread = 1 OS thread.

Green Threads (N:M)

Several virtual threads map to a pool of OS threads.

Efficiency != Performance

Efficiency with Algorithms, Performance with Data Structures - Chandler Carruth

Efficiency = Algorithms

Efficiency is doing less work to get the same result.

Performance = Data Structures

Data Structures allow the CPU pipeline to perform better.

Message Passing

Queue

n=5, bounded, buffered, asynchronous

Future / Promise

n=1, bounded, buffered, asynchronous

Channels, Actor model

n=0, bounded, unbuffered, synchronous