JavaScript Concurrency by Unknown

Author:Unknown
Language: eng
Format: mobi, epub, pdf
Publisher: Packt Publishing

Note

What happens when our code runs in the main thread just as often as it runs in a worker thread? Does this mean that we have to write our task code twice: once for sequential code and again for our workers? We obviously want to avoid this, so we need to keep our task code modular. It needs to be usable both in the main thread and worker threads.

Hardware concurrency capabilities

Another high-level check that we'll perform in our concurrent applications is the concurrency capabilities of the hardware that we're running on. This informs us how many web workers to create. For example, there's really nothing for us to gain by creating 32 web workers on a system where there are only four CPU cores. On this system, four web workers would be more appropriate. So, how do we get this number?

Let's create a generic function that figures this out for us:

// Returns the the ideal number of web workers // to create. function getConcurrency(defaultLevel = 4) { // If the "navigator.hardwareConcurrency" property // exists, we use that. Otherwise, we return the // "defaultLevel" value, which is a sane guess // at the actual hardware concurrency level. return Number.isInteger(navigator.hardwareConcurrency) ? navigator.hardwareConcurrency : defaultLevel; } console.log('concurrency level', getConcurrency()); // → concurrency level 8

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