This idea of **asynchronous** code described above is also sometimes called **"concurrency"**. It is different from **"parallelism"**.

**Concurrency** and **parallelism** both relate to "different things happening more or less at the same time".

But the details between *concurrency* and *parallelism* are quite different.

To see the difference, imagine the following story about burgers:

- shutdown: вимкнення
- lifespan: тривалість життя
- authorization: авторизація
- forwarded header: направлений заголовок
- dependable: залежний
- dependent: залежний
- bound: межа
- concurrency: рівночасність
- parallelism: паралелізм
- multiprocessing: багатопроцесорність
- env var: змінна оточення
- dict: словник
- enum: перелік
- issue: проблема
- server worker: серверний працівник
- worker: працівник

# 並行與 async / await { #concurrency-and-async-await }

有關*路徑操作函式*的 `async def` 語法的細節與非同步 (asynchronous) 程式碼、並行 (concurrency) 與平行 (parallelism) 的一些背景知識。

## 趕時間嗎? { #in-a-hurry }

<abbr title="too long; didn't read - 太長不看"><strong>TL;DR:</strong></abbr>

如果你正在使用要求你以 `await` 語法呼叫的第三方函式庫，例如：

```Python
results = await some_library()
```

然後，使用 `async def` 宣告你的*路徑操作函式*：


```Python hl_lines="2"
@app.get('/')

					updates <- cache.clone()
					return
				}
				cache.replace(v.Name, v.Parent, v.Entry)
				cache.Info.LastUpdate = time.Now()
			}
		}
	}()

	// Restrict parallelism for disk usage scanner
	// upto GOMAXPROCS if GOMAXPROCS is < len(disks)
	maxProcs := runtime.GOMAXPROCS(0)
	if maxProcs < len(disks) {
		disks = disks[:maxProcs]
	}

	// Start one scanner per disk

### 동시성이 병렬성보다 더 나은가요? { #is-concurrency-better-than-parallelism }

아니요! 그게 이 이야기의 교훈은 아닙니다.

동시성은 병렬성과 다릅니다. 그리고 많은 기다림이 포함되는 **특정한** 시나리오에서는 더 낫습니다. 그 때문에 웹 애플리케이션 개발에서는 일반적으로 병렬성보다 훨씬 더 낫습니다. 하지만 모든 것에 해당하진 않습니다.

그래서 균형을 맞추기 위해, 다음의 짧은 이야기를 상상해보세요:

   *
   * <p>To avoid having this type, we could use {@code FlatMapSpliterator} directly. The main
   * advantages to having the type are the ability to use its constructor reference below and the
   * parallelism with the primitive version. In short, it makes its caller ({@code flatMap})
   * simpler.
   *
   * @param <InElementT> the element type of the input spliterator

   *
   * <p>To avoid having this type, we could use {@code FlatMapSpliterator} directly. The main
   * advantages to having the type are the ability to use its constructor reference below and the
   * parallelism with the primitive version. In short, it makes its caller ({@code flatMap})
   * simpler.
   *
   * @param <InElementT> the element type of the input spliterator

* the `Authorization` header
* the forwarded header

* the dependency injection system
* the dependency
* the dependable
* the dependant

* I/O bound
* CPU bound
* concurrency
* parallelism
* multiprocessing

* the env var
* the environment variable
* the `PATH`
* the `PATH` variable

* the authentication
* the authentication provider
* the authorization

你可以同时拥有并行性和异步性，你可以获得比大多数经过测试的 NodeJS 框架更高的性能，并且与 Go 不相上下， Go 是一种更接近于 C 的编译语言（[全部归功于 Starlette](https://www.techempower.com/benchmarks/#section=data-r17&hw=ph&test=query&l=zijmkf-1)）。

### 并发比并行好吗？ { #is-concurrency-better-than-parallelism }

不！这不是故事的本意。

并发不同于并行。而是在需要大量等待的特定场景下效果更好。因此，在 Web 应用程序开发中，它通常比并行要好得多，但这并不意味着全部。

因此，为了平衡这一点，想象一下下面的短篇故事：

> 你必须打扫一个又大又脏的房子。

*是的，这就是完整的故事。*

---

    /**
     * ProjectBuilder parallelism.
     *
     * @since 4.0.0
     */
    @Config(type = "java.lang.Integer", defaultValue = "cores/2 + 1")
    public static final String MAVEN_MODEL_BUILDER_PARALLELISM = "maven.modelBuilder.parallelism";

    /**
     * User property for enabling/disabling the consumer POM feature.
     *