Is Concurrent Writing to Separate Slice Elements in Go Safe?

Writing Concurrently to Slice Elements

In the given scenario, where multiple goroutines are attempting to modify different elements of a slice concurrently, the question arises whether this action is safe. While it may seem intuitive to assume that concurrent writes to separate slice elements should be permissible, it's essential to refer to the established principle of concurrent programming.

As specified in the Go language specification, if multiple goroutines concurrently access a variable, and at least one of those accesses involves a write, synchronization is mandatory. However, in the provided code snippet, the slice itself (the header) is not being written to. Instead, individual elements of the slice are being modified, which are akin to distinct variables.

Each slice element has its own memory space and is independent of the other elements. Therefore, the concurrent writes to different slice elements do not violate the aforementioned rule. Synchronization is still crucial, however, when reading from the results slice. The use of a waitgroup in this scenario ensures that the worker goroutines have completed their modifications before the results are accessed.

Consequently, the code snippet you provided is considered safe. You can confidently read the results from the 'results' slice after the Wait() function of the waitgroup returns, as this guarantees that all modifications have been completed and the results are complete.

In summary, while concurrent writes to individual slice elements are generally safe, it's imperative to synchronize access to the slice as a whole to ensure data integrity, particularly when reading from it.

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