Go Goroutines: Parallelism or Serialization? When Will `go` Statements Actually Run in Parallel?

Go Statement Execution: Parallelism or Serialization?

When executing a Go code, developers might encounter situations where a "go" statement doesn't result in parallel execution despite multiple cores available. Let's explore this issue and identify possible causes and solutions.

In the provided code, the developer attempts to perform parallel summation using goroutines. However, it's observed that only one core is being utilized. To enable parallel execution, it's crucial to understand the Go programming model and its limitations.

The Go FAQ provides valuable insights into concurrency and parallelism in Go. Two specific questions shed light on this issue:

1. Multiple CPUs Utilization:

The statement "You must set the GOMAXPROCS shell environment variable or use the similarly-named function of the runtime package to allow the run-time support to utilize more than one OS thread" explains the need to explicitly configure the number of OS threads to be used by the Go runtime. By default, Go limits the number of threads to the number of cores available on the system. To increase the number of parallel goroutines, the developer should set GOMAXPROCS accordingly.

2. Context Switching Penalty:

The other question highlights the issue of context switching when using multiple OS threads. In scenarios where goroutines communicate frequently through channels, sending data between threads incurs a significant context-switching penalty. This can lead to performance degradation rather than improvement. Therefore, it's important to assess the nature of the application and the communication pattern between goroutines when configuring GOMAXPROCS.

By reviewing the Go FAQ and addressing these factors, developers can optimize their code for effective parallel execution. It's crucial to set GOMAXPROCS appropriately and consider potential performance implications related to context switching when using multiple cores.

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