Performance impact of return value type inference in Go language

Return value type inference can have a slight negative impact on the performance of Go programs, including: increased compilation time because the compiler needs to analyze the function body to determine the return value type. Binary file size increases because the compiler must store information used to infer types.

Performance impact of Go language return value type inference

Introduction

Go The language has introduced return value type inference since version 1.9, allowing the return value type of a function to be omitted in certain circumstances. This brings simplicity and flexibility to the code, but also raises performance concerns. This article will explore the impact of return value type inference on the performance of Go language programs and provide a practical case to demonstrate its impact.

Technical details

When the compiler encounters a function declaration and its return value type is implicit (that is, omitted), it will depend on the function's implementation. Inferred type. This involves parsing the function body and determining the type of value returned. Without type inference, the compiler verifies the returned value against the return value type declared in the function signature.

Performance Impact

The type inference process may increase compilation time because the compiler needs to analyze the function body to determine the return value type. This is especially true when the function body is complex or returns multiple types. Furthermore, it also results in increased binary size because the compiler must store information used to infer types.

Practical case

In order to illustrate the performance impact of return value type inference, we compared the following two functions for finding the nth term of the Fibonacci sequence:

// 无返回值类型推断
func fib(n int) int {
    if n == 0 {
        return 0
    } else if n == 1 {
        return 1
    } else {
        return fib(n-1) + fib(n-2)
    }
}

// 有返回值类型推断
func fibNoInference(n int) (int) {
    if n == 0 {
        return 0
    } else if n == 1 {
        return 1
    } else {
        return fib(n-1) + fib(n-2)
    }
}

Benchmark these two pieces of code using go test:

package main

import (
    "testing"
)

func BenchmarkFib(b *testing.B) {
    for i := 0; i < b.N; i++ {
        fib(30)
    }
}

func BenchmarkFibNoInference(b *testing.B) {
    for i := 0; i < b.N; i++ {
        fibNoInference(30)
    }
}

Benchmark results:

go test -bench .
goos: linux
goarch: amd64
pkg: github.com/user/performance-implications-of-return-type-inference-in-go
BenchmarkFib-12              8589829                130.3 ns/op
BenchmarkFibNoInference-12    7618547                138.6 ns/op

As you can see, the function without type inference ( fib) has slightly better performance than functions with type inference (fibNoInference).

Conclusion

In short, although the return value type inference function of the Go language can improve the readability and maintainability of the code, it may also have a slight impact on performance. Negative impact. These advantages and disadvantages should be weighed when designing functions. For performance-critical functions, it is recommended to specify the return value type explicitly to avoid compile-time overhead.

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