Do Go's Type Assertions and Type Switches Introduce Significant Performance Overhead?

Type Assertions and Type Switches in Go: Performance Implications

Type assertions and type switches are mechanisms in Go used for introspecting and working with dynamic types at runtime. While these features offer flexibility, concerns may arise regarding their performance overhead.

One might question whether type assertions and type switches in Go exhibit poor performance or introduce significant latency, particularly compared to other type checking approaches. This article delves into this question by analyzing benchmark results and providing a comparative analysis.

Benchmark Results

To assess the performance impact of type assertions and type switches, a benchmark test was conducted. The benchmark measures the time taken to invoke a method on an interface value using different approaches:

• Direct method invocation through the interface
• Type switch to access the method
• Type assertion to cast and access the method

AMD R7 2700X Machine (Golang v1.12.9)

• Direct method invocation: 1.67 ns/op
• Interface: 2.03 ns/op
• Type switch: 1.70 ns/op
• Type assertion: 1.67 ns/op

amd64 Machine (January 2015)

• Direct method invocation: 2.71 ns/op
• Interface: 2.98 ns/op
• Type switch: 16.7 ns/op
• Type assertion: 13.8 ns/op

Based on these results, it is evident that type switch and type assertion incur a negligible performance penalty compared to direct method invocation and interface calls on both AMD R7 2700X and amd64 machines.

Performance Relative to C

The provided benchmark does not include a comparison with C or C. In theory, C 's reliance on casting and runtime type information (RTTI) could potentially result in slower performance. However, this is determined by the implementation and optimizations employed by the specific C compiler.

Conclusion

The benchmark results demonstrate that in Go, type assertions and type switches perform efficiently and do not introduce a substantial performance overhead. For most practical scenarios, the choice between these techniques can be based primarily on code readability and design considerations rather than performance concerns.

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