Which is faster in Go: `append()` or slice assignment?

Performance Comparison of Slice Append and Assignment in Go

In Go, slicing plays a significant role in managing data efficiently. However, questions arise regarding the performance differences between two commonly used slice operations: append and assignment.

Append vs. Assign

The append() operation extends the existing slice with additional elements, while the assignment operator (=), when applied to slices, simply overwrites the existing elements with new values.

Performance Analysis

Benchmarking the following code demonstrates the performance gap:

Benchmark results indicate that "a[i] = i" (assignment) consistently outperforms "a = append(a, i)" (append):

Explanation

The faster performance of "a[i] = i" can be attributed to its direct assignment nature. It simply assigns the value i to the corresponding element in the slice.

In contrast, "a = append(a, i)" involves a series of operations:

1. Copy the existing slice header.
2. Create a temporary slice for variadic parameters (i).
3. Reslice a if there's sufficient capacity (provided in the benchmark).
4. Assign i to the last element of a.
5. Update the slice header in a local variable (a).

These extra steps introduce overhead compared to the direct assignment in "a[i] = i".

Conclusion

Understanding the performance differences between slice operations is crucial for optimizing code efficiency. For simple value assignment, "a[i] = i" proves to be a more efficient choice. However, when expanding the slice is necessary, "a = append(a, i)" remains the appropriate approach.

The above is the detailed content of Which is faster in Go: `append()` or slice assignment?. For more information, please follow other related articles on the PHP Chinese website!