When zeroing a slice of memory (either stack or heap) such as

    enum n = 100;
    ubyte[n] chunk;

should I use `memset` such as

    memset(chunk.ptr, 0, n/2); // zero first half

or an array assignment such as

    chunk[0 .. n/2] = 0; // zero first half

or are they equivalent in release mode?

Further, does it depend on whether the slice length is known at compile-time or not?

On Sunday, 4 March 2018 at 15:23:41 UTC, Nordlöw wrote:
> When zeroing a slice of memory (either stack or heap) such as
>
>     enum n = 100;
>     ubyte[n] chunk;
>
> should I use `memset` such as
>
>     memset(chunk.ptr, 0, n/2); // zero first half
>
> or an array assignment such as
>
>     chunk[0 .. n/2] = 0; // zero first half
>
> or are they equivalent in release mode?
>
> Further, does it depend on whether the slice length is known at compile-time or not?

This is worth reading:

https://stackoverflow.com/questions/3654905/faster-way-to-zero-memory-than-with-memset

On Sunday, 4 March 2018 at 15:23:41 UTC, Nordlöw wrote:
> When zeroing a slice of memory (either stack or heap) such as
>
>     enum n = 100;
>     ubyte[n] chunk;
>
> should I use `memset` such as
>
>     memset(chunk.ptr, 0, n/2); // zero first half
>
> or an array assignment such as
>
>     chunk[0 .. n/2] = 0; // zero first half
>
> or are they equivalent in release mode?
>
> Further, does it depend on whether the slice length is known at compile-time or not?

I'd recommend not concerning yourself with such low-level optimizations and let the compiler do that for you, and only jump in yourself if profiling/benchmarking shows that there's a bottleneck, and prefer nice readable code otherwise.
E.g., LDC will lower `chunk[0 .. n/2] = 0` to a memset() call if the length is unknown at compile-time, and otherwise replace it with good-looking assembly code (xor vector register and store it consecutively to memory): https://run.dlang.io/is/I6Fq9G (click on ASM and check the assembly for the two functions).