• =?UTF-8?B?Tm9yZGzDtnc=?= (10/10) Mar 04 2018 When zeroing a slice of memory (either stack or heap) such as
• bauss (3/13) Mar 04 2018 This is worth reading:
• kinke (10/20) Mar 05 2018 I'd recommend not concerning yourself with such low-level

=?UTF-8?B?Tm9yZGzDtnc=?= <per.nordlow gmail.com> writes:

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?

bauss <jj_1337 live.dk> writes:

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

kinke <noone nowhere.com> writes:

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).