On Tuesday, 2 January 2018 at 18:21:13 UTC, Tim Hsu wrote:
I am creating Vector3 structure. I use struct to avoid GC.
However, struct will be copied when passed as parameter to
function
struct Ray {
Vector3f origin;
Vector3f dir;
@nogc @system
this(Vector3f *origin, Vector3f *dir) {
this.origin = *origin;
this.dir = *dir;
}
}
How can I pass struct more efficiently?
This isn't a question for you. it's a question for the compiler,
let the compiler do its thing. Stick in a -O3 if you are using
GCC or LDC and build in release more not debug mode. Make sure
that the compiler can see the source code of the implementation
of the constructor wherever it is used and it should just be
inclined away to nonexistence. Your constructor should not even
exist, if it is then you are looking at a false picture or a
mistake where optimisation has been turned off for the sake of
easy source-level debugging.
Post up the assembler language output for a routine where this
code is used in some critical situation, and then we can help
make sure that the code _generation_ is optimal.
I reiterate, unless something is badly wrong or you are seeing a
red herring, no 'call' to the constructor code should even exist
in the cases where it is actually 'called'. You may well see a
useless copy of the constructor code because the compilers seem
to generate such even though it is never called ans so is a waste
of space. The compiler will analyse the constructor's
instructions and just copy-and-paste them as assignment
statements with that then getting thoroughly optimised down into
something which may just be a memory write or a register-register
copy that costs zero.
If you post up snippets of generated asm then U will be delighted
to take a look.
