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A comment on Porting a Ray Tracer to Rust, Part 1.

Re:Porting a Ray Tracer to Rust, Part 1 by CyberDildonics on Wednesday December 31, 2014 @06:39AM (#8818990)
So one important question about Rust that is relevant here is how it handles dynamic stack allocation. It is in the language? C++ has alloca of course but needs a couple of macros to work across compilers. Memory allocation ends up being a very big performance concern in renderers. PBRT uses both memory arenas and an ALLOCA macro.
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Re:Porting a Ray Tracer to Rust, Part 1 by berkut on Wednesday December 31, 2014 @07:02AM (#8819038)
It's quite possible to not use alloca(), but just use C++'s placement new operator to re-use memory already allocated on the stack.

I'm not sure if Rust has something similar to placement new, but I'm sure custom allocators (for memory arenas) are possible in Rust.

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Re:Porting a Ray Tracer to Rust, Part 1 by steveklabnik on Wednesday December 31, 2014 @08:24AM (#8819241)
User-defined placement new and custom allocators for existing data structures are still being worked on. `box` can do a form of placement new already, and while you can use your own allocator, you can't use it with already-existing types.
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Re:Porting a Ray Tracer to Rust, Part 1 by CyberDildonics on Wednesday December 31, 2014 @08:16AM (#8819210)
That is a valid and useful technique, but being able to dynamically allocate stack memory in the first place is separate from using placement new on stack memory.
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Re:Porting a Ray Tracer to Rust, Part 1 by berkut on Wednesday December 31, 2014 @08:19AM (#8819226)
Of course, I was just pointing out it's not always necessary to use alloca - I've written a production-level path-tracer without needing to allocate stack memory dynamically.
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Re:Porting a Ray Tracer to Rust, Part 1 by yuriks on Wednesday December 31, 2014 @07:24AM (#8819082)
I might be mistaken about this, but I believe they plan on implementing support for this at some point.
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Re:Porting a Ray Tracer to Rust, Part 1 by steveklabnik on Wednesday December 31, 2014 @08:28AM (#8819260)
It's on the todo list.
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