Question

I have a problem with the SLMATH library. Not sure if anyone uses it or has used it before? Anyway, the issue is that when I compile with SSE optimisation enabled (in VS 2010), I obviously have to provide a container that has the correct byte alignment for SSE type objects. This is OK because there’s a little class in SLMATH that’s an aligned vector; it aligns the vector allocation on an 8 byte boundary (i.e. I do not use std::vector<>).

Now the problem is that it appears any structure or class that contains something like slm::mat4 must also be aligned on such a boundary too, before it’s put into a collection. So, for example, I used an aligned vector to create an array of slm::mat4, but if I create a class called Mesh, and Mesh contains an slm::mat4 and I want to put Mesh into a std::vector, well, I get strange memory errors whilst debugging.

So given the documentation is very sparse indeed, can anyone who’s used this library tell me what, precisely, I have to do to use it with SSE optimisation? I mean I don’t like the idea of having to use aligned vectors absolutely everywhere in place of std::vector just in case an slm:: component ends up being encapsulated into a class or structure somehow.

Alternatively, a fast vector/matrix/graphics math library as good as SLMATH would be great if there’s on around.

Thanks for any advice you can offer.

Edit 1: Simple repro-case not using SLMATH illustrates the problem:

#include <vector>

class Item
{

public:

    __declspec(align(8))
    struct {

        float a, b, c, d;

    } Aligned;
};


int main()
{
    // Error - won't compile.

    std::vector<Item> myItems;
}

Robin

Answer 1

It might work if you when you declare your variable to use __declspec(align) on your variable declarations, or to wrap them within a struct that declares itself to be aligned properly. I have not used the library in question, but it seems that this might be the issue you are facing.

The reference for the align option can be found here.