On 03/03/2011 19:34, Jeremy Maitin-Shepard wrote:
On 03/03/2011 05:46 AM, Mathias Gaunard wrote:
[snip] Imagine something similar to the mpn component of the GMP library, but with a generic and easy-to-use C++ interface. Through genericity, you could make the algorithms accept ranges of integers and have them work regardless of digit size, with the digit chosen at the discretion of the user. If the user provides a SIMD type as a digit, you'll get optimized SIMD code for free, for example, in a completely externalized way. Now *that* would be awesome.
This whole explicitly passing simd<T> in place of T, which seems to be the same thing done in nt2, in order to make use of certain optimizations seems like a poor interface choice.
I'm talking of passing a range of 128-bit or 256-bit integers, with an integer type that would use the SIMD unit for its implementation, instead of a range of 32-bit or 64-bit integers that would use the standard built-in types that probably use the ALU. Of course, this is just an idea. I don't know if that is a sensible way to exploit SIMD in a bigint scenario, maybe you need a more global SIMD awareness.
I also don't see how the optimization can be externalized in the (quite common) case of doing more than element-wise operations.
A C primitive only receives a pointer to raw memory, and has to decide what code to invoke itself. Templates allow to externalize those operations to functions that depend on the types of its arguments. --------------- Also, in nt2, simd_<T> is a notation to do pattern matching on simd vector types whose elements are T. It's not something you "pass" to functions. You could also write simd_< integer_<T> > to only match simd vector types whose elements are integers. NT2 uses a hierarchical concept-based overloading system. I understand this can make code quite confusing in the absence of any docs.