The Generic SIMD Library allowers users to write C++ SIMD codes that are portable across different SIMD ISAs.
//HelloSIMD.cpp
#include <iostream>
#include <gsimd.h>
int main (int argc, char* argv[])
{
svec<4,float> v1(1.1, 2.2, 3.3, 4.4);
svec<4,float> v2 = v1 * 2;
std::cout << "Hello World: " << v2 << std::endl;
return 0;
}Let's use the example above to illustrate some of the basics features of the library:
The library provides:
Fixed-lane SIMD vectors. Our SIMD vectors are defined based on the number of elements per vector (fixed-lane) instead of the byte-length of a vector (fixed-width). This is the key diffence between our vector types and the ones defined in platform-specific intrinsics.
We choose fixed-lane vector because it is more natural to SIMDized parallel loops that involve data of different length such as int and double.
We intend to support vectors with arbitrary power-of-two lanes, but currently only 4-element vectors are supported. Vector of 2-, and 8-elements are under development.
Portable SIMD programming. The programming interface of the library is completely platform neutral. The library provides mapping from the interface to target SIMD platforms. The current release supports the following target platforms:
Overloaded C++ semantics on SIMD vectors. We define SIMD vector operations based on semantics of C++ operators instead of platform-specific ISA semantics. This is because the semantics of C++ operators are platform independent. Secondly, C++ operators provide a slightly higher semantics than platform-specific intrinsics and are more natural to program since most users understand C++ operators well.