| #include <stdint.h> | |
| typedef unsigned char U8; | |
| typedef unsigned short U16; | |
| typedef unsigned int U32; | |
| typedef unsigned long long U64; | |
| typedef intptr_t SINTa; | |
| struct KernelState | |
| { |
| We agreed beforehand that we don't care about tininess-before-or-after-rounding shenanigans. :) | |
| With that out of the way, the idea is to do something like this: | |
| fma(af, bf, cf): | |
| # All arithmetic done with RN | |
| ad = float_to_double(af) | |
| bd = float_to_double(bf) | |
| cd = float_to_double(cf) | |
This is a short post that explains how to write a high-performance matrix multiplication program on modern processors. In this tutorial I will use a single core of the Skylake-client CPU with AVX2, but the principles in this post also apply to other processors with different instruction sets (such as AVX512).
Matrix multiplication is a mathematical operation that defines the product of
What is strict aliasing? First we will describe what is aliasing and then we can learn what being strict about it means.
In C and C++ aliasing has to do with what expression types we are allowed to access stored values through. In both C and C++ the standard specifies which expression types are allowed to alias which types. The compiler and optimizer are allowed to assume we follow the aliasing rules strictly, hence the term strict aliasing rule. If we attempt to access a value using a type not allowed it is classified as undefined behavior(UB). Once we have undefined behavior all bets are off, the results of our program are no longer reliable.
Unfortunately with strict aliasing violations, we will often obtain the results we expect, leaving the possibility the a future version of a compiler with a new optimization will break code we th
| $ wget http://people.centos.org/tru/devtools-2/devtools-2.repo -O /etc/yum.repos.d/devtools-2.repo | |
| $ yum install devtoolset-2-gcc devtoolset-2-binutils | |
| $ yum install devtoolset-2-gcc-c++ devtoolset-2-gcc-gfortran | |
