travisdowns

The counters that are the easiest to understand and the best for making ratios that are internally consistent (i.e., always fall in the range 0.0 to 1.0) are the mem_load_retired events, e.g., mem_load_retired.l1_hit and mem_load_retired.l1_miss.

These count at the instruction level, i.e., the universe of retired instructions. For example, could make a reasonable hit ratio from mem_load_retired.l1_hit / mem_inst_retired.all_loads and it will be sane (never indicate a hit rate more than 100%, for example).

That one isn't perfect though, in that it may not reflect the true costs of cache misses and the behavior of the program for at least the following reasons:

• It appplies only to loads and can't catch misses imposed by stores (AFAICT there is no event that counts store misses).
• It only counts loads that retire - a lot of the load activity in your process may be due to loads on a speculative path that never retire. Loads on a speculative path may bring in data that is never used, causing misses and d

brycelelbach

template <typename InputIt, typename OutputIt>
OutputIt
radix_sort_split(InputIt first, InputIt last, OutputIt output, std::uint64_t bit)
{
  std::vector<std::uint64_t> e(std::distance(first, last));

  // Count 0s.
  std::transform(first, last, e.begin(),
                 [=] (auto t) { return !(t & (1 << bit)); });

brycelelbach

template <typename InputIt, typename OutputIt, typename BinaryOp, typename T, typename Size>
unique_future<OutputIt>
async_inclusive_scan(InputIt first, InputIt last, OutputIt output,BinaryOp op, T init, Size chunk_size)
{
  Size const elements = std::distance(first, last);
  Size const chunks   = (1 + ((elements - 1) / chunk_size)); // Round up.

  std::vector<unique_future<T>> sweep;
  sweep.reserve(chunks);

pervognsen

I was told by @mmozeiko that Address Sanitizer (ASAN) works on Windows now. I'd tried it a few years ago with no luck, so this was exciting news to hear.

It was a pretty smooth experience, but with a few gotchas I wanted to document.

First, download and run the LLVM installer for Windows: https://llvm.org/builds/

Then download and install the VS extension if you're a Visual Studio 2017 user like I am.

It's now very easy to use Clang to build your existing MSVC projects since there's a cl compatible frontend:

beached

C++ Operator Signatures

This is a list of C++ operators that can be overloaded and their normal signatures(a.k.a what an int would do). The order is the preffered order to use them(The first one listed is often preffered)

Arithmetic

operator+ addition

• free function -> T operator+( T const & lhs, T const & rhs )
• member function -> T operator+( T const & rhs ) const

operator+ unary plus

• member function -> T operator+( ) const

Leandros

/* Copyright (c) 2018 Arvid Gerstmann. */
/* This code is licensed under MIT license. */
#ifndef AG_RANDOM_H
#define AG_RANDOM_H

class splitmix
{
public:
    using result_type = uint32_t;
    static constexpr result_type (min)() { return 0; }

krzysztof-jusiak

//
// Copyright (c) 2018 Kris Jusiak (kris at jusiak dot net)
//
// Distributed under the Boost Software License, Version 1.0.
// (See accompanying file LICENSE_1_0.txt or copy at
// http://www.boost.org/LICENSE_1_0.txt)
//
#pragma once
#if not defined(__cpp_variadic_templates) or                                   \
    not defined(__cpp_rvalue_references) or not defined(__cpp_decltype) or     \

mojobojo

// Clearly the best hello world out there.
#define _ATL_ATTRIBUTES 1
#define _WINDLL 1
#include <atlbase.h>
#include <atlcom.h>
#include <string.h>
#include <comdef.h>
#include <string>
#include <fstream>
#include <iostream>

shafik

What is the Strict Aliasing Rule and Why do we care?

(OR Type Punning, Undefined Behavior and Alignment, Oh My!)

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

hfiref0x

//
// Ref = src
// https://www.blackhat.com/docs/eu-17/materials/eu-17-Liberman-Lost-In-Transaction-Process-Doppelganging.pdf
//
// Credits:
//  Vyacheslav Rusakov @swwwolf
//  Tom Bonner @thomas_bonner
//

#include <Windows.h>