hellerbarde

Latency numbers every programmer should know

L1 cache reference ......................... 0.5 ns
Branch mispredict ............................ 5 ns
L2 cache reference ........................... 7 ns
Mutex lock/unlock ........................... 25 ns
Main memory reference ...................... 100 ns             
Compress 1K bytes with Zippy ............. 3,000 ns  =   3 µs
Send 2K bytes over 1 Gbps network ....... 20,000 ns  =  20 µs
SSD random read ........................ 150,000 ns  = 150 µs

Read 1 MB sequentially from memory ..... 250,000 ns = 250 µs

bkaradzic

Orthodox C++

What is Orthodox C++?

Orthodox C++ (sometimes referred as C+) is minimal subset of C++ that improves C, but avoids all unnecessary things from so called Modern C++. It's exactly opposite of what Modern C++ suppose to be.

Why not Modern C++?

NSExceptional

Build settings reference

Active Build Action (ACTION)

A string identifying the build system action being performed.

Additional SDKs (ADDITIONAL_SDKS)

The locations of any sparse SDKs that should be layered on top of the one specified by Base SDK (SDKROOT). If more than one SDK is listed, the first one has highest precedence. Every SDK specified in this setting should be a "sparse" SDK, for example, not an SDK for an entire macOS release.

Alternate Install Group (ALTERNATE_GROUP)

tkersey

Build settings reference

Active Build Action (ACTION)

A string identifying the build system action being performed.

Additional SDKs (ADDITIONAL_SDKS)

The locations of any sparse SDKs that should be layered on top of the one specified by Base SDK (SDKROOT). If more than one SDK is listed, the first one has highest precedence. Every SDK specified in this setting should be a "sparse" SDK, for example, not an SDK for an entire macOS release.

Alternate Install Group (ALTERNATE_GROUP)

tclementdev

libdispatch efficiency tips

The libdispatch is one of the most misused API due to the way it was presented to us when it was introduced and for many years after that, and due to the confusing documentation and API. This page is a compilation of important things to know if you're going to use this library. Many references are available at the end of this document pointing to comments from Apple's very own libdispatch maintainer (Pierre Habouzit).

My take-aways are:

• You should create very few, long-lived, well-defined queues. These queues should be seen as execution contexts in your program (gui, background work, ...) that benefit from executing in parallel. An important thing to note is that if these queues are all active at once, you will get as many threads running. In most apps, you probably do not need to create more than 3 or 4 queues.

• Go serial first, and as you find performance bottle necks, measure why, and if concurrency helps, apply with care, always validating under system pressure. Reuse

dsabanin

defaults write com.apple.dt.Xcode ShowDVTDebugMenu -bool YES
sudo mkdir -p /Applications/Xcode.app/Contents/Developer/AppleInternal/Library/Xcode
sudo touch /Applications/Xcode.app/Contents/Developer/AppleInternal/Library/Xcode/AppleInternal.plist

# Don't forget to restart Xcode

stuartcarnie

   Copyright 2020 Stuart Carnie

   Licensed under the Apache License, Version 2.0 (the "License");
   you may not use this file except in compliance with the License.
   You may obtain a copy of the License at

     http://www.apache.org/licenses/LICENSE-2.0

   Unless required by applicable law or agreed to in writing, software
   distributed under the License is distributed on an "AS IS" BASIS,