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Why do smart pointers null out the wrapped pointer before destroying it?--Raymond Chen

By Adrien Hamelin | Jul 16, 2021 12:48 PM | Tags: community

Ever thought about it?

Why do smart pointers null out the wrapped pointer before destroying it?

by Raymond Chen

From the article:

When you null out a smart pointer type, the smart pointer type nulls out the old pointer before releasing it, rather than releasing the member and then setting it to null. Why does the old value get detached from the smart pointer before releasing it? Why not release it, and then set it to null?

CppCon 2020 2020: The Year of Sanitizers?--Victor Ciura

By Adrien Hamelin | Jul 16, 2021 12:44 PM | Tags: community

Registration is now open for CppCon 2021, which starts on October 24 and will be held both in person and online. To whet your appetite for this year’s conference, we’re posting videos of some of the top-rated talks from our most recent in-person conference in 2019 and our online conference in 2020. Here’s another CppCon talk video we hope you will enjoy – and why not register today for CppCon 2021 to attend in person, online, or both!

2020: The Year of Sanitizers?

by Victor Ciura

Summary of the talk:

Clang-tidy is the go-to assistant for most C++ programmers looking to improve their code, whether to modernize it or to find hidden bugs with its built-in checks. Static analysis is great, but you also get tons of false positives.

Now that you’re hooked on smart tools, you have to try dynamic/runtime analysis. After years of improvements and successes for Clang and GCC users, LLVM AddressSanitizer (ASan) is finally available on Windows, in the latest Visual Studio 2019 versions. Let's find out how this experience is for MSVC projects.

We’ll see how AddressSanitizer works behind the scenes (compiler and ASan runtime) and analyze the instrumentation impact, both in perf and memory footprint. We’ll examine a handful of examples diagnosed by ASan and see how easy it is to read memory snapshots in Visual Studio, to pinpoint the failure.

Want to unleash the memory vulnerability beast? Put your test units on steroids, by spinning fuzzing jobs with ASan in Azure, leveraging the power of the Cloud from the comfort of your Visual Studio IDE.

HPX V1.7.0 released -- STE||AR Group

By Hartmut Kaiser | Jul 14, 2021 12:28 PM | Tags: performance parallelism heterogeneous computing distributed computing concurrency c++20 c++17 c++14 c++11

The STE||AR Group has released V1.7.0 of HPX -- A C++ Standard library for parallelism and concurrency.

HPX V1.7.0 Released

The newest version of HPX (V1.7.0) is now available for download! This release continues the focus on C++20 conformance with multiple new algorithms adapted to be C++20 conformant and becoming customization point objects (CPOs). We’ve also added experimental support for using GCC’s SIMD data types with our parallel algorithms. Finally, we've implemented a large subset of sender/receiver functionality based on current proposals (mainly P0443, P1897, and P2300). HPX futures fulfill the sender concept, and senders can explicitly be turned into futures, which means that codebases can gradually adopt senders where appropriate. The full list of improvements, fixes, and breaking changes can be found in the release notes.

    HPX is a general purpose parallel C++ runtime system for applications of any scale. It implements all of the related facilities as defined by the C++ Standard. As of this writing, HPX provides one of the only widely available open-source implementation of the new C++17 parallel algorithms. Additionally, HPX implements functionalities proposed as part of the ongoing C++ standardization process, such as large parts of the features related parallelism and concurrency as specified by the upcoming C++20 Standard, the C++ Concurrency TS, Parallelism TS V2, data-parallel algorithms, executors, senders/receivers and many more. It also extends the existing C++ Standard APIs to the distributed case (e.g. compute clusters) and for heterogeneous systems (e.g. GPUs).

    HPX seamlessly enables a new Asynchronous C++ Standard Programming Model that tends to improve the parallel efficiency of our applications and helps reducing complexities usually associated with parallelism and concurrency.

 

C++20 three way comparison operator: Part 7--Gajendra Gulgulia

By Adrien Hamelin | Jul 14, 2021 11:14 AM | Tags: c++20

The series continue.

C++20 three way comparison operator: Part 7

by Gajendra Gulgulia

From the article:

In the fifth and sixth part of the tutorial series, I explained the comparison category std::strong_ordering and std::weak_ordering respectively with examples and use cases. In this part of the tutorial series, we take a closer look at the third and final comparison category, i.e. std::partial_ordering...

Classic Railroad Field Trip Announced--CppCon 2021

By Adrien Hamelin | Jul 14, 2021 11:11 AM | Tags: community

Will you participate?

Classic Railroad Field Trip Announced

From the article:

The CppCon 2021 Field Trip will be an adventure into the mountains to sample classic mountain cuisine from Beau Jo’s, followed by a train trip over the far-famed Georgetown Loop. Spend a fun-filled Sunday on October 24 with fellow attendees as we ascend to 9,101 ft (2,774 m) via air-conditioned buses and railroad coaches. This trip will encompass Geologic, Historic, Natural, and Culinary wonders west of Denver...

CppCon 2019 Abusing Your Memory Model for Fun and Profit--Samy Al Bahra, Paul Khuong

By Adrien Hamelin | Jul 14, 2021 11:06 AM | Tags: community

Registration is now open for CppCon 2021, which starts on October 24 and will be held both in person and online. To whet your appetite for this year’s conference, we’re posting videos of some of the top-rated talks from our most recent in-person conference in 2019 and our online conference in 2020. Here’s another CppCon talk video we hope you will enjoy – and why not register today for CppCon 2021 to attend in person, online, or both!

Abusing Your Memory Model for Fun and Profit

by Samy Al Bahra, Paul Khuong

Summary of the talk:

The most efficient concurrent C++ data structures used in the wild today usually achieve break-neck performance by either constraining their workload or constraining correctness to a particular memory model. The audience will learn about the Wild West of abusing memory models for performance and simplification, through real world examples. Non-blocking data structures and their benefits often come at the cost of increased latency because they require additional complexity in the common case. There are plenty of exceptions to this if the requirements of the data structure are relaxed, such as supporting only a bounded level of write or read concurrency or if correctness is constrained to a particular memory model. For this reason, well-designed specialized non-blocking data structures guarantee improved resiliency, throughput and latency in all cases compared to alternatives relying on traditional concurrency primitives. Specialized concurrent structures are common place in the Linux kernel and other performance critical systems.

You will learn about foundational concepts to understanding your underlying hardware's memory model and abusing memory models for fun and profit:
* Cache coherency
* Store Buffers
* Pipelines and speculative execution

This talk provides real-world examples that exploit the x86-TSO model to their advantage:
* A general technique to turn literally, any, open-addressed hash table into a concurrent hash table with low to negligible (near 0) cost. The transformation makes your hash table wait-free for writers and mostly wait-free for readers (lock-free in hypothetical worse cases) and is practical for languages such as C++. The mechanism is superior to the previously popular Azure lock-free hash table and even more importantly, practical for any non-garbage-collected environment. The overhead is negligible on TSO and low on non-TSO.
* Blazingly fast event counters. An extremely efficient replacement for condition variables is introduced and faster than any other alternative. This is implemented without requiring any heavy-weight atomic operations on the fast path by exploiting properties of the x86-TSO model.
* Scalable memory management: Exploit the ordering and visibility constraints of the underlying architecture for blazingly fast implementations of RCU and other safe memory reclamation schemes.
* and more.

Announcing the second set of AMAs for Meeting C++ 2021

By Meeting C++ | Jul 14, 2021 01:51 AM | Tags: meetingcpp event conference community c++17

Today I can share with you the second set of AMAs at Meeting C++ 2021

Announcing the second set of AMAs for Meeting C++ 2021

by Jens Weller

From the article:

This second set of C++ Experts nicely completes the first one. Its now a mix of folks involved with the C++ Standard complimented with experience in C++ and other languages. All of them have made contributions to C++ and our community, very much looking forward to see the set of questions for each of them in November!

CppCon 2020 A Parallel and Heterogeneous Task Programming System Using Modern C++--Tsung-Wei Huang

By Adrien Hamelin | Jul 12, 2021 12:39 PM | Tags: community

Registration is now open for CppCon 2021, which starts on October 24 and will be held both in person and online. To whet your appetite for this year’s conference, we’re posting videos of some of the top-rated talks from our most recent in-person conference in 2019 and our online conference in 2020. Here’s another CppCon talk video we hope you will enjoy – and why not register today for CppCon 2021 to attend in person, online, or both!

A Parallel and Heterogeneous Task Programming System Using Modern C++

by Tsung-Wei Huang

Summary of the talk:

The Taskflow project addresses the long-standing question: "How can we make it easier for developers to write parallel and heterogeneous programs with high performance and simultaneous high productivity?" Modern scientific computing relies on a heterogeneous mix of computational patterns, domain algorithms, and specialized hardware to achieve key scientific milestones that go beyond traditional capabilities. However, programming these applications often requires complex expert-level tools and a deep understanding of software methodologies. Specifically, the lack of a suitable software environment that can overcome the complexity of programming large parallel and heterogeneous systems has posed a significant barrier for many organizations to facilitate transformational discoveries.

Taskflow develops a simple and powerful task programming model to enable efficient implementations of heterogeneous decomposition strategies. Our programming model empowers users with both static and dynamic task graph constructions to incorporate a broad range of computational patterns including hybrid CPU-GPU computing, dynamic control flow, and irregularity. We develop an efficient heterogeneous work-stealing strategy that adapts worker threads to available task parallelism at any time during the graph execution. We have demonstrated promising performance of Taskflow on both micro-benchmark and real-world applications. As an example, we solved a large machine learning workload by up to 1.5× faster, 1.6× less memory, and 1.7× fewer lines of code than two industrial-strength systems, oneTBB and StarPU, on a machine of 40 CPUs and 4 GPUs.

This talk will cover three aspects: (1) heterogeneous task programming model using modern C++, (2) an efficient work-stealing strategy generalizable to arbitrary heterogeneous domains, and (3) user experience we have obtained and suggested roadmap for C++ in face of future heterogeneity.

The Taskflow project is available at https://taskflow.github.io/

C++20 three way comparison operator--Gajendra Gulgulia

By Adrien Hamelin | Jul 12, 2021 12:37 PM | Tags: c++20

The series continue.

C++20 three way comparison operator part 5 and part 6

by Gajendra Gulgulia

From the article:

In the fourth part of the tutorial, I introduced the theoretical ideas behind the return types of the three way operator in C++20 and demonstrated that there might be semantic restrictions on the program that allow for comparison of equivalence instead of equality. Also I demonstrated by a simple example when can two objects be semantically incomparable, even though the syntax of program allows to compare them and how to deal with such cases with the help of operator<=>...