or object state into a format that can be stored (e.g. files in secondary storage devices, data buffers in primary storage devices) or transmitted (e.g. data streams over computer networks) and reconstructed or object state into a format that can be stored (e.g. files in secondary storage devices, data buffers in primary storage devices) or transmitted (e.g. data streams over computer networks) and reconstructed XOffsetDatastructure, CppCon 2024 252.2 Current Solutions • The 2 Categories • MessagePack, Protocol Buffers, etc. • FlatBuffers, Cap’n Proto, etc. • Input, Output, and Process. // To better understand

back-end communicate with separate protocol Back-end implemented with Asio Queries serviced by proprietary database back-end (written in C++) 4 DataConn TCP protocol without login or encryption Intended using const_buffers_type = /* ... */; using mutable_buffers_type = /* ... */; std::size_t size() const; std::size_t max_size() const; std::size_t capacity() const; const_buffers_type data(std::size_t data(std::size_t pos, std::size_t n) const; mutable_buffers_type data(std::size_t pos, std::size_t n); void grow(std::size_t n); void shrink(std::size_t n); void consume(std::size_t n); }; 10 Limiting

being fast to be accurate • Latency constraint to not drop packets on the NIC ◦ Limited number of buffers ◦ Not reading fast enough will cause the application to drop packets, causing an outage • Up to TCPDirect - Custom TCP/UDP stack - Reduced set of features • EF_VI - Layer 2 API: interface, buffers and memory management (similar to DPDK) - Lowest latency onload --profile=latency ./algo_trader munmap, shm_unlink, ftruncate, flock... struct ProtocolHeader { std::arrayPROTOCOL_NAME_MAX_LENGTH> protocol_name; uint64_t magic_number; uint64_t buffer_size; uint32_t major_version; uint32_t

this” • But • Different transport mechanisms/libraries have different interfaces • Google protocol buffers, Flatbuffers, SBE, JSON, XML, and many, many more • The transport interface bleeds into the

2020 Major Features • Unified Shared Memory (USM) • Code with pointers can work naturally without buffers or accessors • Simplifies porting from most code (e.g. CUDA, C++) • Parallel Reductions • Added SYCL 2020 Hello WorldIn SYCL there are two memory management models; buffers and USM - here we will focus on buffers The buffers memory management model separates the storage and access of data and &e) { /* handle SYCL exception */ } } 29 SYCL 2020 Hello WorldIn the buffers memory management model there are buffers and accessors A buffer manage data across the host and one or more devices

thread does not already hold four buffers. 3. There are fewer than 16 other threads holding buffers, or this thread will wait until one of the others releases its buffers before acquiring one. 26• Stages

prepare_render_next_frame(); //get idle frame buffer and record command buffers for it submit_for_render(); //submit command buffers }Helmut Hlavacs – Combining Co-Routines and Functions into a Job System

“safer” solution? ▪ Accessors and buffers are distinct ▪ Simpler semantics that are easier to reason about ▪ But can lead to UB ▪ Accessors can sometimes keep buffers alive ▪ “Just works” in more circumstances

C++!) int a [[indeterminate]] ; Why didn’t C++ always do this? Cost, esp for large objects & buffers… In section 3, I’ll talk about how we can do even better…35 Q: Do you think it’s believable that

for C++: Motivation, Scope, and Basic Design ○ Wanted standard vocabulary types ■ Multichannel buffers: std::mdspan (?) ■ Frequency, sample time ● Searched for prior art ○ Found mp-units and… ○ P1935