#cpp26 — Public Fediverse posts

ACCU on Sea 2026 SESSION ANNOUNCEMENT: Portable Reflection in C++26 by Dan Katz

https://accuonsea.uk/2026/sessions/portable-reflection-in-cpp26

Register now at https://accuonsea.uk/tickets/

#cpp26 #reflection #programming #coding

@glloyd It crops up in other places, not just iterators. I first encountered it using a coroutine library where the promise type was a std::expected. I did the usual “how am I being stupid” for a while before I figured it wasn’t me (for once). #cpp #cplusplus #clang #cpp26

@bjn that is a great bug.
simplified https://godbolt.org/z/MnEGcE595

#cpp #cplusplus #programming #clang #cpp26

Two more results. This time without using std::simd. One uses a plain loop over C[i, j] += A[i, k] * B[k, j] (in the inner kernel—it is still blocked over all levels of the cache hierarchy).

This is ~10–30x slower.

1/2

#stdsimd #cpp26 #simd

Two more results. This time without using std::simd. One uses a plain loop over C[i, j] += A[i, k] * B[k, j] (in the inner kernel—it is still blocked over all levels of the cache hierarchy).

This is ~10–30x slower.

1/2

#stdsimd #cpp26 #simd

Two more results. This time without using std::simd. One uses a plain loop over C[i, j] += A[i, k] * B[k, j] (in the inner kernel—it is still blocked over all levels of the cache hierarchy).

This is ~10–30x slower.

1/2

#stdsimd #cpp26 #simd

ACCU on Sea 2026 SESSION ANNOUNCEMENT: Demystifying C++ initializer_list - Design, Behavior, and Best Practices by Prithvi Okade & Chandranath Bhattacharyya

https://accuonsea.uk/2026/sessions/demystifying-cpp-initializer_list-design-behavior-and-best-practices/

Register now at https://accuonsea.uk/tickets/

#constexpr #Cpp26 #Cpp #Programming

mdspan rocks! A simple switch to go from layout_right to layout_right_padded and performance for larger matrices goes 📈 up! (e.g. 4096×4096 from 76GFLOP/s to 100GFLOP/s) I introduced padding of one cache line between rows to avoid cache associativity virtually reducing cache sizes.
For small matrices the extra padding is counterproductive, though. But mdspan abstracts it all away. The matrix-mul function is unchanged.

#stdsimd #mdspan #cpp26 #optimization

I've been looking into matrix multiplication using std::simd and std::mdspan/submdspan (all single-threaded).
I got to 86% of peak FLOP. x86_64 AVX2 has 32/16 FLOP/cycle peak (2 FMAs per cycle).
I suspect better performance needs a more cache-friendly layout mapping. This is using layout_right.

#stdsimd #simd #mdspan #cpp26 #cpp

I've been looking into matrix multiplication using std::simd and std::mdspan/submdspan (all single-threaded).
I got to 86% of peak FLOP. x86_64 AVX2 has 32/16 FLOP/cycle peak (2 FMAs per cycle).
I suspect better performance needs a more cache-friendly layout mapping. This is using layout_right.

#stdsimd #simd #mdspan #cpp26 #cpp

I've been looking into matrix multiplication using std::simd and std::mdspan/submdspan (all single-threaded).
I got to 86% of peak FLOP. x86_64 AVX2 has 32/16 FLOP/cycle peak (2 FMAs per cycle).
I suspect better performance needs a more cache-friendly layout mapping. This is using layout_right.

#stdsimd #simd #mdspan #cpp26 #cpp

I've been looking into matrix multiplication using std::simd and std::mdspan/submdspan (all single-threaded).
I got to 86% of peak FLOP. x86_64 AVX2 has 32/16 FLOP/cycle peak (2 FMAs per cycle).
I suspect better performance needs a more cache-friendly layout mapping. This is using layout_right.

#stdsimd #simd #mdspan #cpp26 #cpp

I've been looking into matrix multiplication using std::simd and std::mdspan/submdspan (all single-threaded).
I got to 86% of peak FLOP. x86_64 AVX2 has 32/16 FLOP/cycle peak (2 FMAs per cycle).
I suspect better performance needs a more cache-friendly layout mapping. This is using layout_right.

#stdsimd #simd #mdspan #cpp26 #cpp

C++26: A User-Friednly assert() macro

https://www.sandordargo.com/blog/2026/03/25/cpp26-user-friendly-assert

#HackerNews #C++26 #UserFriendly #assert #Macro #Cpp26 #HackerNews #Programming

C++26: A User-Friednly assert() macro

https://www.sandordargo.com/blog/2026/03/25/cpp26-user-friendly-assert

#HackerNews #C++26 #UserFriendly #assert #Macro #Cpp26 #HackerNews #Programming

C++26: A User-Friednly assert() macro

https://www.sandordargo.com/blog/2026/03/25/cpp26-user-friendly-assert

#HackerNews #C++26 #UserFriendly #assert #Macro #Cpp26 #HackerNews #Programming

C++26: A User-Friednly assert() macro

https://www.sandordargo.com/blog/2026/03/25/cpp26-user-friendly-assert

#HackerNews #C++26 #UserFriendly #assert #Macro #Cpp26 #HackerNews #Programming

C++26: A User-Friednly assert() macro

https://www.sandordargo.com/blog/2026/03/25/cpp26-user-friendly-assert

#HackerNews #C++26 #UserFriendly #assert #Macro #Cpp26 #HackerNews #Programming

The first part of std::simd just landed in #GCC 16: https://forge.sourceware.org/gcc/gcc-mirror/commit/8be0893fd98c9a89bbcd81e0ff8ebae60841d062
Expect it on Compiler Explorer in — I guess — 12 hours.

#simd #wg21 #cpp #cpp26 #cplusplus

The first part of std::simd just landed in #GCC 16: https://forge.sourceware.org/gcc/gcc-mirror/commit/8be0893fd98c9a89bbcd81e0ff8ebae60841d062
Expect it on Compiler Explorer in — I guess — 12 hours.

#simd #wg21 #cpp #cpp26 #cplusplus

The first part of std::simd just landed in #GCC 16: https://forge.sourceware.org/gcc/gcc-mirror/commit/8be0893fd98c9a89bbcd81e0ff8ebae60841d062
Expect it on Compiler Explorer in — I guess — 12 hours.

#simd #wg21 #cpp #cpp26 #cplusplus

The first part of std::simd just landed in #GCC 16: https://forge.sourceware.org/gcc/gcc-mirror/commit/8be0893fd98c9a89bbcd81e0ff8ebae60841d062
Expect it on Compiler Explorer in — I guess — 12 hours.

#simd #wg21 #cpp #cpp26 #cplusplus

The first part of std::simd just landed in #GCC 16: https://forge.sourceware.org/gcc/gcc-mirror/commit/8be0893fd98c9a89bbcd81e0ff8ebae60841d062
Expect it on Compiler Explorer in — I guess — 12 hours.

#simd #wg21 #cpp #cpp26 #cplusplus

CLion 2025.3 Is Here, and It’s Epic: Faster Language Engine, Unique Constexpr Debugger, DAP Support, and Much More
#Clang #CLion #News #Releases #Clionnova #Constexpr #Cpp26 #Dap #Stm32 #Zephyrwest

https://blog.jetbrains.com/clion/2025/12/2025-3-release/

constexpr all the things! Since the evaluation of a constant expression never results in an erroneous behavior (EB, C++26)! (But use constexpr since C++11)

This was mentioned by many at the conference, not to forget: @DanielaKEngert, Mikhail Svetkin, and others.

@meetingcpp #cpp #cpp26 #cpp11 #meetingcpp #dev #undefined_behavior #ub #erroneous_behavior #eb

constexpr all the things! Since the evaluation of a constant expression never results in an erroneous behavior (EB, C++26)! (But use constexpr since C++11)

This was mentioned by many at the conference, not to forget: @DanielaKEngert, Mikhail Svetkin, and others.

@meetingcpp #cpp #cpp26 #cpp11 #meetingcpp #dev #undefined_behavior #ub #erroneous_behavior #eb

constexpr all the things! Since the evaluation of a constant expression never results in an erroneous behavior (EB, C++26)! (But use constexpr since C++11)

This was mentioned by many at the conference, not to forget: @DanielaKEngert, Mikhail Svetkin, and others.

@meetingcpp #cpp #cpp26 #cpp11 #meetingcpp #dev #undefined_behavior #ub #erroneous_behavior #eb

constexpr all the things! Since the evaluation of a constant expression never results in an erroneous behavior (EB, C++26)! (But use constexpr since C++11)

This was mentioned by many at the conference, not to forget: @DanielaKEngert, Mikhail Svetkin, and others.

@meetingcpp #cpp #cpp26 #cpp11 #meetingcpp #dev #undefined_behavior #ub #erroneous_behavior #eb

constexpr all the things! Since the evaluation of a constant expression never results in an erroneous behavior (EB, C++26)! (But use constexpr since C++11)

This was mentioned by many at the conference, not to forget: @DanielaKEngert, Mikhail Svetkin, and others.

@meetingcpp #cpp #cpp26 #cpp11 #meetingcpp #dev #undefined_behavior #ub #erroneous_behavior #eb

Run-time reflexion in C++26... Wow, i was expecting that since 2004. That's one of the reasons we meta-programmed Dynamic Types in CLAM.

#cpp #clam #cpp26

https://www.youtube.com/watch?v=TOKP7k66VBw