Agner's CPU blog

My microarchitecture manual explains the branch prediction in different microprocessors.

The "likely" macro is a hint to the compiler, not to the CPU. The compiler may swap if-else branches to put the most likely branch first.

No, you need root permission. Installing the linux driver requires sudo.

Vladislav_152378 wrote: What is predication they're all talking about? It is the use of masks. A mask can selectively enable or disable individual vector elements. Mysticial wrote: If 512-bit was split into the different pipes on the same cycle, it should be 1.0/cycle as you wouldn't be able to use ...

I have now had access to test a Zen 4, and the results are quite good. The Zen 4 is produced with a 5 nm process making it possible to run at a clock frequency of 4.5 - 5.7 GHz. The high clock frequency combined with a bigger micro-op cache, L2, and L3 caches, improved branch instructions, and sever...

nanxiao wrote:

it is said the Rust program performance is quite good

The Rust compiler is based on LLVM, the same as Clang is using. This means that you can get similar performance as Clang C++ in some cases, but not all. You better do your own tests.

Dannotech wrote: it would only split AVX 512 into half and double pump it through the AVX 256 vector engine to save power This was expected. It saves silicon space. It might still give a performance benefit in the decoding stage. I will test the performance if somebody can give me remote access to a...

C++ is the best programming language if you want programs to run fast. My C++ optimization manual explains why. The number of C++ compilers on the market is decreasing. Many compilers have disappeared from the market or are no longer maintained. Do you remember compiler names like Borland, Embarcade...

There is an important update to this story. Intel have switched to a Clang-based compiler that works well with non-Intel microprocessors. If you download the new Intel "oneAPI" Compiler, you get two versions. A legacy version named "Classic" which is a continuation of the old compiler, and a new "LL...

Version 2.02.00 of the Vector Class Library is now released. Link . New in this version: Half precision floating point vectors, using the new AVX512-FP16 instruction set (or emulated on lower instruction sets). Includes all general functions and operators, exponential function, trigonometric functio...