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ZEN TIMER CPU SOFTWARE
ZEN TIMER CPU CODE

processorĪnother problem that I like is bitset decoding. I find that AMD is about 10% to 15% behind Intel. The Skylake processor has the highest frequency. This is an instruction-heavy benchmark: the numbers of mispredicted branches and cache misses are small. The two stages together effectively parse a JSON document. I record the number of instructions per cycle, as measured by CPU counters, in the two stages of processing. I use GNU GCC 8 under Linux, I process a test file called twitter.json using the benchmark command line parse.

ZEN TIMER CPU SOFTWARE

Let us consider a piece of software that has a high number of instructions per cycle, the fast JSON parser simdjson. I have only had access to a recent AMD processors (Zen 2) for a short time, but in this short time, I have routinely found that it has a lower number of instructions per cycle than even older Intel processors. Thus “work per unit of time normalized per CPU frequency” and “instructions per cycle” are distinct notions. In theory, a processor limited to one instruction per cycle could beat a modern Intel processor on many tasks if they had powerful instructions and faster data access. Rather it appears that they are measures of the amount of work done per unit of time normalized by processor frequency.

However, it is not clear whether these reports are genuinely based on measures of instruction per cycle. It has been reported that the most recent AMD processors surpass Intel in terms of instructions per cycle. One smaller company that is making Intel nervous is AMD. However, Intel is increasingly being challenged. Up until recently, Intel produced the best commodity processors: its processors had the highest frequencies, the most instructions per cycle, the most powerful instructions and so forth. Thus a 3.4GHz processor has 3.4 billion cycles per second, but it might easily execute 7 billion instructions per second on a single core. Modern processors can execute many instructions per cycle. Physics makes it difficult to produce processors that have higher frequency. For example, processors with a higher frequency tend to do more work per unit of time. The performance of a processor is determined by several factors.

Tarun Elankath on Cost of a thread in C++ under Linux.

Piotr Grochowski on Number Parsing at a Gigabyte per Second.

Daniel Lemire on Cost of a thread in C++ under Linux.

Daniel Lemire on I do not use a debugger.

David on Performance tip: constructing many non-trivial objects is slow.

Faster bitset decoding using Intel AVX-512.

ZEN TIMER CPU CODE

Avoid exception throwing in performance-sensitive code.

Data structure size and cache-line accesses.Memory-level parallelism : Intel Ice Lake versus Amazon Graviton 3.

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