如何计算flops

电玩女神 2022-01-23 00:05 549阅读 0赞

这里FLOPs (FLoating-point Operations Per Second)是衡量浮点性能的常用单位，即每秒做的浮点运算次数。它常被用来估算电脑的执行效能，尤其是在使用到大量浮点运算的[科学计算][Link 1]领域中。

*  cpu个数计算

CPUs = **(Threads per core)** x **(cores per socket) **x **(sockets**)

即cpu数目与节点数、核数和单核的线程数有关。详见关于节点数和核数的[定义][Link 2]。linux系统中这三个指标可通过如下命令查询。

lscpu | grep -E '^Thread|^Core|^Socket|^CPU\('
    
    CPU(s):                40
    Thread(s) per core:    2
    Core(s) per socket:    10
    Socket(s):             2

*  flops计算

performance in GFlops = (CPU speed in GHz) x (CPU instruction per cycle) x (number of CPU cores) x  (number of CPUs per node)

*  multithread vs hyperthread

多线程是在一个cpu核上运行的软件处理技术，需要cpu完成线程之间的调度工作。超线程是在一个cpu核上虚拟出多个cpu核的硬件处理技术，每个虚拟核都是独立的运行单元(processor)，查看processor的命令为 ‘cat /proc/cpuinfo’。

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2h6aGoyMDA3_size_16_color_FFFFFF_t_70][] 图片来自 [这里][Link 3]

参考文献：

1.  [http://www.novatte.com/our-blog/197-how-to-calculate-peak-theoretical-performance-of-a-cpu-based-hpc-system][http_www.novatte.com_our-blog_197-how-to-calculate-peak-theoretical-performance-of-a-cpu-based-hpc-system]
2.  [basic definition: node, socket, core][Link 2]
3.  [CPU Basics: Multiple CPUs, Cores, and Hyper-Threading Explained][CPU Basics_ Multiple CPUs_ Cores_ and Hyper-Threading Explained]
4.  [How to know number of cores of a system in Linux?][How to know number of cores of a system in Linux]
5.  [How to calculate peak theoretical performance of a CPU-based HPC system？][http_www.novatte.com_our-blog_197-how-to-calculate-peak-theoretical-performance-of-a-cpu-based-hpc-system]
6.  [计算能力][Link 4]
7.  [What Are Threads in a Processor?][What Are Threads in a Processor]
8.  What is hyper-threading? How does it different from multithreading?

[Link 1]: http://baike.baidu.com/edit/FLOPS/989494?dl=2#
[Link 2]: https://scicomp.stackexchange.com/questions/7530/difference-between-nodes-and-cpus-when-running-software-on-a-cluster
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2h6aGoyMDA3_size_16_color_FFFFFF_t_70]: /images/20220123/5163b393a1684816b718c94037737eb5.png
[Link 3]: https://www.google.nl/url?sa=i&source=imgres&cd=&cad=rja&uact=8&ved=2ahUKEwjih5Ov2cfiAhVmEqYKHciTD50QjRx6BAgBEAU&url=https%3A%2F%2Fwww.techpowerup.com%2F234667%2Fcritical-flaw-in-hyperthreading-discovered-in-skylake-and-kaby-lake-cpus%3Fcp%3D4&psig=AOvVaw2YfsB3iTZ4gdKV5DAQtKTc&ust=1559458317397252
[http_www.novatte.com_our-blog_197-how-to-calculate-peak-theoretical-performance-of-a-cpu-based-hpc-system]: http://www.novatte.com/our-blog/197-how-to-calculate-peak-theoretical-performance-of-a-cpu-based-hpc-system
[CPU Basics_ Multiple CPUs_ Cores_ and Hyper-Threading Explained]: https://www.howtogeek.com/194756/cpu-basics-multiple-cpus-cores-and-hyper-threading-explained/
[How to know number of cores of a system in Linux]: https://unix.stackexchange.com/questions/218074/how-to-know-number-of-cores-of-a-system-in-linux
[Link 4]: https://blog.csdn.net/hit_shaoqi/article/details/75452200
[What Are Threads in a Processor]: https://whatsabyte.com/blog/processor-threads/