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标题: How to determine the number of CPUs and amount of RAM should I use in Gaussian ? [打印本页]

作者
Author: Julien 时间: 2022-4-9 03:00
标题: How to determine the number of CPUs and amount of RAM should I use in Gaussian ?
Hi,
Recently, I started to run my first calculations using Gaussian on a workstation : Nb of core : 6, 12 threads, and 64 GB in memory.

Should I use blindly all the the 6 core and the full amount of memory every time i run a calculation in purpose to speed it up, or there is some rules to assign the number of CPUs and amount of memory necessary to fastly terminate a job.
I read in some web page : "The following formula can be used to estimate the memory requirement of various types of Gaussian jobs (in 8-byte words): M + 2(NB)^2, where NB is the number of basis functions used in the calculation, and M is a minimum value that is usually generously covered by the default memory size."

作者
Author: sobereva 时间: 2022-4-9 11:20
If you are using 32 bit Gaussian, you can at most use four CPU cores. If you are using 64bit Gaussian, you should set %nprocs=6 (number of CPU physical cores) to maximally use CPU resources.

If there is no other applications that take up a lot of memory, it is suggested to set %mem=55GB to maximally and safely use spare physical memory.

作者
Author: Julien 时间: 2022-4-9 14:38

sobereva 发表于 2022-4-9 11:20
If you are using 32 bit Gaussian, you can at most use four CPU cores. If you are using 64bit Gaussia ...

Thank you very much for the clarifications.
I just want to understand two more things:
1-is it possible to use the number of logical cores (in my case : 12 logical core) ?
2-which keyword we use in Gaussian, %NProcShared, or %NProc ?

作者
Author: abin 时间: 2022-4-9 17:52
Either %nproc or %nprocshared does the job.
For gaussian 16, use %cpu instead.
Check the manual for details.

作者
Author: Julien 时间: 2022-4-10 13:38

abin 发表于 2022-4-9 17:52
Either %nproc or %nprocshared does the job.
For gaussian 16, use %cpu instead.
Check the manual f ...

Thank you very much abin,
Is it possible to use the number of logical cores (in my case : 12 logical core) ?

作者
Author: abin 时间: 2022-4-10 14:00

Julien 发表于 2022-4-10 13:38
Thank you very much abin,
Is it possible to use the number of logical cores (in my case : 12 logi ...

g09, negative.
g16, %CPU=0-11/2.

Or, you can disable hyper threads.

作者
Author: snljty 时间: 2022-4-11 18:29

abin 发表于 2022-4-10 14:00
g09, negative.
g16, %CPU=0-11/2.

按照卢老师的测试结果http://sobereva.com/392，这个不是物理核心间隔着使用，每个被用的物理核心两个逻辑核心都占满嘛？

作者
Author: abin 时间: 2022-4-11 18:48
本帖最后由 abin 于 2022-4-11 18:53 编辑

snljty 发表于 2022-4-11 18:29
按照卢老师的测试结果http://sobereva.com/392，这个不是物理核心间隔着使用，每个被用的物理核心两个逻 ...

高斯手册有提及，
仅限于机器所有资源你独占，仅用一半核心最佳。

如果还有别的事情在做，而且有没有资源绑定，当然慢的一塌糊涂了。

我所有的前提都是假定，干活的机器就是干活的，
干活的机器就只用来干活，不会跑什么浏览器呀，文档呀之类的。
而且也是资源独占型的。

当然，对于一边跑计算，还一边跑浏览器，看文献，
是不适用的。

你看我提供的公开的工作站初始配置脚本，
都是默认关闭图形界面的，
都是建议slurm+cgroup 限定的。
另外，在CPU密集型的生产环境，
超线程带来的性能提升有限。
而超线程导致用户的脚本数错资源，
可能造成性能下降，
或者计算等待等，
负面作用一堆……

性能提升有限，麻烦还不止一个的时候，当然是关闭了最佳……

要不，你去租用超算，
开超线程，标价为六分钱，
你喜不喜欢？

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