[petsc-users] Parallelization efficiency diagnose

[Sun, Hui]

Thank you Jed. I don't know how to use "lstopo" from the hwloc, but I looked up the cores and memory from the hardware overview from my MAC, it has

Number of Processors:	1
Total Number of Cores:	2

Besides, as you said, there are 4 logical cores due to hyperthreading. However, I'm still expecting to get speed doubled because I have 2 real cores. So where is the restriction then? 

Best,
Hui


________________________________________
From: Jed Brown [jed at jedbrown.org]
Sent: Thursday, December 04, 2014 5:02 PM
To: Sun, Hui; petsc-users at mcs.anl.gov
Subject: Re: [petsc-users] Parallelization efficiency diagnose

"Sun, Hui" <hus003 at ucsd.edu> writes:

> Estimation of possible speedup of MPI programs based on Streams benchmark.
>
> It appears you have 1 node(s)
>
>
> Does this result basically says that my MacBook only have one node?
> However, I know my computer has 4 cores, as I type sysctl -n hw.ncpu
> in bash, it gives me 4. What does it really mean? By the way, here is
> my configuration for this installation:

Use "lstopo" from the hwloc package to see how your cores are laid out.
You probably have two physical cores, each with hypethreading (4 logical
cores), sharing the same memory bus.  One thread saturates the memory
bus, so you get no speedup by using more cores.

http://www.mcs.anl.gov/petsc/documentation/faq.html#computers