Re: st: Stata/MP licenses for the number of threads or cores on modern CPUs?

[Sergiy Radyakin <serjradyakin@gmail.com>]

László,

to answer your question: "Does it mean it is rarely worth paying for
double the number of threads?"
we need to know your utility function. For some people a speed-up of
one percent might be worth thousands of $$, yet for others even
doubling the speed would be left unnoticed.

In any case Stata is not the only program running on your computer.
Even if it is the main workhorse for the user, there are usually some
50 processes running in Windows simultaneously, which eat up some of
the resources. So providing extra execution threads to them frees up a
steady pool of threads for Stata. Things become less straightforward
when you find sharing a server with someone crunching numbers in Maple
or Matlab, or running SQL queries, or CFD simulations.

HyperThreading is not a magic solution to double the performance of
your CPU. While presenting twice more virtual cores to your OS, the
performance increase might be <30% level (see
http://en.wikipedia.org/wiki/Hyper-threading). The optimization comes
not from the commands executing faster, but because of reducing the
overheads of the commands, most importantly fetching, and decoding
commands, loading command arguments from memory, and saving the
results. So while your CPU's ALU is busy adding two numbers for one
thread, the memory can be queried for the operation code for another
thread. It will not get executed right away though.

16-core AMD Opterons (based on 32nm Abu Dhabi cores) are currently
available from NewEgg and other vendors in the US for less than $1,000
USD; but at 115W they consume more power than all of the lights in my
living room combined :)
Anyhow, the full system including memory can probably be built for the
current price of the Stata MP4. A ready made HP Proliant Server with
2xOpteron 6376 is available at NewEgg for $4,534 USD (plus shipping
:). That will give you a crazy 32 core machine, though with only 32GB
of memory in the base configuration. It is expandable to 768GB, which
gives you plenty of playroom for upgrades in the future.

Higher number of cores does not necessarily translate into higher
overall performance, as this chart from AMD confirms:
http://www.amd.com/PublishingImages/Public/Graphic_ChartsDiagrams/BenchmarkJPEG/Opteron6300/2P_INT_Perf_Price.jpg
but it definitely increases the licensing costs.

Hope this helps.

Best, Sergiy Radyakin




On Sat, Aug 3, 2013 at 2:55 PM, László Sándor <sandorl@gmail.com> wrote:
> Hi,
>
> The Stata/MP hardware advisory says "Be aware of the term
> “hyperthreaded”, however. Stata/MP runs faster on hyperthreaded
> processors, but not as fast as it would if you had full cores instead
> of hyperthreads. Computers with multiple hyperthreaded processors are
> suitable for Stata/MP. The number of real processors is the critical
> factor."
> http://www.stata.com/products/compatible-operating-systems-mp/
>
> Does it mean it is rarely worth paying for double the number of
> threads? Esp. as one does need to buy twice as many Stata/MP licenses
> then? Or Stata/MP licenses do apply by the number of physical cores
> anyway?
>
> E.g. see the list of modern server CPUs from Intel:
> http://ark.intel.com/compare/75052,75461,75054,75055,75462,75056,75464,75057,75466,75465
> with fancier chips offering double the number of cores for threads.
> (Explanation: "Intel® Hyper-Threading Technology (Intel® HT
> Technology) delivers two processing threads per physical core. Highly
> threaded applications can get more work done in parallel, completing
> tasks sooner.")
>
> Probably our money is better spent on large and fast RAM, then?
>
> (Though I am also surprised these chips apparently limited to 1600 MHz
> dual-channel DDR3 RAM.)
>
> Thanks a lot for any thoughts on this matter,
>
> Laszlo
>
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