For credit purposes, the standard is peak FLOPS,
i.e. we give credit for what the device could do,
rather than what it actually did.
Among other things, this encourages projects to develop more efficient apps.
Currently we're not measuring this well for x86 CPUs,
since our Whetstone benchmark isn't optimized.
Ideally the BOINC client should include variants for the most common
CPU features, as we do for ARM.
-- D
On 10-Jun-2014 2:09 AM, Richard Haselgrove wrote:
Before anybody leaps into making any changes on the basis of that observation, I
think we ought to pause and consider why we have a benchmark, and what we use
it for.
I'd suggest that in an ideal world, we would be measuring the actual running
speed
of (each project's) science applications on that particular host, optimisations
and
all. We gradually do this through the runtime averages anyway, but it's hard to
gather a priori data on a new host.
Instead of (initially) measuring science application performance, we measure
hardware performance as a surrogate. We now have (at least) three ways of doing
that:
x86: minimum, most conservative, estimate, no optimisations allowed for.
Android: allows for optimised hardware pathways with vfp or neon, but doesn't
relate
back to science app capability.
GPU: maximum theoretical 'peak flops', calculated from card parameters, then
scaled
back by rule of thumb.
Maybe we should standardise on just one standard?
------------------------------------------------------------------------------------
*From:* Richard Haselgrove <[email protected]>
*To:* Josef W. Segur <[email protected]>; David Anderson
<[email protected]>
*Cc:* "[email protected]" <[email protected]>
*Sent:* Tuesday, 10 June 2014, 9:37
*Subject:* Re: [boinc_dev] EXIT_TIME_LIMIT_EXCEEDED (sorry, yes me again,
but
please read)
http://boinc.berkeley.edu/gitweb/?p=boinc-v2.git;a=commit;h=7b2ca9e787a204f2a57f390bc7249bb7f9997fea
>________________________________
> From: Josef W. Segur <[email protected] <mailto:[email protected]>>
>To: David Anderson <[email protected]
<mailto:[email protected]>>
>Cc: "[email protected] <mailto:[email protected]>"
<[email protected] <mailto:[email protected]>>; Eric J
Korpela
<[email protected] <mailto:[email protected]>>; Richard
Haselgrove
<[email protected] <mailto:[email protected]>>
>Sent: Tuesday, 10 June 2014, 2:19
>Subject: Re: [boinc_dev] EXIT_TIME_LIMIT_EXCEEDED (sorry, yes me again,
but
please read)
>
>
>Consider Richard's observation:
>
>>> It appears that the Android Whetstone benchmark used in the BOINC
client has
>>> separate code paths for ARM, vfp, and NEON processors: a vfp or
NEON
processor
>>> will report that it is significantly faster than a plain-vanilla
ARM.
>
>If that is so, it distinctly differs from the x86 Whetstone which never
uses
SIMD, and is truly conservative as you would want for 3).
>--
> Joe
>
>
>
>On Mon, 09 Jun 2014 16:43:17 -0400, David Anderson <[email protected]
<mailto:[email protected]>> wrote:
>
>> Eric:
>>
>> Yes, I suspect that's what's going on.
>> Currently the logic for estimating job runtime
>> (estimate_flops() in sched_version.cpp) is
>> 1) if this (host, app version) has > 10 results, use (host, app version)
statistics
>> 2) if this app version has > 100 results, use app version statistics
>> 3) else use a conservative estimate based on p_fpops.
>>
>> I'm not sure we should be doing 2) at all,
>> since as you point out the first x100 or 1000 results for an app version
>> will generally be from the fastest devices
>> (and even in the steady state,
>> app version statistics disproportionately reflect fast devices).
>>
>> I'll make this change.
>>
>> -- David
>>
>> On 09-Jun-2014 8:10 AM, Eric J Korpela wrote:
>>> I also don't have direct access to the server as well, so I'm mostly
guessing.
>>> Having separate benchmarks for neon and VFP means there's a broad
bimodal
>>> distribution for the benchmark results. Where the mean falls depends
upon
the mix
>>> of machines. In general the neon machines (being newer and faster)
will report
>>> first and more often, so early on the PFC distribution will reflect
the fast
>>> machines. Slower machines will be underweighted. So the work will be
estimated to
>>> complete quickly, and some machines will time out. In SETI beta, it
resolves itself
>>> in a few weeks. I can't guarantee that it will anywhere else.
>>>
>>> We see this with every release of a GPU app. The real capabilities of
graphics
>>> cards vary by orders of magnitude from the estimate and by more from
each
other.
>>> The fast cards report first and most every else hits days of timeouts.
>>>
>>> One possible fix so to increase the timeout limits for the first 10
workunits for a
>>> host_app_version, until host based estimates take over.
>>>
>>>
>>>
>>>
>>> On Mon, Jun 9, 2014 at 2:02 AM, Richard Haselgrove
<[email protected] <mailto:[email protected]>
>>> <mailto:[email protected]
<mailto:[email protected]>>> wrote:
>>>
>>> I think Eric Korpela would be the best person to answer that
question,
but I
>>> suspect 'probably not': further investigation over the weekend
suggests
that the
>>> circumstances may be SIMAP-specific.
>>>
>>> It appears that the Android Whetstone benchmark used in the BOINC
client has
>>> separate code paths for ARM, vfp, and NEON processors: a vfp or
NEON
processor
>>> will report that it is significantly faster than a plain-vanilla
ARM.
>>>
>>> However, SIMAP have only deployed a single Android app, which I'm
assuming only
>>> uses ARM functions: devices with vfp or NEON SIMD vectorisation
available would
>>> run the non-optimised application much slower than BOINC expects.
>>>
>>> At my suggestion, Thomas Rattei (SIMAP admistrator) increased the
>>> rsc_fpops_bound multiplier to 10x on Sunday afternoon. I note that
the
maximum
>>> runtime displayed on
http://boincsimap.org/boincsimap/server_status.php has
>>> already increased from 11 hours to 14 hours since he did that.
>>>
>>> Thomas has told me "We've seen that [EXIT_TIME_LIMIT_EXCEEDED] a
lot.
However,
>>> due to Samsung PowerSleep, we thought these are mainly "lazy" users
just not
>>> using their phone regularly for computing." He's going to monitor
how this
>>> progresses during the remainder of the current batch, and I've
asked
him to keep
>>> us updated on his observations.
>>>
>>>
>>>
>>> >________________________________
>>> > From: David Anderson <[email protected]
<mailto:[email protected]> <mailto:[email protected]
<mailto:[email protected]>>>
>>> >To: [email protected]
<mailto:[email protected]>
<mailto:[email protected] <mailto:[email protected]>>
>>> >Sent: Monday, 9 June 2014, 3:48
>>> >Subject: Re: [boinc_dev] EXIT_TIME_LIMIT_EXCEEDED (sorry, yes me
again, but
>>> please read)
>>> >
>>> >
>>> >Does this problem occur on SETI@home?
>>> >-- David
>>> >
>>> >On 07-Jun-2014 2:51 AM, Richard Haselgrove wrote:
>>> >
>>> >> 2) Android runtime estimates
>>> >>
>>> >> The example here is from SIMAP. During a recent pause between
batches, I noticed
>>> >> that some of my 'pending validation' tasks were being slow to
clear:
>>> >> http://boincsimap.org/boincsimap/results.php?hostid=349248
>>> >>
>>> >> The clearest example is the third of those three workunits:
>>> >> http://boincsimap.org/boincsimap/workunit.php?wuid=57169928
>>> >>
>>> >> Four of the seven replications have failed with 'Error while
computing', and
>>> >> every one of those four is an EXIT_TIME_LIMIT_EXCEEDED on an
Android device.
>>> >>
>>> >> Three of the four hosts have never returned a valid result
(total
credit zero),
>>> >> so they have never had a chance to establish an APR for use in
runtime
>>> >> estimation: runtime estimates and bounds must have been
generated
by the server.
>>> >>
>>> >> It seems - from these results, and others I've found pending on
other machines -
>>> >> that SIMAP tasks on Android are aborted with
EXIT_TIME_LIMIT_EXCEEDED after ~6
>>> >> hours elapsed. For the new batch released today, SIMAP are
using a
3x bound
>>> >> (which may be a bit low under the circumstances):
>>> >>
>>> >> <rsc_fpops_est>13500000000000.000000</rsc_fpops_est>
>>> >> <rsc_fpops_bound>40500000000000.000000</rsc_fpops_bound>
>>> >>
>>> >> so I deduce that the tasks when first issued had a runtime
estimate
of ~2 hours.
>>> >>
>>> >> My own tasks, on a fast Intel i5 'Haswell' CPU (APR 7.34
GFLOPS),
take over half
>>> >> an hour to complete: two hours for an ARM device sounds
suspiciously low. The
>>> >> only one of my Android wingmates to have registered an APR
>>> >>
(http://boincsimap.org/boincsimap/host_app_versions.php?hostid=771033) is
>>> showing
>>> >> 1.69 GFLOPS, but I have no way of knowing whether that APR was
established
>>> before
>>> >> or after the task in question errored out.
>>> >>
>>> >> From experience - borne out by current tests at Albert@Home,
where
server logs
>>> >> are helpfully exposed to the public - initial server estimates
can
be hopelessly
>>> >> over-optimistic. These two are for the same machine:
>>> >>
>>> >> 2014-06-04 20:28:09.8459 [PID=26529] [version] [AV#716]
(BRP4G-cuda32-nv301)
>>> >> adjusting projected flops based on PFC avg: 2124.60G 2014-06-07
09:30:56.1506
>>> >> [PID=10808] [version] [AV#716] (BRP4G-cuda32-nv301) setting
projected flops
>>> based
>>> >> on host elapsed time avg: 23.71G
>>> >>
>>> >> Since SIMAP have recently announced that they are leaving the
BOINC
platform at
>>> >> the end of the year (despite being an Android launch partner
with
Samsung), I
>>> >> doubt they'll want to put much effort into researching this
issue.
>>> >>
>>> >> But if other projects experimenting with Android applications
are
experiencing a
>>> >> high task failure rate, they might like to check whether
>>> EXIT_TIME_LIMIT_EXCEEDED
>>> >> is a significant factor in those failures, and if so, consider
the
other
>>> >> remediation approaches (apart from outliers, which isn't
relevant
in this case)
>>> >> that I suggested to Eric Mcintosh at LHC.
>
>
>
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