Nebula: Completing the SETI@home pipeline

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Profile Chris SCrowdfunding Project Donor*Special Project $75 donor
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Message 1830284 - Posted: 13 Nov 2016, 12:14:44 UTC

Rest assured, if possible, the kitties shall be involved in the next generation of this most important scientific project.

Yes me too Mark. Seti MkII with GBT data is almost upon us.

and to me it seems that nebula will finally conclude and finnish S@H. Which is past due....

Yes well, that is pretty typical of what we would expect from you. The rest of us will carry on with the search, bye bye. S&H as a scientific project is not finished, just the first phase of it is being evaluated, before we move on to Phase II.
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Message 1830430 - Posted: 13 Nov 2016, 23:19:57 UTC

Thanks for detailed description.

So far one place rises questions:
Autocorrelation: a repeating pattern of unknown shape and period, manifested by a correlation between the data and a shifted copy of itself. Autocorrelation uses the time-domain data; FFT is not used.


In fact autocorr applied after dechirping on 128k FFT only (so both back and forth transforms are done before autocorr starts)
So what "FFT not used could mean"?
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Message 1830654 - Posted: 15 Nov 2016, 2:52:32 UTC - in response to Message 1829052.  
Last modified: 15 Nov 2016, 3:40:10 UTC

From this page:
http://setiathome.berkeley.edu/nebula_web/persistent.php

"We use a resolution at which each pixel is about as large as a telescope beam.
This resolution divides the sphere into 2^26 (about 54 million) pixels, of which about 16 million are visible from the Arecibo telescope."

From code:
https://setisvn.ssl.berkeley.edu/trac/browser/seti_science/nebula/tables.h

// largest possible pixel#
//
#define MAX_PIXEL (2<<26)


I think 2<<26 == 2^27

e.g. 2<<1 == 4 == 2^2

http://www.c4learn.com/c-programming/c-bitwise-left-shift-operator/


Note: In the above I used "^" to denote "power", not XOR
 



- ALF - "Find out what you don't do well ..... then don't do it!" :)
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Message 1830708 - Posted: 15 Nov 2016, 11:42:56 UTC - in response to Message 1830654.  
Last modified: 15 Nov 2016, 11:43:39 UTC

From this page:
http://setiathome.berkeley.edu/nebula_web/persistent.php

"We use a resolution at which each pixel is about as large as a telescope beam.
This resolution divides the sphere into 2^26 (about 54 million) pixels, of which about 16 million are visible from the Arecibo telescope."

From code:
https://setisvn.ssl.berkeley.edu/trac/browser/seti_science/nebula/tables.h

// largest possible pixel#
//
#define MAX_PIXEL (2<<26)


I think 2<<26 == 2^27

e.g. 2<<1 == 4 == 2^2

http://www.c4learn.com/c-programming/c-bitwise-left-shift-operator/


Note: In the above I used "^" to denote "power", not XOR
 

Hee hee, good catch...

Should not that "#define MAX_PIXEL (2<<26)" actually be:

#define MAX_PIXEL (1<<26)

?

That is, "1" left-shifted 26 places to give 2^26 ?


FLOSS in action :-)

Keep searchin',
Martin
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Take a look for yourself: Linux Format
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Message 1830724 - Posted: 15 Nov 2016, 13:21:54 UTC - in response to Message 1830654.  

This resolution divides the sphere into 2^26 (about 54 million) pixels...

The other (cosmetic) typo is that 2^26 == 67108864 which is not really "about 54 million"



- ALF - "Find out what you don't do well ..... then don't do it!" :)
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Message 1830757 - Posted: 16 Nov 2016, 2:28:32 UTC

Ok. just want to be clear on 2 questions..

Do I have to do anything except keep BOINC updated and will I need to join a new project?
If you don't touch it, you can't break it.
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Message 1830758 - Posted: 16 Nov 2016, 2:33:55 UTC - in response to Message 1830724.  

sorry bud..it got the browser wrong. ;-D
If you don't touch it, you can't break it.
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Message 1831491 - Posted: 19 Nov 2016, 22:56:16 UTC

I think it is an outstanding idea to wrap up the current project, and does credit to David Anderson's integrity, not that he needs it I am sure. The present technology has probably done all that it can, and there is no point in spinning wheels (and using energy) unnecessarily. On with the show.
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Message 1831572 - Posted: 20 Nov 2016, 14:25:38 UTC - in response to Message 1831491.  

I think it is an outstanding idea to wrap up the current project, and does credit to David Anderson's integrity, not that he needs it I am sure. The present technology has probably done all that it can, and there is no point in spinning wheels (and using energy) unnecessarily. On with the show.

There is no "spinning wheels unnessarily" cause continuing data accumulation at least increase robustness of results and sensitivity of search too.
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Message 1831583 - Posted: 20 Nov 2016, 15:06:22 UTC

Phase 1 ends, phase 2 begins. Just carry on folks. I have for 16 years now, my anni was yesterday :-)
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Message 1831589 - Posted: 20 Nov 2016, 15:23:11 UTC - in response to Message 1831572.  

There is no "spinning wheels unnessarily" cause continuing data accumulation at least increase robustness of results and sensitivity of search too.

But I think it will be far more productive to use better telescopes and frequencies more suited to the search. I limit my contribution now because I think it is unlikely to be worth the electricity re-doing the same old thing more or less. When the new stuff gets online, that will be worth considering.
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Message 1831610 - Posted: 20 Nov 2016, 17:40:01 UTC

Also the new data sources provide views of parts of the sky that haven't been surveyed yet. This is particularly true for telescopes in the Southern Hemisphere, and at high latitudes (northern), both of which are unreachable by the Arecibo telescope.
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Message 1831635 - Posted: 20 Nov 2016, 22:10:52 UTC - in response to Message 1831589.  

There is no "spinning wheels unnessarily" cause continuing data accumulation at least increase robustness of results and sensitivity of search too.

But I think it will be far more productive to use better telescopes and frequencies more suited to the search. I limit my contribution now because I think it is unlikely to be worth the electricity re-doing the same old thing more or less. When the new stuff gets online, that will be worth considering.

It's all very subjective.
Some peoples think to spend anything on "green mans" is waste of time, some don't.
Better telescopes? Like what? Better frequencies? Again, like what? Any new ideas with good ground what freq range we should use instead of current one?
New telescopes not considerably "better". They add new sources of data. So we can accumulate more and increase result robustness and sensitivity more.
Time average <=> ensemble average.
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Message 1831636 - Posted: 20 Nov 2016, 22:11:28 UTC - in response to Message 1831610.  

Also the new data sources provide views of parts of the sky that haven't been surveyed yet. This is particularly true for telescopes in the Southern Hemisphere, and at high latitudes (northern), both of which are unreachable by the Arecibo telescope.

That's new addition indeed.
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Message 1831748 - Posted: 21 Nov 2016, 16:10:17 UTC

Effelsberg radio telescope in Germany has a 100 meters steerable antenna. Sardinia telescope in Sardinia has a 64 meters dish with adaptive optics. They both could give data up North.
Tullio
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Message 1831750 - Posted: 21 Nov 2016, 16:26:57 UTC

Yes guys, I fully accept that there are other telescopes than Arecibo and Green Bank, that we could get data from. But as DA has succinctly said. we simply don't have the back end processing power to deal with data received. In any case we only piggy back on where the scopes are pointing, we have no input as to where that might be.
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Message 1831784 - Posted: 21 Nov 2016, 20:35:56 UTC

But as DA has succinctly said. we simply don't have the back end processing power to deal with data received


It's incredible with so many people involved in this project, so many high end CPU's and GPU's and we can't keep up with data collected?
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Message 1831786 - Posted: 21 Nov 2016, 20:51:28 UTC - in response to Message 1831784.  
Last modified: 21 Nov 2016, 20:53:50 UTC

But as DA has succinctly said. we simply don't have the back end processing power to deal with data received


It's incredible with so many people involved in this project, so many high end CPU's and GPU's and we can't keep up with data collected?

The amount of Credit Seti pays is bugger all compared to other projects, so those with the big hardware crunch for other projects, the big crunchers still here are those that are doing more for interest in the project than for credit.
If Seti gave out credit that was at least on par with other projects, there would be a big influx of computing power to this project.

Also the latest GPU hardware has gotten a long way head of the development of applications that can take advantage of it. The SoG application is one example of current work underway to make better use of the more recent hardware, but it still has a way to go.
Improved applications alone could result in a 5-10 times improvement in processing ability from the supported hardware.
Credit that's on par with other projects could more than double the number of active hosts, many of them being high powered systems.

EDIT- and as we've seen lately, Seti is having trouble supporting the current load. How well would it cope with twice the number of users or 5-10 times the WUs being crunched per hour?
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Message 1831787 - Posted: 21 Nov 2016, 20:51:56 UTC - in response to Message 1831750.  

Yes guys, I fully accept that there are other telescopes than Arecibo and Green Bank, that we could get data from. But as DA has succinctly said. we simply don't have the back end processing power to deal with data received. In any case we only piggy back on where the scopes are pointing, we have no input as to where that might be.

Only way to do that is to get a lot of Gamers in this show...they have some serious punching in those GPUs!

But again, someone needs to make some PR stunt for that! & nobody is not doing a thing... :/

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Message 1831816 - Posted: 21 Nov 2016, 23:49:56 UTC

From what I read Nebula is going to run on a UNIX cluster, not on a variety of HW/SW architectures like the front-end SETI@home.
Tullio
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