Astropulse / Radar Blanking / Downtime


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Message 1044527 - Posted: 28 Oct 2010, 21:47:22 UTC

While we are all waiting for the new servers to come, would it be possible to have some thoughts on the way Astropulse handles radar blanking in the client?

And if there would be a more efficient way?

At the moment radar blanked data is replaced by random numbers with uniform distribution. This is done for each of the 888 dm_chunk_small loops.

And this takes a very long time - especially for heavy blanked units, because a lot of double precision mul, div and log functions are used.

(1) Would it be possible to use some sort of lookup table with, up to, state.datasize pre-generated random numbers?

or, better:

(2) "Do the radar removal exactly the same way they do it pre-split at the project. That is, after reading the raw data and figuring out which parts should be replaced, the replacement data overwrites those parts of the raw data. Subsequent processing treats all data as real. The advantage is that rather than doing replacement for each of the 888 dm_chunk_small loops it's only done once, and done linearly through the raw data rather than on 50% overlapped data chunks; it ought to reduce the time spent on removing radar by about a factor of 1600." (quoting Josef W. Segur / Lunatics board)

Especially on the GPU ATI build runtime would be dramatically reduced.

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Message 1044583 - Posted: 28 Oct 2010, 23:23:48 UTC - in response to Message 1044527.

Hi Frizz,

I had exchanged a few messages with Josef Segur about this a while back. I was hoping that the use of the new software radar blanker would render the blanker in the client totally unnecessary. I haven't actually had time to figure out if it has. I'll have to take a look at how often the client blanker kicks in and what the average fraction blanked is on recent workunits.

Eric

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Message 1044592 - Posted: 28 Oct 2010, 23:37:34 UTC - in response to Message 1044583.
Last modified: 28 Oct 2010, 23:39:12 UTC

Hello Eric,

based on my observations of a few Hundred Workunits over the last 1/2 year I would say only about 20% are without blanking. The rest has low to medium blanking (some units almost 100% though :) .

cheers,
Frizz

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Message 1051845 - Posted: 29 Nov 2010, 12:39:03 UTC - in response to Message 1044583.


I was hoping that the use of the new software radar blanker would render the blanker in the client totally unnecessary. I haven't actually had time ...


After the outage, can we expect to get way less blanked units?

Background: The software blanker is really starting to become showstopper for further accelerated GPU apps.

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Message 1051874 - Posted: 29 Nov 2010, 17:02:05 UTC - in response to Message 1051845.

I would love to see this happen. Blanking is what currently slows down the ATI app. removing the data would certainly speed up the processing of work
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Message 1064811 - Posted: 9 Jan 2011, 0:44:20 UTC

Doesn't (radar) blanking kill off the possible signal as well?

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Message 1064835 - Posted: 9 Jan 2011, 2:31:55 UTC - in response to Message 1064811.

you understand that the signal would end up being buried under the local radar signal which is so strong that it would blot out anything worth looking at anyway. Blanking an area removes the offending signal. Yes we won't see ET if he's sending at that particular time and in that particular direction.
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Message 1064894 - Posted: 9 Jan 2011, 8:39:26 UTC - in response to Message 1064811.

Doesn't (radar) blanking kill off the possible signal as well?


Yes, it does.

But that's not the "problem". The reason why I started this thread is: There are maybe *better* ways to do this blanking. Currently generating white noise, which replaces the RFI parts (-> blanks them), is very compute-intensive.

Especially on the ATI GPU client units with blanking run 2x, 3x, ... times slower.

It makes no sense IMHO that blanking takes more time than the actual data analysis.
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Message 1066914 - Posted: 15 Jan 2011, 10:33:55 UTC - in response to Message 1044583.
Last modified: 15 Jan 2011, 10:39:07 UTC

I was hoping that the use of the new software radar blanker would render the blanker in the client totally unnecessary. ...
Eric


After taking a look at my last couple of work units (200+) I still see lots of blanking. The three ones that are currently running on my system have 67%, 55% and 85% blanking.

Question: How does this "software radar blanker" that you mentioned work? Since blanking is such a compute intensive task. E.g. for a heavy blanked tasks, the GPU Astropulse client spends about 3x as much time to do the blanking than on the actual signal analysis. How can/could this "software radar blanker" handle ALL units that are sent out to us crunchers at once?
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Message 1068685 - Posted: 20 Jan 2011, 19:49:35 UTC

All this talk of blanking... Well, nevermind.

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Message boards : SETI@home Science : Astropulse / Radar Blanking / Downtime

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