[Difx-users] 【警告：フリーメールからの発信です。】 Re: [Difx-developers] INQUIRY: Processing correlation environment {External} {External}

[西 健宏]

Dear Adam,

Thank you for your kind reply.
Your comments and insights are very helpful to us.

Regarding your questions, we are currently checking with our system engineer, and it may take us a little more time to gather the necessary information.
We would appreciate your patience, and we will get back to you once we are ready to respond all the items on your check list.

Thank you for your continued support.

Best regards,
Takehiro
GSI

---------------------------------------------------------------
Takehiro Nishi
Space Geodesy Division
Geodetic Department
Geospatial Information Authority of Japan (GSI)
E-mail: nishi-t96pc at mlit.go.jp
---------------------------------------------------------------



-----Original Message-----
From: Adam Deller <adeller at astro.swin.edu.au> 
Sent: Monday, July 6, 2026 7:56 PM
To: 西 健宏 <nishi-t96pc at mlit.go.jp>
Cc: difx-users at listmgr.nrao.edu; difx-developers at nrao.edu; 古居 晴菜 <furui-h96pd at mlit.go.jp>; 原 哲也 <hara-t96xs at mlit.go.jp>
Subject: 【警告：フリーメールからの発信です。】 Re: [Difx-developers] INQUIRY: Processing correlation environment {External}

Hi Takehiro,

Generally speaking, DiFX is pretty robust to having servers with different capabilities, since the time division multiplexing that is used will happily allocate fewer subintegrations to the slower nodes and more to the faster ones. If the throughput does not go up when you add more processing resources, you are not compute bound, but must instead be either:

1) input voltage read bound;
2) output visibility write bound; or
3) network I/O bound (either a) in the voltage send from the datastream reading nodes, or b) in the visibility subintegration assembly at the manager node)

It would be fairly rare for case 2) to be the problem, unless you have short integration times, many baselines, and many channels. If you have a decent network, and you are not doing very short subintegrations with lots of channels, it would also be unusual for case 3b) to be the problem.  So that leaves the voltage data read or send - either getting it off disk in the first place, or away from the read node to the processing nodes.

Can you let us know what your correlator topology is? Is this reading from commodity disk, Mark5/Mark6, or...? What hardware are the datastream nodes running on, and what network connectivity do they have? And what is the read rate that is being achieved (i.e., what is the per-antenna datarate, and the correlation speed-up factor [correlate time divided by obs time for a given job]?)

Cheers,
Adam

On Mon, 6 Jul 2026 at 20:47, 西 健宏 via Difx-developers <difx-developers at listmgr.nrao.edu <mailto:difx-developers at listmgr.nrao.edu> > wrote:


	Dear colleagues,
	
	Hello.
	My name is Takehiro Nishi, in the Geospatial Information Authority of Japan (GSI).
	GSI is responsible for correlating some of the geodetic VLBI sessions of IVS.
	
	I'm writing to inquire about processing correlation environment.
	
	Currently, GSI is trying to improve the processing speed of "DiFX", since the processing time didn’t improve when we added three new servers for distributed processing. 
	We need to optimize our system, but we are not sure where the bottle neck is.
	Therefore, I would appreciate it if you could inform us of your processing environment to help our investigation as below:
	
	        ・the number of processes written in .machines files     : 
	        ・the number of threads written in .threads files                : 
	        ・the capacity of memory for each server                 : 
	        ・the total number of cores                              : 
	        ・the total number of processing servers                 : 
	        ・Are the number of cores and memory on the servers uniform, or are they varied?
	                :
	
	Thank you for your cooperation.
	
	
	Best regards,
	Takehiro
	GSI
	
	---------------------------------------------------------------
	Takehiro Nishi
	Space Geodesy Division
	Geodetic Department
	Geospatial Information Authority of Japan (GSI)
	E-mail: nishi-t96pc at mlit.go.jp <mailto:nishi-t96pc at mlit.go.jp> 
	---------------------------------------------------------------
	
	
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-- 

!=============================================================!

Prof. Adam Deller         
Centre for Astrophysics & Supercomputing 
Swinburne University of Technology    
John St, Hawthorn VIC 3122 Australia
phone: +61 3 9214 5307
fax: +61 3 9214 8797
!=============================================================!