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<== Date ==> <== Thread ==>

Subject: RE: a question about sequencer
From: Mark Rivers <rivers@cars.uchicago.edu>
To: wux <wux@ihep.ac.cn>, tech-talk <tech-talk@aps.anl.gov>
Date: Fri, 6 Apr 2012 11:50:04 +0000
The answer depends on the syntax of the pvPut in your .st program.

If you just do 

pvPut(recordA)

i.e. without the SYNC option then the pvPut completes as soon as the value is written, and does not wait for the record to complete processing.  In this case the order of processing of record D due to the pvPut is not well determined, it depends on how long it takes records A, B and C to process.   The order could be A, D, B, C, D, but that is not guaranteed.

However, if you do 

pvPut(recordA, SYNC)

then the pvPut does not return until recordA completes processing, and that includes all other records that processed as a direct result of recordA processing.  This means in your case that it will wait until recordD completes as well.  So in this case when the .st program does the pvPut to recordA it will not return until recordD has completed, and the processing sequence will be A, B, C, D, D.

Cheers,
Mark

________________________________________
From: tech-talk-bounces@aps.anl.gov [tech-talk-bounces@aps.anl.gov] on behalf of wux [wux@ihep.ac.cn]
Sent: Thursday, April 05, 2012 10:49 PM
To: tech-talk
Subject: a question about sequencer

Hi all,
        Suppose there were record A forward link record B and record B forward link record C and record D. In the .st program, if pvPut record A, then pvPut record D, how will the program act? Process record A then process record B and process record C and process record D fianally or proces record A then process record D...? I'm sorry for my poor english

Cheers!
Xuan Wu


--------------
Xuan Wu
Control Group
Accelerator Center
Institute of High Energy Physics,Chinese Academy of Sciences
Yuquan Road 19B,Shijingshan District
P.O.Box:918(10)
100049,Beijing,P.R.China
Tel:86-10-88235484
Mobile Phone:86-10-13426200386



References:
a question about sequencer wux

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