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

Subject: Re: matrix multiplication and inversions
From: Matt Rippa via Tech-talk <tech-talk at aps.anl.gov>
To: "Johnson, Andrew N." <anj at anl.gov>
Cc: tech-talk <tech-talk at aps.anl.gov>
Date: Fri, 21 Feb 2020 17:31:27 -1000
I just saw this. To add to the history we successfully upgraded Gemini's primary mirror control system to OSI/RTEMS in 2017. It still uses the devSymb global variable support which was ported to work with RTEMS (thanks Michael Davidsaver). We still haven't moved to the aSub support. If you're interested in any of the details just send me an email.
      
About 25 years ago (wow, was it really?) John Maclean and I devised the controls for the Gemini primary mirror where the IOC did various matrix calculations before passing the results to the dynamic support system actuators via CANbus. We did the maths in subroutine record sub’s using shared global variables to store the small number of large matrices we had to handle, and only used the sub-records to control when the calculations were executed (and to hold scalar parameters and results). We also used waveform records with “devSymb” device support to read and write the shared global variables, although I don’t remember how we synchronized everything to prevent races. The aSub didn’t exist at the time, although Gemini did soon devise the genSub that was its precursor.

Cheers,
-Matt

References:
matrix multiplication and inversions Pearson, Matthew R. via Tech-talk
Re: matrix multiplication and inversions Johnson, Andrew N. via Tech-talk

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