Back Midas Rome Roody Rootana
  Midas DAQ System  Not logged in ELOG logo
Entry  30 Jan 2025, Pavel Murat, Forum, converting non-MIDAS slow control data into MIDAS history format ? 
    Reply  31 Jan 2025, Pavel Murat, Forum, converting non-MIDAS slow control data into MIDAS history format ? 
    Reply  01 Feb 2025, Pavel Murat, Bug Report, MIDAS history system not using the event timestamps ? test_frontend.pyval_nightly.csv
       Reply  01 Apr 2025, Pavel Murat, Bug Report, MIDAS history system not using the event timestamps ? 
          Reply  01 Apr 2025, Konstantin Olchanski, Bug Report, MIDAS history system not using the event timestamps ? 
             Reply  02 Apr 2025, Pavel Murat, Bug Report, MIDAS history system not using the event timestamps ? 
                Reply  02 Apr 2025, Konstantin Olchanski, Bug Report, MIDAS history system not using the event timestamps ? 
Message ID: 3023     Entry time: 02 Apr 2025     In reply to: 3022
Author: Konstantin Olchanski 
Topic: Bug Report 
Subject: MIDAS history system not using the event timestamps ? 
> > You can always include your "true" data timestamp as the first value in your data.
> 
> Are you saying that if the first data word of a history event were a timestamp, 
> the MIDAS history system, when plotting the time dependencies, would use that timestamp 
> instead of the mlogger timestamp?
>

you are correct, midas knows nothing about what you put in the history data.

what I suggested is: if you want your true data timestamp recorded in the history,
you can put it into the history data yourself, and I suggested using the 1st value,
but you can also make it the last value or the 10th value, it is up to you.

for making history plots, the history timestamp is used, as you wrote and I confirmed,
this timestamp is generated by mlogger.

what is not clear to me is why this is a problem? do you see a big difference between the 
true data timestamp and the mlogger data timestamp? bigger than 1 second? (this would change 
the shape of "last 10 minutes" plots (600 seconds). bigger than 1 minute? (this would change 
the shape of "last 1 hour plots" (60 minutes, 3600 seconds).

that said, note that we currently store the timestamp as a DWORD 32-bit UNIX time value 
which will overflow in 2038 and which is quickly becoming incompatible with the ongoing 
switch to 64-bit time_t. Ubuntu-24 already build a large number of system libraries with 64-
bit time_t and building MIDAS with 32-bit time_t may soon become as difficult as building 
32-bit MIDAS for 32-bit i686 VME processors. we have to move with the times.

what it means is that the history system data format will have to be updated to 64-bit 
time_t and at the same time, we may try to change the timestamp from mlogger-generated to 
frontend-generated.

but it is still not clear to me how that helps you, because the frontend-generated timestamp 
is not the true data timestamp that you wanted. (and only you know what the true data 
timestamp is and where it comes from and how to tell it to MIDAS).

K.O.
ELOG V3.1.4-2e1708b5