 28 Jan 2024, Konstantin Olchanski, Forum, number of entries in a given ODB subdirectory ?
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Very good question. It exposes a very nasty problem, the race condition between "ls" and "rm". While you are
looping over directory entries, somebody else is completely permitted to remove one of the files (or add more
files), making the output of "ls" incorrect (contains non-existant/removed files, does not contain newly added
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28 Jan 2024, Konstantin Olchanski, Forum, History tags
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> This part of the system has been designed by KO, so he should reply here.
That's right. Some of this stuff is historical gibberish that is no longer needed
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28 Jan 2024, Konstantin Olchanski, Forum, a scroll option for "add history variables" window?
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> > Have you updated to the current midas version? This issue has been fixed a while ago.
>
> Hi Stefan, thanks a lot! I pulled from the head, and the scrolling works now. -- regards, Pasha
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28 Jan 2024, Konstantin Olchanski, Forum, dump history FILE files
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$ cat mhf_1697445335_20231016_run_transitions.dat
event name: [Run transitions], time [1697445335]
tag: tag: /DWORD 1 4 /timestamp
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28 Jan 2024, Konstantin Olchanski, Forum, slow control frontends - how much do they sleep and how often their drivers are called?
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> I have implemented a number of slow control frontends which are directed to update the
> history once in every 10 sec, and they do just that.
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28 Jan 2024, Konstantin Olchanski, Forum, the logic of handling history variables ?
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MIDAS history is very simple:
from your frontend, your write your history data to ODB /eq/xxx/variables (see below)
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28 Jan 2024, Stefan Ritt, Forum, number of entries in a given ODB subdirectory ? 
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I guess you won't change your FPGA configuration just when you start a run, so I don't consider the race
condition very crucial (although KO is correct, it it there).
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29 Jan 2024, Pavel Murat, Forum, number of entries in a given ODB subdirectory ?
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Hi Stefan, Konstantin,
thanks a lot for your responses - they are very teaching and it is good to have them archived in the forum.
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29 Jan 2024, Pavel Murat, Forum, a scroll option for "add history variables" window?
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> If you have some ideas on how to better present 100500 history variables, please shout out!
let me share some thoughts. In a particular case which lead to the original posting,
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29 Jan 2024, Konstantin Olchanski, Forum, number of entries in a given ODB subdirectory ?
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> https://chat.openai.com/share/d927c78d-9914-4413-ab5e-3b0e5d173132
>
> Please note that you never can be 100% sure that the code from a LLM is correct
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29 Jan 2024, Konstantin Olchanski, Forum, a scroll option for "add history variables" window?
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familiar situation, "too much data", you dice t or slice it, still too much. BTW, you can try to generate history
plot ODB entries from your program instead of from the history plot editor. K.O. |
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03 Feb 2024, Pavel Murat, Forum, number of entries in a given ODB subdirectory ?
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Konstantin is right: KEY.num_values is not the same as the number of subkeys (should it be ?)
For those looking for an example in the future, I attach a working piece of code converted
from the ChatGPT example, together with its printout.
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 05 Feb 2024, Pavel Murat, Forum, forbidden equipment names ?
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Dear MIDAS experts,
I have multiple daq nodes with two data receiving FPGAs on the PCIe bus each.
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08 Feb 2024, Stefan Ritt, Forum, number of entries in a given ODB subdirectory ?
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> Konstantin is right: KEY.num_values is not the same as the number of subkeys (should it be ?)
For ODB keys of type TID_KEY, the value num_values IS the number of subkeys. The only issue here is
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11 Feb 2024, Pavel Murat, Forum, number of entries in a given ODB subdirectory ?
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> For ODB keys of type TID_KEY, the value num_values IS the number of subkeys.
this logic makes sense, however it doesn't seem to be consistent with the printout of the test example
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13 Feb 2024, Stefan Ritt, Forum, number of entries in a given ODB subdirectory ?
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> > For ODB keys of type TID_KEY, the value num_values IS the number of subkeys.
>
> this logic makes sense, however it doesn't seem to be consistent with the printout of the test example
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13 Feb 2024, Konstantin Olchanski, Forum, forbidden equipment names ?
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> equipment names are 'mu2edaq09:DTC0' and 'mu2edaq09:DTC1'
I think all names permitted for ODB keys are allowed as equipment names, any valid UTF-8,
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15 Feb 2024, Konstantin Olchanski, Forum, number of entries in a given ODB subdirectory ?
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> > > For ODB keys of type TID_KEY, the value num_values IS the number of subkeys.
> >
> > this logic makes sense, however it doesn't seem to be consistent with the printout of the test example
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15 Feb 2024, Konstantin Olchanski, Forum, number of entries in a given ODB subdirectory ?
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> > You are right, num_values is always 1 for TID_KEYS. The number of subkeys is stored in
> > ((KEYLIST *) ((char *)pheader + pkey->data))->num_keys
> > Maybe we should add a function to return this. But so far db_enum_key() was enough.
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15 Feb 2024, Stefan Ritt, Forum, number of entries in a given ODB subdirectory ?
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> Hmm... is there any use case where you want to know the number of directory entries, but you will not iterate
> over them later?
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