I guess the simplest way to do that without breaking with existing code is to change the 
second number to a float. So a

WAIT SECONDS, 1

will still work, and you can then write

WAIT SECONDS, 0.01

to get a 10 ms wait. Would that work for you?

Stefan

> This would work fine in principle, but isn't implemented in the current MIDAS sequencer as we understand it.  (We tried!) Is your proposal to rewrite the sequencer 
> to allow fractional waits?  Right now the code seems to store the start_time as a DWORD and uses atoi to parse the wait time, and uses ss_time (which seems only get
> the time to the nearest second) to fetch the time.

No it's not implemented, was just my idea. If it would work for you, I can implement it in the next couple of days.

Stefan

While I will do it, i'm not sure if this is what you want. If I understand correctly, some process gets triggered and then writes some values to the ODB, then the sequencer 
should continue. Putting a wait there is dangerous. Maybe your process always takes like 10-20 ms, so you put a wait of let's say 100ms, and things are fine with you. Your 
script runs many days, but then once in a while your machine is on heavy load because someone starts a web browser, and your process takes 110ms, and you script crashes.

I would rather go following path: put a "done" flag in the ODB, which is the last one which gets set by your process. Then the sequencer does a 

WAIT ODBvalue, /path/value, =, 1

which will work always, independend of the delay of your process.

Stefan

Ok, I implemented the float second wait function. Internally it works in ms, so the maximum resolution is 0.001 s.

Best,
Stefan

Ok, here is the complete code to reproduce the problem. Load parameter_test.msl which includes functions.msl. From the screenshot you see the variables containing 
garbage, and you also see that from the ODB screenshot. For completeness, I added Sequencer.json which contains the whole sequencer tree.

The interesting thing is that this works sometimes, and sometimes not. I'm not sure if this in the GUI or in the sequencer program, so we have to sort out who can 
fix it ;-)

Best,
Stefan

The tinyexpr library I use to evaluate expressions does not support boolean operations. I would have to switch to the newer 
tineyexpr-plusplus version, which also has much richer functionality:

https://github.com/Blake-Madden/tinyexpr-plusplus/blob/tinyexpr%2B%2B/TinyExprChanges.md

Unfortunately it requires C++17, and at the moment we limit MIDAS to C++11, meaning we would break this requirement. I 
believe at the moment there are still some experiments (mainly at TRIUMF) which are stuck to older OS and therefore cannot 
switch to C++17, but hopefully this will change over time.

Stefan

Ahh, that rings a bell:

1) JS opens start dialog box
2) User enters parameters and presses start
3) JS writes parameters
4) JS starts sequencer
5) Sequencer copies parameters to variables

Now how do you handle 3) and 4). Just issue two mjsonrpc commands together? What then could happen is that 4) is executed before 3) and we get the garbage.
You have to do 3) and WAIT for the return ("then" in the JS promise), and only then issue 4) from there.

Stefan

Seems to me like the problem happens less frequently, but I still see it (1 out of 5 or so). The fact that /Sequencer/Params/Value is empty tells me that the GUI 
has the problem and not the sequencer side.

Stefan

Indeed there was a sleep(100ms) in the sequencer in each loop. I reduced it now to 10ms. I need at least 10ms since otherwise 
the sequencer would run in an infinite loop during the wait and burn 100% CPU. The smallest time slice on Linux to sleep is 
10ms, so that's why I set it to that. Give it a try.

Stefan

Actually I realized that a 1ms wait still works, so I reduced it to that.

Stefan

This is a common problem I also encountered in the past. You get a low-level ODB access error (could also be a read of a non-existing key) and you 
have no idea where this comes from. Could be the alarm system, a mhttpd web page, even some user code in a front-end over which the midas library 
has no control.

One option would be to add a complete stack dump to each of these error (ROOT does something like that), but I hear already people shouting "my 
midas.log is flooded with stack dumps!". So what I do in this case is I run a midas program in the debugger and set a breakpoint (in your case at 
odb.cxx:6967). If the breakpoint triggers, I inspect the stack and find out where this comes from.

Not that I print a stack dump for such error in the odbxx API. This goes to stdout, not the midas log, and it helped me in the past. Unfortunately 
stack dumps work only under linux (not MacOSX), and they do not contain all information a debugger can show you.

It is not true that alarm conditions are evaluated when the alarm system is off. I just tried and it works fine. The code is here:

alarm.cxx:591

      /* check global alarm flag */
      flag = TRUE;
      size = sizeof(flag);
      db_get_value(hDB, 0, "/Alarms/Alarm system active", &flag, &size, TID_BOOL, TRUE);
      if (!flag)
         return AL_SUCCESS;

so no idea why you see this error if you correctly st "Alarm system active" to false.

Stefan

For everybody using EPICS: There is now a new system called MSetPoint (Midas Set Point) to control whole beamlines via EPICS.
It's under midas/msetpoint and the documentation is here:

   https://bitbucket.org/tmidas/midas/wiki/MSetPoint

It is basically an EPICS frontend and two custom pages. The special thing is that the EPICS elements are not hardcoded in
the frontend but come from the ODB. There is even an editor for the beamline elements (second custom page). By loading different
ODB settings, one can switch easily between completely different beamlines without having to recompile the frontend. The system
can be operated standalone (all other MIDAS pages do not appear), or as a custom page in a normal midas setup. At PSI, this
system is now used as the standard editor for our beamlines.

Attached and example screen.

Stefan

For everybody using EPICS: There is now a new system called MSetPoint (Midas Set Point) to control whole beamlines via EPICS.
It's under midas/msetpoint and the documentation is here:

   https://bitbucket.org/tmidas/midas/wiki/MSetPoint

It is basically an EPICS frontend and two custom pages. The special thing is that the EPICS elements are not hardcoded in
the frontend but come from the ODB. There is even an editor for the beamline elements (second custom page). By loading different
ODB settings, one can switch easily between completely different beamlines without having to recompile the frontend. The system
can be operated standalone (all other MIDAS pages do not appear), or as a custom page in a normal midas setup. At PSI, this
system is now used as the standard editor for our beamlines.

Attached and example screen.

Stefan

Taht's strange. I always was under the impression that .odb files are loaded relatively to the current location in 
the ODB. The behaviour should not be different for different data formats, so I agree to change the .odb loading to 
behave like the .xml and .json save/load.

Stefan

I fixed that and committed the change to megon02, just reload your browser. I also set ymin and ymax of the Vacuum plot to meaningful 
values (not to zero!).

Stefan

> I noticed that a check was added to mfe.cxx in 1961af0d6:
> 
> +      /* check for consistent common settings */
> +      if ((eq_info->read_on & RO_STOPPED) &&
> +          (eq_info->eq_type == EQ_POLLED ||
> +           eq_info->eq_type == EQ_INTERRUPT ||
> +           eq_info->eq_type == EQ_MULTITHREAD ||
> +           eq_info->eq_type == EQ_USER)) {
> +         cm_msg(MERROR, "register_equipment", "Events \"%s\" cannot be read when run is stopped (RO_STOPPED flag)", equipment[idx].name);
> +         return 0;
> +      }
> 
> 
> Can someone explain the purpose of this check and error message? Perhaps it
> was put in place with only DAQ FEs, not SC FEs in mind? And should the 
> documentation in the wiki actually be "s/Before stopping run/While run is stopped/"?

Indeed you have two types of events handled by mfe.cxx: Slow control events (EQ_SLOW or EQ_PRIODIC) and triggered events (EQ_POLLED or 
EQ_INTERRUPT or EQ_MULTITHREAD or EQ_USER). For slow control events it can make sense to read them also when the run is stopped, that's why you 
can specify RO_STOPPED or RO_ALWAYS. This does however not make sense for triggered events. Reading triggered events when the run is stopped 
invalidates the concept of runs (= read triggered events only during a run). We had cases where people mixed this up, so the warning was added. 
If you have a slow control event you want to read when the run is stopped, make sure it is of type EQ_SLOW or EQ_PERIODIC.

Stefan

I don't see any bad side effects at the moment, so I accepted the changes and committed them.

Stefan