> cmake check and mate in 1 move. please help.
> -std=c++11 and -std=c++14 collision...

I have a solution implemented for this, I am not happy with it, Stefan is not happy with it. See 
discussion: https://bitbucket.org/tmidas/midas/commits/50a15aa70a4fe3927764605e8964b55a3bb1732b

K.O.

> > cmake check and mate in 1 move. please help.
> > -std=c++11 and -std=c++14 collision...
> 
> I have a solution implemented for this, I am not happy with it, Stefan is not happy with it. See 
> discussion: https://bitbucket.org/tmidas/midas/commits/50a15aa70a4fe3927764605e8964b55a3bb1732b
>

I figured it out, solution is to use:

target_compile_features(midas PUBLIC cxx_std_11)

this is how it works:

- centos-7 (g++ has c++11 off by default): -std=gnu++11 is added automatically (not -std=c++11, but 
probably correct, as some c++11 functions were available as gnu extensions)
- ubuntu-20.04 LTS without ROOT: nothing added (I guess correct, g++ has c++11 is enabled by default)
- ubuntu-20.04 LTS with -std=c++14 from ROOT: nothing added, c++14 as requested by ROOT is in affect.
- macos without ROOT: -std=gnu++11 is added automatically
- macos with -std=c++11 from ROOT: ditto, so both -std=c++11 and -std=gnu++11 are present in this order, 
wrong-ish, but works.

and good luck figuring this out just from cmake documentation:
https://cmake.org/cmake/help/latest/command/target_compile_features.html

K.O.

Moving in the direction of this proposal. History plot editor is updated according to it. Remaining missing piece is the "show 
raw value" buttons and code behind them.

Changes:

- "show factor and offset" moved to the top of the page, "off" by default
- factor and offset (if not zero) are automatically migrated to the formula field (if it is empty), one needs to save the panel 
for this to take effect.

K.O.


> > I am updating the history plots.
> > So the idea is to use this computation:
> > y_position_on_plot = offset + factor*(formula(history_value) - voffset)
> 
> Stefan and myself did some brain storming on zoom. Writing it down the way I remember it.
> 
> - we distilled the gist of the problem - the numerical values we show in the plot labels and in hover-over-the-graph
> are before formula is applied or after the formula is applied?
> 
> - I suggested a universal solution using a double formula: use formula1 for one case;
>   use formula2 for the other case;
>   use formula1 for "physics calibration", use formula2 for factor and offset for composite plots:
>      numeric_value = formula1(history_value)
>      plotted_value = formula2(numeric_value)
> 
> - we agree that this is way too complicated, difficult to explain and difficult to coherently present in the history editor
> 
> - Stefan suggested a simple solution, a checkbox labeled "show raw value" next to each history variable. by default, the 
> value after the formula is plotted and displayed. if checked, the raw value (before the formula) is displayed, and the 
> value after the formula is plotted. (so this works the same as the factor and offset on the old history plots).
> 
> - if "show raw value" is enabled, the numerical values shown will be inconsistent against the labels on the vertical axis. 
> Our solution it to turn the axis labels off. (for composite plots, like oscillator frequency in Hz vs oscillator 
> temperature in degC, both scaled to see their correlation, the vertical axis is unit-less "arbitrary units", of course)
> 
> - to simplify migration of old history plots that use custom factor and offset settings, we think in the direction of 
> automatically moving them to the "formula". (factor=2, offset=10 automatically populates formula with "2*x+10", "show raw 
> value" checked/enabled). Thus we can avoid implementing factor and offset in the new history code (an unwelcome 
> complication).
> 
> - I think this covers all the use cases I have seen in the past, so we will move in this direction.
> 
> K.O.

> Moving in the direction of this proposal. Remaining missing piece is the "show 
> raw value" buttons and code behind them.

added "show raw value" button, updated on-page instructions.

I think this is the final layout of the history panel editor, conversion
to html+javascript will be done "as is". If you have suggestions to improve
the layout (add/remove/move things around, etc), please shoult out (on the elog
here or by direct email to me).

I am thinking in the direction of changing the control flow of the history editor:

- midas "history" manu button click redirects to
- current history panel selection (with checkbox to open old history plots), click on "new plot" button redirects to
- new page for creating new plots. this will present a list of all history variables, click on variable name creates a new history 
panel containing just this one variable and redirects to it.

In other words, to see the history for any history variable:
- click on "history" menu button
- click on "new"
- click on desired history variable
- see this history plot

From here, click on the "wheel" button to open the existing history panel editor and add any additional variables, change settings, 
etc.

In the history panel editor, I am thinking in the direction of replacing the existing drop-down selection of history variables (now 
very workable for large experiments) with an overlay dialog to show all history variables, with checkboxes to select them, basically 
the same history variable select page as described above. Not sure yet how this will work visually.

K.O.

I am looking at the mlogger in the ALPHA anti-hydrogen experiment at CERN. It is 
mysteriously misbehaving during run start and stop.

The problem turns out to be with the select() system call.

The corresponding FD_SET(), FD_ISSET() & co operate on a an array of fixed size 
FD_SETSIZE, value 1024, in my case. But the socket number is 1409, so we overrun 
the FD_SET() array. Ouch.

I see that all uses of select() in midas have no protection against this.

(we should probably move away from select() to newer poll() or whatever it is)

Why does mlogger open so many file descriptors? The usual, scaling problems in the 
history. The old midas history does not reuse file descriptors, so opens the same 
3 history files (.hst, .idx, etc) for each history event. The new FILE history 
opens just one file per history event. But if the number of events is bigger than 
1024, we run into same trouble.

(BTW, the system limit on file descriptors is 4096 on the affected machine, 1024 
on some other machines, see "limit" or "ulimit -a").

K.O.

> [mhttpd,ERROR] [mhttpd.cxx:18886:on_work_complete,ERROR] Should not send response to request from socket 28 to socket 26, abort!
> Can anybody hint me what is going wrong here?
> The bad thing on the crash is, that sometimes it is leading to a "chain-reaction" killing multiple midas frontends, which essentially stop the experiment.

This is my code. I am the culprit. I had a bit of discussion about this with Stefan.

Bottom line is something is rotten in the multithreading code inside mhttpd and under conditions unknown,
it sends the wrong data into the wrong socket. This causes midas web pages to be really confused (RPC replies
processed as CSS file, HTML code processed at RPC replies, a mess), this wrong data is cached by the browser,
so restarting mhttpd does not fix the web pages. So a mess.

I find this is impossible to replicate, and so cannot debug it, cannot fix it. Best I was able to do
is to add a check for socket numbers, and thankfully it catches the condition before web browser caches
become poisoned. So, broken web pages replaced by mhttpd crash.

This situation reinforces my opinion that multi-threading and C++ classes "do not mix" (like H2 and O2 do not mix).
If you write a multithreaded C++ program and it works, good for you, if there is a malfunction, good luck with it,
C++ just does not have any built-in support for debugging typical multithreading problems. I think others have come
to the same conclusion and invented all these new "safe" programming languages, like Rust and Go.

Back to your troubles.

1) If you see a way to replicate this crash, or some way to reliably cause
the crash within 5-10 minutes after starting mhttpd, please let me know. I can work with that
and I wish to fix this problem very much.

2) My "wrong socket" check calls abort() to produce a core dump. In my experience these core dumps
are useless for debugging the present problem. There is just no way to examine the state of each
thread and of each http request using gdb by hand.

3) this abort() causes linux to write a core dump, this takes a long time and I think it causes
other MIDAS program to stop, timeout and die. You can try to fix this by disabling core dumps (set "enable core dumps"
to "false" in ODB and set core dump size limit to 0), or change abort() to exit(). (You can also disable
the "wrong socket" check, but most likely you will not like the result).

4) run mhttpd inside a script: "while (1) { start mhttpd; sleep 1 sec; rinse, repeat; }" (run mhttpd without "-D", yes?)

In other news, the mongoose web server library have a new version available, they again changed their
multithreading scheme (I think it is an improvement). If I update mhttpd to this new version, it is very
likely the code with the "wrong socket" bug will be deleted. (with new bugs added to replace old bugs, of course).

K.O.

test, no email. K.O.

> test, no email. K.O.

test reply, no email. K.O.

> > test, no email. K.O.
> 
> test reply, no email. K.O.

test attachment, no email. K.O.

> > > test, no email. K.O.
> > 
> > test reply, no email. K.O.
> 
> test attachment, no email. K.O.

test email. K.O.

The midas forum software (elogd) was updated to latest version and moved from our old server 
(ladd00.triumf.ca) to our new server (daq00.triumf.ca).

The following URLs should work:

https://daq00.triumf.ca/elog-midas/Midas/ (new URL)
https://midas.triumf.ca/elog/Midas/ (old URL, redirects to daq00)
https://midas.triumf.ca/forum (link from midas wiki)

The configuration on the old server ladd00.triumf.ca is quite tangled between
several virtual hosts and several DNS CNAMEs. I think I got all the redirects
correct and all old URLs and links in old emails & etc still work.

If you see something wrong, please reply to this message here or email me directly.

K.O.

> I adapted our analyzer to compile against the manalyzer included in the midas repo.
> TMReadEvent: error: short read 0 instead of -1193512213

I think this problem is fixed in the latest version of midasio and manalyzer, but this update
was not pulled into midas yet. (Canada is in the middle of a covid wave since December).

What happens is you do not have the gzip library installed on your computer and
your analyzer is built without support for gzip.

The fix is done the hard way, the gzip library is no longer optional, but required.

You do not say what linux you use, so I cannot give exact instructions, but for:
ubuntu: apt -y install libz-dev
centos7: installed by default
centos8: installed by default
debian11/raspbian: same as ubuntu

K.O.

> Dear all, does anyone have an example of for a device driver using modbus or modbus tcp to communicate with a device and willing to share it? Thanks.

I have not seen any modbus devices recently, so all my code and examples are quite old.

Basic modbus/tcp communication driver is in the midas repo:

daq00:midas$ find . | grep -i modbus
./drivers/divers/ModbusTcp.cxx
./drivers/divers/ModbusTcp.h
daq00:midas$ 

This driver worked for communication to a modbus PLC (T2K/ND280/TPC experiment in Japan).

An example program to use this driver and test modbus communication is here:
https://bitbucket.org/expalpha/agdaq/src/master/src/modbus.cxx

Because at the end, we do not have any modbus devices in any recent experiment,
I do not have any example of using this driver in the midas frontend. Sorry.

K.O.

> today I did not get the data into MIDAS. 

Any error messages printed by the frontend? any error message in midas.log? core dumps? crashes?

I do not understand what you mean by "did not get the data into midas". You create events
and send them to a midas event buffer and you do not see them there? With mdump?
Do you see this both connected locally and connected remotely through the mserver?

BTW, I see you are using the mfe.c frontend. Event data handling in mfe.c frontends
is quite convoluted and impossible to straighten out. I recommend that you use
the tmfe c++ frontend instead. Event data handling is much simplified and is easier to debug
compared to the mfe.c frontend. There is examples in the midas repository and there are
tutorials for converting frontends from mfe.c to tmfe posted in this forum here.

BTW, the commit you refer to only changed some html files, could not have affected
your data.

K.O.

> The problem is that eventually some of frontend closed with message 
> :19:22:31.834 2021/12/02 [rootana,INFO] Client 'Sample Frontend38' on buffer 
> 'SYSMSG' removed by cm_periodic_tasks because process pid 9789 does not exist

This messages means what it says. A client was registered with the SYSMSG buffer and this 
client had pid 9789. At some point some other client (rootana, in this case) checked it and 
process pid 9789 was no longer running. (it then proceeded to remove the registration).

There is 2 possibilities:
- simplest: your frontend has crashed. best to debug this by running it inside gdb, wait for 
the crash.
- unlikely: reported pid is bogus, real pid of your frontend is different, the client 
registration in SYSMSG is corrupted. this would indicate massive corruption of midas shared 
memory buffers, not impossible if your frontend misbehaves and writes to random memory 
addresses. ODB has protection against this (normally turned off, easy to enable, set ODB 
"/experiment/protect odb" to yes), shared memory buffers do not have protection against this 
(should be added?).

Do this. When you start your frontend, write down it's pid, when you see the crash message, 
confirm pid number printed is the same. As additional test, run your frontend inside gdb, 
after it crashes, you can print the stack trace, etc.

> 
> in the meantime mserver loggging :
> mserver started interactively
> mserver will listen on TCP port 1175
> double free or corruption (!prev)
> double free or corruption (!prev)
> free(): invalid next size (normal)
> double free or corruption (!prev)
> 

Are these "double free" messages coming from the mserver or from your frontend? (i.e. you run 
them in different terminals, not all in the same terminal?).

If messages are coming from the mserver, this confirms possibility (1),
except that for frontends connected remotely, the pid is the pid of the mserver,
and what we see are crashes of mserver, not crashes of your frontend. These are much harder to 
debug.

You will need to enable core dumps (ODB /Experiment/Enable core dumps set to "y"),
confirm that core dumps work (i.e. "killall -SEGV mserver", observe core files are created
in the directory where you started the mserver), reproduce the crash, run "gdb mserver 
core.NNNN", run "bt" to print the stack trace, post the stack trace here (or email to me 
directly).

>
> I can find some correlation between number of events/event size produced by 
> frontend, cause its failed when its become big enough. 
> 

There is no limit on event size or event rate in midas, you should not see any crash
regardless of what you do. (there is a limit of event size, because an event has
to fit inside an event buffer and event buffer size is limited to 2 GB).

Obviously you hit a bug in mserver that makes it crash. Let's debug it.

One thing to try is set the write cache size to zero and see if your crash goes away. I see
some indication of something rotten in the event buffer code if write cache is enabled. This
is set in ODB "/Eq/XXX/Common/Write Cache Size", set it to zero. (beware recent confusion
where odb settings have no effect depending on value of "equipment_common_overwrite").

>
> frontend scheme is like this:
> 

Best if you use the tmfe c++ frontend, event data handling is much simpler and we do not
have to debug the convoluted old code in mfe.c.

K.O.

>
> poll event time set to 0;
> 
> poll_event{
> //if buffer not transferred return (continue cutting the main buffer)
> //read main buffer from hardware
> //buffer not transfered
> }
> 
> read event{
> // cut the main buffer to subevents (cut one event from main buffer) return;
> //if (last subevent) {buffer transfered ;return}
> }
> 
> What is strange to me that 2 frontends (1 per remote pc) causing this.
> 
> Also, I'm executing one FEcode with -i # flag , put setting eventid in 
> frontend_init , and using SYSTEM buffer for all.
> 
> Is there something I'm missing?
> Thanks. 
> A.

> > 3 LOOP n,4
> > 4   MESSAGE $n,1
> > 5 ENDLOOP
> 
> Indeed you're right. The loop variable runs from 1...n. I fixed that in the documentation.

Shades/ghosts of FORTRAN. c/c++/perl/python loops loop from 0 to n-1.

K.O.

For those curious about CAMAC controllers, this one was built around 2014 to 
replace the aging CAMAC A1/A2 controllers (parallel and serial) in the TRIUMF 
cyclotron controls system (around 50 CAMAC crates). It implements the main
and the auxiliary controller mode (single width and double width modules).

The design predates Altera Cyclone-5 SoC and has separate
ARM processor (TI 335x) and Cyclone-4 FPGA connected by GPMC bus.

ARM processor boots Linux kernel and CentOS-7 userland from an SD card,
FPGA boots from it's own EPCS flash.

User program running on the ARM processor (i.e. a MIDAS frontend)
initiates CAMAC operations, FPGA executes them. Quite simple.

K.O.

Francesco, when you say "writing an event is slow", do you mean it in the frontend
or in the output data file?

Stefan is quite right about the data file, it can take seconds between generating
an event in the frontend and seeing it written to the data file. (if compression
buffers are too big, an event can sit there forever, until pushed out by next events
or by run stop).

But maybe you see this on the frontend side.

What you are looking at is "real time" performance of the frontend and of the linux kernel.

The mfe.c frontend has many problems with real time performance, it can stall and take a long
time between calls to read_event(), for many reasons.

There are ways around that, but it is simpler to switch to the tmfe c++ frontend
that was designed for good real time performance.

In the tmfe frontend, if you use the polled equipment and enable the poll thread,
your frontend will be limited only by the linux kernel real time performance (i.e.
on a single-core CPU, other programs will delay execution of your frontend
and you will see it as long delays (usec, millisec) between calls to your read_event().

Next limit to real time performance (common to mfe.c and tmfe frontends) is the writing
of event data to the midas shared event buffer. One has to lock the shared memory semaphore
and this has to wait until other users of the event buffer finish their reading
or writing and unlock it. Arbitrary amount of time (usec, millisec, sec) can pass.
(there is also problems with "fairness" of the linux semaphores, a different story, again).

Making things more interesting, midas event buffers implement a write cache (default size 100 kbytes),
events smaller than the cache are quickly accumulated (no need to lock the shared memory semaphore),
them flushed to shared memory when cache is full. This is done to reduce the number
of shared memory semaphore locks per event, in the case of very high rate of very small events.

Solution to all this is to use 2 threads: read the data from hardware in one thread and write the data to midas
in a different thread. Between the threads would be an event fifo (circular buffer in mfe.c,
std::deque<EVENT> in tmfe c++ frontends).

For remote connected frontends, things are a bit different. Event data is written directly
into the TCP socket and as long as socket buffers are big enough, there is no real-time delays,
unless SYSTEM buffer is very congested and mserver does not read the TCP socket quickly enough.
So depending on event size, data rate and tcp socket buffer size, the extra 2nd thread
may not be necessary and poll thread real time performance may be good enough.

I hope this clarifies the situation somewhat.

K.O.

> Dear all,
>        I've a frontend writing a quite big bunch of data into a MIDAS bank (16bit output from a 4MP photo camera). 
> I'm experiencing a writing speed problem that I don't understand. When the photo camera is triggered at a low rate (< 2 Hz) 
> writing into the bank takes a very short time for each event (indeed, what I measure is the time to write and go back 
> into the polling function). If I increase the rate to 4 Hz, I see that writing the first two events takes a sort time, 
> but the third event takes a very long time (hundreds of ms), then again the fourth and fifth events are very fast, and 
> the sixth is very slow. If I further increase the rate, every other event is very slow. The problem is not in the readout 
> of the camera, because if I just remove the bank writing and keep the camera readout, the problem disappears. Can you 
> explain this behavior? Is there any way to improve it?
> 
> Below you can also find the code I use to copy the data from the camera buffer into the bank. If you have any suggestion 
> to improve it, it would be really appreciated.
> 
> Thank you very much,
>           Francesco
> 
> 
> 
>   const char* pSrc = (const char*)bufframe.buf;
> 
>   for(int y = 0; y < bufframe.height; y++ ){
> 
>     //Copy one row
>     const unsigned short* pDst = (const unsigned short*)pSrc;
> 
>     //go through the row
>     for(int x = 0; x < bufframe.width; x++ ){
> 
>       WORD tmpData = *pDst++; 
> 
>       *pdata++ = tmpData;
> 
>     }
> 
>     pSrc += bufframe.rowbytes;
> 
>   }
>  

> Francesco, when you say "writing an event is slow", do you mean it in the frontend
> or in the output data file?

Another explanation just occurred to me. We do not know your event size and we do not
know the size of your SYSTEM buffer. But if you have an unlucky combination,
this can happen:

Consider event size is 6 Mbytes, buffer size is 8 Mbytes, enough space for only 1 event.

First event is written quickly (buffer is empty).
Second event will be delayed, there is not enough free space in the buffer, we have
to wait for mlogger to finish reading the first event.

Same thing happens if event size is 3 Mbytes, the first 2 events will write quickly,
writing the 3rd event will be delayed until mlogger does it's thing.

The mlogger reads the SYSTEM buffer "fast" and "quickly", but it can be delayed
for a number of reasons, i.e. handling a history event, a delay writing to disk,
a delay writing to network connected storage, etc.

In general, it is best to size the SYSTEM buffer to hold about 1 second worth
of data (of average size, average rate). If your event size is 4 Mbytes, and you
record them at 10/sec, SYSTEM buffer should be at least 40 Mbytes big. (this is
set in ODB /Experiment/Buffer Sizes). (MIDAS event buffer size is limited to 2 GBytes).

K.O.

> > Shades/ghosts of FORTRAN. c/c++/perl/python loops loop from 0 to n-1.
> 
>    for (i=1 ; i<=10 ; i++);     ;-)

Similar code made big news just recently: (scroll down to the example main() program)

https://blog.qualys.com/vulnerabilities-threat-research/2022/01/25/pwnkit-local-privilege-escalation-
vulnerability-discovered-in-polkits-pkexec-cve-2021-4034

I forget if the FORTRAN rules were "loop once" or "never loop" or if it was different
between Fortran-4, fortran-77, DEC extensions and IBM extension, or if it was a compiler switch.

We should check that we do something reasonable with such loops to zero:

LOOP n,0
   MESSAGE $n,1
ENDLOOP

P.S. Yup. "man g77" option "-fonetrip".

K.O.