> My name is Soichiro Kuribayashi and I am a Ph.D. student at Kyoto University. 
> I'm a T2K collaborator and working for Super FGD which is new detector in ND280.

Hi! I did much of the DAQ software for the original FGD. I hope I can help.

> For the DAQ of Super FGD, we will run remotely front end part of MIDAS on ZYNQ 
> which is system on chip.

This would be the same as the existing FGD. Inside the FGD DCC is a Virtex4 FPGA
with a 300MHz PPC CPU running Linux from a CompactFlash card (Kentaro-san did this 
part). On this linux system runs the FGD DCC midas frontend. It connects
to the FGD midas instance using the mserver. This frontend executable is
copied to the DCC using "scp", there is no common nfs mounted home directory.

> For this remote control of front end part with mserver, we have to mount home 
> directory of DAQ PC(Cent OS8) on that of Linux on ZYNQ.
> So I wonder if we should use NFS(Network file system) + NIS(Network information 
> service) + autofs for the mounting. Is it correct?

Since you have a bigger SOC and you can run pretty much a complete linux,
I do recommend that you go this route. During development it is very convenient
to have common home directories on the main machine and on the frontend fpga
machines.

But this is not necessary. the midas mserver connection does not require
common (nfs-mounted) home directory, you can copy the files to the frontend
fpga using scp and rsync and you can use the gdb "remote debugger" function.

I can also suggest that on your frontend SOC/FPGA machine, you boot linux
using the "nfs-root" method. This way, the local flash memory only
contains a boot loader (and maybe the linux kernel image, depending on
bootloader limitations). The rest of the linux rootfs can be on your
central development machine. This way management of flash cards,
confusion with different contents of local flash and need to make backups
of frontend machines is much reduced.

If you use a fast SSD and ZFS with deduplication, you will also have good
performance gain (NFS over 1gige network to server with fast SSD works
so much better compared to the very slow SD/MMC/NAND flash).

I can point you to some of my documentation how we do this.

>
> If you have any information or any suggestion for the remote control on chip, 
> please let me know.
> 

I would say you are on a good track. For early development on just one board,
pretty much any way you do it will work, but once you start scaling up
beyound 3-4-5 frontends, you will start seeing benefits from common NFS-mounted
home directories, NFS-root booted linux, etc.

And of course you may want to study the existing ND280/FGD DAQ. I hope you
have access to the running system at Jparc. If not, I have a copy of
pretty much everything (except for running hardware, it is stored in the basement, 
dead) and I can give you access.

P.S. This reminds me that the cascade software from ND280 (they key part
for connecting the FGD, the TPC, the slow controls & etc into one experiment)
was never merged into the midas repository. I opened a ticket for this,
now we will not forget again:

https://bitbucket.org/tmidas/midas/issues/291/import-cascase-frontend-from-t2k-
nd280-fgd

K.O.

Dear Konstantin,

Thank you very much for your reply and detailed information.
I would appreciate if you could help us.

> I can also suggest that on your frontend SOC/FPGA machine, you boot linux
> using the "nfs-root" method. This way, the local flash memory only
> contains a boot loader (and maybe the linux kernel image, depending on
> bootloader limitations). The rest of the linux rootfs can be on your
> central development machine. This way management of flash cards,
> confusion with different contents of local flash and need to make backups
> of frontend machines is much reduced.

As you said, we can run complete Linux (Ubuntu 16) on ZYNQ and I'm using common NFS 
system now. However, I didn't know "nfs-root" method which you mentioned and this method 
seems to be reasonable way to just share linux rootfs.
First of all, I will try this method for simpler system.

> If you use a fast SSD and ZFS with deduplication, you will also have good
> performance gain (NFS over 1gige network to server with fast SSD works
> so much better compared to the very slow SD/MMC/NAND flash).
>
> I can point you to some of my documentation how we do this.

I'm concerned about such performance and I have checked the performance with common NFS 
over gige network and my DAQ PC roughly(data transfer rate ~ O(10) MByte/sec). However, I 
didn't know the ZFS and also how we can have performance gain with a fast SSD and ZFS.
Please let me know your documentation how to do it if possible.

> I would say you are on a good track. For early development on just one board,
> pretty much any way you do it will work, but once you start scaling up
> beyound 3-4-5 frontends, you will start seeing benefits from common NFS-mounted
> home directories, NFS-root booted linux, etc.

I'm developing with just one board and common NFS-mounted now. I'm looking forward to 
seeing such benefits when I will use multiple frontends.
 
> And of course you may want to study the existing ND280/FGD DAQ. I hope you
> have access to the running system at Jparc. If not, I have a copy of
> pretty much everything (except for running hardware, it is stored in the basement, 
> dead) and I can give you access.

I don't have access to the system at Jparc, but Nick has told us where FGD DAQ code is.
Is bellow URL everything of code of FGD DAQ?
https://git.t2k.org/hastings/fgddaq/-/tree/master

Best regards,
Soichiro

We also use a Zynq chip and boot in the following order:

1. SD Card
   a. First Stage Bootloader
   b. PL Firmware
   c. UBOOT
2. NFS over Ethernet
   a. Linux kernel
   b. RootFS
   c. Mounting home directories


If you need details I can bring you in contact with the person who actually implemented that.

Best,
Stefan

Dear Stefan,

Thank you very much for your help.

I have already contacted someone who has used ZYNQ in that order and It's working fine for now.
But, I'll let you know if something goes wrong.

Best regards,
Soichiro 

A few months ago, definitions of SYNC and ASYNC in midas.h have been changed away from "0" and "1", 
and this caused problems with some event buffer management functions bm_xxx().

For example, when event buffers are getting full, bm_send_event(SYNC) unexpectedly started returning 
BM_ASYNC_RETURN instead of waiting for free space, causing unexpected crashes of frontend programs.

Part of the problem was confusion between SYNC/ASYNC used by buffer management (bm_xxx) and by run 
transition (cm_transition()) functions. Adding to confusion, documentation of bm_send_event() & co used 
FALSE/TRUE while most actual calls used SYNC/ASYNC.

To sort this out, an executive decision was made to abolish the SYNC/ASYNC defines:

For buffer management calls bm_send_event(), bm_receive_event(), etc, please use:
SYNC -> BM_WAIT
ASYNC -> BM_NO_WAIT

For run transitions, please use:
SYNC -> TR_SYNC
ASYNC -> TR_ASYNC
MTHREAD -> TR_MTHREAD
DETACH -> TR_DETACH

K.O.

• write a custom parser in C++ using the instructions contained in the Mhformat page;
  
• call the mhist program from within my application;
  
• call the mhdump program from within my application;
  

<p>[quote=&quot;Pintaudi Giorgio&quot;]Dear MIDAS people, I need to borrow your 
wisdom for a bit. I am developing a piece of software that should read the history data 
stored in a [FONT=Times New Roman].midas[/FONT] file (MIDAS format) and integrate it 
into the WAGASCI data quality output. In other words, I need to read some temperature 
values stored in a [FONT=Times New Roman].midas[/FONT] file and compare them with 
the MPPC gains and check for temperature/gain dependence. I see three possibilities: 
[LIST] [*] write a custom parser in C++ using the instructions contained in the 
[URL=https://midas.triumf.ca/MidasWiki/index.php/Mhformat]Mhformat page[/URL]; [*] call 
the mhist program from within my application; [*] call the mhdump program from within my 
application; [/LIST] [B]Which solution do you think is the best?[/B] Because there is no 
need for raw performance, if possible, I would like to write my application in Python3 but 
C++ is also an option. [/quote]</p>

(Please write messages in plain text format, thank you)

The format of .hst midas history files is pretty simple and mhdump.cxx is an easy to read 
illustration on how to read it from basic principles (without going through the midas library, 
which can be somewhat complicated). The newer "FILE" format for history is even simpler 
to read because it is just fixed-record-size binary data prepended by a text header.

You can also use the mh2sql program to import history data into an sql database (mysql 
and sqlite should work) or to convert .hst files to "FILE" format files. This works well
for "archiving" history data, because the "FILE" format works better for looking at old data,
and for looking at data in "months" or "years" timescale.

Back to your question, you can certainly use "mhdump" as is, using a pipe (popen()), or 
you can package mhdump.cxx as a c++ class and use it in your application. If you go this 
route, your contribution of such a c++ class back to midas would be very welcome.

You can also use mhist, but the mhist code cannot be trivially packaged as a c++ class
to use in your application.

You can also suggest that we write an easier to use history utility, we are always open to 
suggested improvements.

Let us know how it works out for you. Good luck!

K.O.

> The format of .hst midas history files is pretty simple and mhdump.cxx is an easy to read 
> illustration on how to read it from basic principles (without going through the midas library, 
> which can be somewhat complicated). The newer "FILE" format for history is even simpler 
> to read because it is just fixed-record-size binary data prepended by a text header.
> 
> You can also use the mh2sql program to import history data into an sql database (mysql 
> and sqlite should work) or to convert .hst files to "FILE" format files. This works well
> for "archiving" history data, because the "FILE" format works better for looking at old data,
> and for looking at data in "months" or "years" timescale.
> 
> Back to your question, you can certainly use "mhdump" as is, using a pipe (popen()), or 
> you can package mhdump.cxx as a c++ class and use it in your application. If you go this 
> route, your contribution of such a c++ class back to midas would be very welcome.
> 
> You can also use mhist, but the mhist code cannot be trivially packaged as a c++ class
> to use in your application.
> 
> You can also suggest that we write an easier to use history utility, we are always open to 
> suggested improvements.
> 
> Let us know how it works out for you. Good luck!
> 
> K.O.

Dear Konstantin,
thank you very much for the wealth of information you provided.
I have thought about it and I see two options:

- One is to convert to SQL format and then use a SQLite library to import the data in my 
application.

- The other is to encapsulate the mhdump.cxx code into a C++ class, as you say.

I am leaning towards the first option for three reasons.
1. I have never used a SQLite database so it is a good learning opportunity for me.
2, The SQLite database format is very well known and widespread, so there are tons of tools to 
handle it
3. I have taken a look at the mhdump.cxx source code and I think it is a beautiful piece of code, 
but has a very "functional" taste with little encapsulation. Basically, all the fun is happening 
inside the readHstFile function and there is no trivial way to get the data out of it. I don't mean 
that it would be difficult to wrap it around a C++ class, but I feel that I can learn more by going 
the SQL way.

PS some time ago, I don't remember if you or Stefan, recommended CLion as C++ IDE. I have tried it 
(together with PyCharm) and I must admit that it is really good. It took me years to configure Emacs 
as a IDE, while it took me minutes to have much better results in CLion. Thank you very much for 
your recommendation.

>
> - One is to convert to SQL format and then use a SQLite library to import the data in my 
> application.
> 

You can also configure midas to write history directly to an SQLITE database. I have not used
it recently, but it should still work. In terms of efficiency, sqlite file size is about the same
as .hst files. sqlite file and table naming is similar to the SQL and FILE implementation.

(But note that back when I implemented the SQLITE history writer, sqlite database corruption
recovery instructions were "delete the file, restore from backup". And indeed in every test
experiment I tried, the sqlite history databases eventually corrupted themselves. You see
same thing with google-chrome, lots of sqlite errors (bad locking, corrupted table, etc)
in it's terminal output).

>
> - The other is to encapsulate the mhdump.cxx code into a C++ class, as you say.
> 

If I were to write this today, there would be a c++ class that takes a history file,
iterates over all records and calls "callback" classlets. You can see this in the history.h
(HistoryBufferInterface) and in the tmfe.h (RpcHandlerInterface, etc).

I think this style of OO programming originally comes from java. If you so desire,
an "mhdump" class could be a nice way to learn it.

> 
> PS some time ago, I don't remember if you or Stefan, recommended CLion as C++ IDE. I have tried it 
> (together with PyCharm) and I must admit that it is really good. It took me years to configure Emacs 
> as a IDE, while it took me minutes to have much better results in CLion. Thank you very much for 
> your recommendation.
>

I remember, years ago, the Borland TurboC IDE was like a gift from Gods. But today, I think IDEs have
declined in quality and usefulness. They clog the screen with too much eye candy and fluff, use hard
to read fonts and silly colours, insist on using tabs where I want spaces, reformat the text even as I type it,
and detract from productive work with distracting popups ("try this new function!", "let's upgrade now!").

For serious programming, I use emacs with minimal decorations. I can easily open 3 or 4 windows at the same
time and still have enough screen space left for a terminal to run "make". And it is the only editor that can
edit the same file in two or more windows at the same time. You do not know you need this until
you work on odb.cxx.

K.O.

> PS some time ago, I don't remember if you or Stefan, recommended CLion as C++ IDE. I have tried it 
> (together with PyCharm) and I must admit that it is really good. It took me years to configure Emacs 
> as a IDE, while it took me minutes to have much better results in CLion. Thank you very much for 
> your recommendation.

Was probably me. I use it as my standard IDE and am quite happy with it. All the things KO likes with emacs, plus much 
more. Especially the CMake integration is nice, since you don't have to leave the IDE for editing, compiling and debugging. 
The tooltips the IDE gave me in the past months made me write code much better. So quite an opposite opinion compared 
with KO, but luckily this planet has space for all kinds of opinions. I made myself the cheat sheet attached, which lets me 
do things much faster. Maybe you can use it.

Stefan

> (But note that back when I implemented the SQLITE history writer, sqlite database corruption
> recovery instructions were "delete the file, restore from backup". And indeed in every test
> experiment I tried, the sqlite history databases eventually corrupted themselves. You see
> same thing with google-chrome, lots of sqlite errors (bad locking, corrupted table, etc)
> in it's terminal output).

Thank you for the info. But I do not quite understand the comment above.
Do you mean that there is something wrong with the SQLite library itself or with the way that MIDAS creates the SQLite 
database?

Eventually, I have settled for the SQLite format.
I could convert the MIDAS history files .hst to SQLite
database .sqlite3 using the utility mh2sql.
It worked out nicely, thank you for the advice.

However, as Konstantine predicted I did notice some
database corruption when a couple of problematic .hst
files were read. I solved the issue by just deleting
those .hst files (I think they were empty anyway).

Now I am developing a piece of code to read the
database using the SOCI library and integrate it
into a TTree but this is not relevant for MIDAS I think.

Thank you again for the discussion.

I recently needed to watch the Midas messages for a particular error - and 
thus needed a command to "get all the messages since a time t".

The documentation (https://midas.triumf.ca/MidasWiki/index.php/AJAX#jmsg) 
documents a way to "get the most recent n messages" - but when I dug into the 
code, I was delighted to find that the existing Midas code also supports the 
"get all messages since t" query.

For the "get all messages since t" query, the parameter t should be the unix 
timestamp in seconds, and the parameter n should be zero: curl -X GET 
"http://localhost:8081/?cmd=jmsg&n=0&t=1473437918".

Pretty useful!  Perhaps this should be added to the AJAX documentation?

> I recently needed to watch the Midas messages for a particular error - and 
> thus needed a command to "get all the messages since a time t".
> 
> The documentation (https://midas.triumf.ca/MidasWiki/index.php/AJAX#jmsg) 
> documents a way to "get the most recent n messages" - but when I dug into the 
> code, I was delighted to find that the existing Midas code also supports the 
> "get all messages since t" query.
> 
> For the "get all messages since t" query, the parameter t should be the unix 
> timestamp in seconds, and the parameter n should be zero: curl -X GET 
> "http://localhost:8081/?cmd=jmsg&n=0&t=1473437918".
> 
> Pretty useful!  Perhaps this should be added to the AJAX documentation?

Thank you - I have added it to the documentation.