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Writting Midas Events via FPGAs

The rb_xxx function are (thoroughly tested!) robust against high data rate given that you use them as intended:

1) Once you create the ring buffer via rb_create(), specify the maximum event size (overall event size, not bank size!). Later there is no protection any more, so if you obtain pdata from rb_get_wp, you can of course write 4GB to pdata, overwriting everything in your memory, causing a total crash. It's your responsibility to not write more bytes into pdata then 
what you specified as max event size in rb_create()

2) Once you obtain a write pointer to the ring buffer via rb_get_wp, this function might fail when the receiving side reads data slower than the producing side, simply because the buffer is full. In that case the producing side has to wait until space is freed up in the buffer by the receiving side. If your call to rb_get_wp returns DB_TIMEOUT, it means that the 
function did not obtain enough free space for the next event. In that case you have to wait (like ss_sleep(10)) and try again, until you succeed. Only when rb_get_wp() returns DB_SUCCESS, you are allowed to write into pdata, up to the maximum event size specified in rb_create of course. I don't see this behaviour in your code. You would need something 
like

do {
   status = rb_get_wp(rbh, (void **)&pdata, 10);
   if (status == DB_TIMEOUT)
      ss_sleep(10);
   } while (status == DB_TIMEOUT);

Best,
Stefan


> Dear all,
> 
> we creating Midas events directly inside a FPGA and send them off via DMA into the PC RAM. For reading out this RAM via Midas the FPGA sends as a pointer where it has written the last 4kB of data. We use this pointer for telling the ring buffer of midas where the new events are. The buffer looks something like:
> 
> // event 1
> dma_buf[0] = 0x00000001; // Trigger and Event ID
> dma_buf[1] = 0x00000001; // Serial number
> dma_buf[2] = TIME; // time
> dma_buf[3] = 18*4-4*4; // event size
> dma_buf[4] = 18*4-6*4; // all bank size
> dma_buf[5] = 0x11; // flags
> // bank 0
> dma_buf[6] = 0x46454230; // bank name
> dma_buf[7] = 0x6; // bank type TID_DWORD
> dma_buf[8] = 0x3*4; // data size
> dma_buf[9] = 0xAFFEAFFE; // data
> dma_buf[10] = 0xAFFEAFFE; // data
> dma_buf[11] = 0xAFFEAFFE; // data
> // bank 1
> dma_buf[12] = 0x1; // bank name
> dma_buf[12] = 0x46454231; // bank name
> dma_buf[13] = 0x6; // bank type TID_DWORD
> dma_buf[14] = 0x3*4; // data size
> dma_buf[15] = 0xAFFEAFFE; // data
> dma_buf[16] = 0xAFFEAFFE; // data
> dma_buf[17] = 0xAFFEAFFE; // data
> 
> // event 2
> .....
> 
> dma_buf[fpga_pointer] = 0xXXXXXXXX;
> 
> 
> And we do something like:
> 
> while{true}
>    // obtain buffer space
>    status = rb_get_wp(rbh, (void **)&pdata, 10);
>    fpga_pointer = fpga.read_last_data_add();
> 
>    wlen = last_fpga_pointer - fpga_pointer; \\ in 32 bit words
>    copy_n(&dma_buf[last_fpga_pointer], wlen, pdata);
>    rb_status = rb_increment_wp(rbh, wlen * 4); \\ in byte
> 
>    last_fpga_pointer = fpga_pointer;
> 
> Leaving the case out where the dma_buf wrap around this works fine for a small data rate. But if we increase the rate the fpga_pointer also increases really fast and wlen gets quite big. Actually it gets bigger then max_event_size which is checked in rb_increment_wp leading to an error. 
> 
> The problem now is that the event size is actually not to big but since we have multi events in the buffer which are read by midas in one step. So we think in this case the function rb_increment_wp is comparing actually the wrong thing. Also increasing the max_event_size does not help.
> 
> Remark: dma_buf is volatile so memcpy is not possible here.
> 
> Cheers,
> Marius

Writting Midas Events via FPGAs

The rb_xxx functions are (thoroughly tested) robust against high data rate given that you use them as intended:

1) Once you create the ring buffer via rb_create(), specify the maximum event size (midas event, not bank size!). Later there is not protection any more, so if you obtain pdata from rb_get_wp, you can of course write 4GB to pdata, overwriting everything in your memory, causing a fatal crash. It's your duty not to write more bytes into pdata then what you specified in rb_create()

2) Once you obtain a write pointer to the ring buffer via rb_get_wp(), this function might fail when the receiving side reads data slower than the producing side, simply because the buffer is full. In that case the producing side was to wait to get new buffer space. If you call to rb_get_wp() returns DB_TIMEOUT, it means that the function did not obtain enough free space for the next event. In that case you have to wait (like ss_sleep(10)) and try again. Only when rb_get_wp() returns DB_SUCCESS, you are allowed to write into pdata (up to the maximum event size specified in rb_create() of course).

/Stefan


> Dear all,
> 
> we creating Midas events directly inside a FPGA and send them off via DMA into the PC RAM. For reading out this RAM via Midas the FPGA sends as a pointer where it has written the last 4kB of data. We use this pointer for telling the ring buffer of midas where the new events are. The buffer looks something like:
> 
> // event 1
> dma_buf[0] = 0x00000001; // Trigger and Event ID
> dma_buf[1] = 0x00000001; // Serial number
> dma_buf[2] = TIME; // time
> dma_buf[3] = 18*4-4*4; // event size
> dma_buf[4] = 18*4-6*4; // all bank size
> dma_buf[5] = 0x11; // flags
> // bank 0
> dma_buf[6] = 0x46454230; // bank name
> dma_buf[7] = 0x6; // bank type TID_DWORD
> dma_buf[8] = 0x3*4; // data size
> dma_buf[9] = 0xAFFEAFFE; // data
> dma_buf[10] = 0xAFFEAFFE; // data
> dma_buf[11] = 0xAFFEAFFE; // data
> // bank 1
> dma_buf[12] = 0x1; // bank name
> dma_buf[12] = 0x46454231; // bank name
> dma_buf[13] = 0x6; // bank type TID_DWORD
> dma_buf[14] = 0x3*4; // data size
> dma_buf[15] = 0xAFFEAFFE; // data
> dma_buf[16] = 0xAFFEAFFE; // data
> dma_buf[17] = 0xAFFEAFFE; // data
> 
> // event 2
> .....
> 
> dma_buf[fpga_pointer] = 0xXXXXXXXX;
> 
> 
> And we do something like:
> 
> while{true}
>    // obtain buffer space
>    status = rb_get_wp(rbh, (void **)&pdata, 10);
>    fpga_pointer = fpga.read_last_data_add();
> 
>    wlen = last_fpga_pointer - fpga_pointer; \\ in 32 bit words
>    copy_n(&dma_buf[last_fpga_pointer], wlen, pdata);
>    rb_status = rb_increment_wp(rbh, wlen * 4); \\ in byte
> 
>    last_fpga_pointer = fpga_pointer;
> 
> Leaving the case out where the dma_buf wrap around this works fine for a small data rate. But if we increase the rate the fpga_pointer also increases really fast and wlen gets quite big. Actually it gets bigger then max_event_size which is checked in rb_increment_wp leading to an error. 
> 
> The problem now is that the event size is actually not to big but since we have multi events in the buffer which are read by midas in one step. So we think in this case the function rb_increment_wp is comparing actually the wrong thing. Also increasing the max_event_size does not help.
> 
> Remark: dma_buf is volatile so memcpy is not possible here.
> 
> Cheers,
> Marius

Writting Midas Events via FPGAs

Dear all,

we creating Midas events directly inside a FPGA and send them off via DMA into the PC RAM. For reading out this RAM via Midas the FPGA sends as a pointer where it has written the last 4kB of data. We use this pointer for telling the ring buffer of midas where the new events are. The buffer looks something like:

// event 1
dma_buf[0] = 0x00000001; // Trigger and Event ID
dma_buf[1] = 0x00000001; // Serial number
dma_buf[2] = TIME; // time
dma_buf[3] = 18*4-4*4; // event size
dma_buf[4] = 18*4-6*4; // all bank size
dma_buf[5] = 0x11; // flags
// bank 0
dma_buf[6] = 0x46454230; // bank name
dma_buf[7] = 0x6; // bank type TID_DWORD
dma_buf[8] = 0x3*4; // data size
dma_buf[9] = 0xAFFEAFFE; // data
dma_buf[10] = 0xAFFEAFFE; // data
dma_buf[11] = 0xAFFEAFFE; // data
// bank 1
dma_buf[12] = 0x1; // bank name
dma_buf[12] = 0x46454231; // bank name
dma_buf[13] = 0x6; // bank type TID_DWORD
dma_buf[14] = 0x3*4; // data size
dma_buf[15] = 0xAFFEAFFE; // data
dma_buf[16] = 0xAFFEAFFE; // data
dma_buf[17] = 0xAFFEAFFE; // data

// event 2
.....

dma_buf[fpga_pointer] = 0xXXXXXXXX;


And we do something like:

while{true}
   // obtain buffer space
   status = rb_get_wp(rbh, (void **)&pdata, 10);
   fpga_pointer = fpga.read_last_data_add();

   wlen = last_fpga_pointer - fpga_pointer; \\ in 32 bit words
   copy_n(&dma_buf[last_fpga_pointer], wlen, pdata);
   rb_status = rb_increment_wp(rbh, wlen * 4); \\ in byte

   last_fpga_pointer = fpga_pointer;

Leaving the case out where the dma_buf wrap around this works fine for a small data rate. But if we increase the rate the fpga_pointer also increases really fast and wlen gets quite big. Actually it gets bigger then max_event_size which is checked in rb_increment_wp leading to an error. 

The problem now is that the event size is actually not to big but since we have multi events in the buffer which are read by midas in one step. So we think in this case the function rb_increment_wp is comparing actually the wrong thing. Also increasing the max_event_size does not help.

Remark: dma_buf is volatile so memcpy is not possible here.

Cheers,
Marius

Compiling Midas in OS 10.15 Catalina

Now you are stuck with openssl, which is optional for mhttpd. If you only use mhttpd locally, you maybe don't need SSL support. In that case you can jus do

[midas/build] $ cmake -D NO_SSL=1 ..

To disable that. If you do need SSL, maybe you can try to install openssl11 via mac ports.

Stefan

Compiling Midas in OS 10.15 Catalina

> Another thought: Can you delete the midas build directory and run cmake again? Like
> 
> $ cd midas/build
> $ rm -rf *
> $ cmake ..
> $ make VERBOSE=1
> 
> If you have the old build cache and upgraded your OS in meantime, the cache needs to be rebuild. The VERBOSE 
> flag tells you the compiler options, and you see where the compiler looks for the SDK directory.
> 
> Cheers,
> Stefan

Hi Stefan, 

Thanks again for your reply. Yes! the suggestion of rebuilding the cache was the right one, this is the output of cmake ..

Darrens-Mac-mini:~ betacage$ cd packages/midas/build/
Darrens-Mac-mini:build betacage$ rm -rf *
Darrens-Mac-mini:build betacage$ cmake ..
-- MIDAS: cmake version: 3.16.3
-- The C compiler identification is AppleClang 11.0.0.11000033
-- The CXX compiler identification is AppleClang 11.0.0.11000033
-- Check for working C compiler: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/cc
-- Check for working C compiler: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/cc -- works
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Detecting C compile features
-- Detecting C compile features - done
-- Check for working CXX compiler: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/c++
-- Check for working CXX compiler: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/c++ -- works
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- MIDAS: CMAKE_INSTALL_PREFIX: /Users/betacage/packages/midas
-- MIDAS: Found ROOT version 6.18/04
-- Found ZLIB: /usr/lib/libz.dylib (found version "1.2.11") 
-- MIDAS: Found ZLIB version 1.2.11
-- Found OpenSSL: /usr/lib/libcrypto.dylib (found version "1.1.1d")  
-- MIDAS: Found OpenSSL version 1.1.1d
-- MIDAS: MySQL not found
-- MIDAS: ODBC not found
-- MIDAS: SQLITE not found
-- MIDAS: nvidia-smi not found
-- Setting default build type to "RelWithDebInfo"
-- Found Git: /usr/bin/git (found version "2.21.1 (Apple Git-122.3)") 
-- MIDAS example/experiment: MIDAS in-tree-build
-- MIDAS: Found ZLIB version 1.2.11
-- MIDAS example/experiment: Found ROOT version 6.18/04
-- Configuring done
-- Generating done
-- Build files have been written to: /Users/betacage/packages/midas/build


Unfortunately running make VERBOSE=1 the compilation crashes, with the following error 

[ 39%] Linking CXX executable mhttpd
cd /Users/betacage/packages/midas/build/progs && /Applications/CMake.app/Contents/bin/cmake -E cmake_link_script CMakeFiles/mhttpd.dir/link.txt 
--verbose=1
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/c++  -O2 -g -DNDEBUG -isysroot 
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.15.sdk -Wl,-search_paths_first -Wl,-
headerpad_max_install_names  CMakeFiles/mhttpd.dir/mhttpd.cxx.o CMakeFiles/mhttpd.dir/mongoose6.cxx.o CMakeFiles/mhttpd.dir/mgd.cxx.o 
CMakeFiles/mhttpd.dir/__/mscb/src/mscb.cxx.o  -o mhttpd  ../libmidas.a /usr/lib/libssl.dylib /usr/lib/libcrypto.dylib -lz 
ld: cannot link directly with dylib/framework, your binary is not an allowed client of /usr/lib/libcrypto.dylib for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
make[2]: *** [progs/mhttpd] Error 1
make[1]: *** [progs/CMakeFiles/mhttpd.dir/all] Error 2
make: *** [all] Error 2


Libcrypto seems to be part of the OpenSSL, so I am back to the original problem again. I did install OpenSSL via MacPorts. 

I have found this tread regarding this problem. But have to go and pick up my kids from school, so I don't have time to investigate today.
https://stackoverflow.com/questions/58446253/xcode-11-ld-error-your-binary-is-not-an-allowed-client-of-usr-lib-libcrypto-dy

Thanks again for staying with me and for responding so promptly. 

Berta

Compiling Midas in OS 10.15 Catalina

Another thought: Can you delete the midas build directory and run cmake again? Like

$ cd midas/build
$ rm -rf *
$ cmake ..
$ make VERBOSE=1

If you have the old build cache and upgraded your OS in meantime, the cache needs to be rebuild. The VERBOSE 
flag tells you the compiler options, and you see where the compiler looks for the SDK directory.

Cheers,
Stefan

Compiling Midas in OS 10.15 Catalina

Another thought: Can you delete the build directory and run cmake again? Like

$ cd /midas/build
$ rm -rf *
$ cmake ..

If you have the old build cache and upgraded the OS in meantime, the cache needs to be rebuild.

Stefan

Compiling Midas in OS 10.15 Catalina

> For your reference, here on my MacOSX 10.14.6 with XCode 11.3.1 the pthread.h file is present in locations listed below.
> 
> Did you execute "xcode-select --install" ?
> 
> 
> ~$ locate pthread.h
> /Applications/Xcode.app/Contents/Developer/Platforms/AppleTVOS.platform/Developer/SDKs/AppleTVOS.sdk/usr/include/pthread/pthread.h
> /Applications/Xcode.app/Contents/Developer/Platforms/AppleTVOS.platform/Developer/SDKs/AppleTVOS.sdk/usr/include/pthread.h
> /Applications/Xcode.app/Contents/Developer/Platforms/AppleTVSimulator.platform/Developer/SDKs/AppleTVSimulator.sdk/usr/include/pthread/pthread.h
> /Applications/Xcode.app/Contents/Developer/Platforms/AppleTVSimulator.platform/Developer/SDKs/AppleTVSimulator.sdk/usr/include/pthread.h
> /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/usr/include/pthread/pthread.h
> /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/usr/include/pthread.h
> /Applications/Xcode.app/Contents/Developer/Platforms/WatchOS.platform/Developer/SDKs/WatchOS.sdk/usr/include/pthread/pthread.h
> /Applications/Xcode.app/Contents/Developer/Platforms/WatchOS.platform/Developer/SDKs/WatchOS.sdk/usr/include/pthread.h
> /Applications/Xcode.app/Contents/Developer/Platforms/WatchSimulator.platform/Developer/SDKs/WatchSimulator.sdk/usr/include/pthread/pthread.h
> /Applications/Xcode.app/Contents/Developer/Platforms/WatchSimulator.platform/Developer/SDKs/WatchSimulator.sdk/usr/include/pthread.h
> /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS.sdk/usr/include/pthread/pthread.h
> /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS.sdk/usr/include/pthread.h
> /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator.sdk/usr/include/pthread/pthread.h
> /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator.sdk/usr/include/pthread.h
> /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/pthread/pthread.h
> /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/pthread.h

Hi Stefan,

Thanks for looking into this. Yes, I have done  "xcode-select --install"

This is my output when I try to locate pthread.h

Darrens-Mac-mini:~ betacage$ locate pthread.h
/Applications/Xcode.app/Contents/Developer/Platforms/AppleTVOS.platform/Developer/SDKs/AppleTVOS.sdk/usr/include/pthread/pthread.h
/Applications/Xcode.app/Contents/Developer/Platforms/AppleTVOS.platform/Developer/SDKs/AppleTVOS.sdk/usr/include/pthread.h
/Applications/Xcode.app/Contents/Developer/Platforms/AppleTVSimulator.platform/Developer/SDKs/AppleTVSimulator.sdk/usr/include/pthread/pthread.h
/Applications/Xcode.app/Contents/Developer/Platforms/AppleTVSimulator.platform/Developer/SDKs/AppleTVSimulator.sdk/usr/include/pthread.h
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/usr/include/pthread/pthread.h
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/usr/include/pthread.h
/Applications/Xcode.app/Contents/Developer/Platforms/WatchOS.platform/Developer/SDKs/WatchOS.sdk/usr/include/pthread/pthread.h
/Applications/Xcode.app/Contents/Developer/Platforms/WatchOS.platform/Developer/SDKs/WatchOS.sdk/usr/include/pthread.h
/Applications/Xcode.app/Contents/Developer/Platforms/WatchSimulator.platform/Developer/SDKs/WatchSimulator.sdk/usr/include/pthread/pthread.h
/Applications/Xcode.app/Contents/Developer/Platforms/WatchSimulator.platform/Developer/SDKs/WatchSimulator.sdk/usr/include/pthread.h
/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS.sdk/usr/include/pthread/pthread.h
/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS.sdk/usr/include/pthread.h
/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator.sdk/usr/include/pthread/pthread.h
/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator.sdk/usr/include/pthread.h
/Library/Developer/CommandLineTools/SDKs/MacOSX10.14.sdk/usr/include/pthread/pthread.h
/Library/Developer/CommandLineTools/SDKs/MacOSX10.14.sdk/usr/include/pthread.h
/Library/Developer/CommandLineTools/SDKs/MacOSX10.15.sdk/usr/include/pthread/pthread.h
/Library/Developer/CommandLineTools/SDKs/MacOSX10.15.sdk/usr/include/pthread.h

and this is what I see in my SDKs folder 

Darrens-Mac-mini:SDKs betacage$ pwd
/Library/Developer/CommandLineTools/SDKs
Darrens-Mac-mini:SDKs betacage$ ls
MacOSX.sdk	MacOSX10.14.sdk	MacOSX10.15.sdk

So it looks like in this computer one needs to read the version of the SDK as pthread.h is not in MacOSX.sdk but in MacOSX10.15.sdk

Thanks 

Berta

Difference between "Event Data Size" and "All Bank Size"

Thanks for pointing out this error. The "All Bank Size" contains the size of all banks including their 
bank headers, but NOT the global bank header itself. I modified the documentation accordingly.

If you want to study the C code which tells you how to fill these headers, look at midas.cxx line 
14788.

Best,
Stefan

> Dear all,
> 
> we are trying to build Midas events on FPGAs and send them directly to the midas
> ring buffer via copy_n. According to the wiki
> https://midas.triumf.ca/MidasWiki/index.php/Event_Structure Event Data Size is:
> "The event data size contains the size of the event in bytes excluding the
> header." and All Bank Size is: "Size in bytes of the following data plus the
> size of the bank header". So are they actually the same or what header is the
> header in the first sentence also the bank header?
> 
> Cheers,
> Marius
> 
>

Difference between "Event Data Size" and "All Bank Size"

Dear all,

we are trying to build Midas events on FPGAs and send them directly to the midas
ring buffer via copy_n. According to the wiki
https://midas.triumf.ca/MidasWiki/index.php/Event_Structure Event Data Size is:
"The event data size contains the size of the event in bytes excluding the
header." and All Bank Size is: "Size in bytes of the following data plus the
size of the bank header". So are they actually the same or what header is the
header in the first sentence also the bank header?

Cheers,
Marius

Force triggering of idle routine of a frontend

I had a look again at the issue. If you sett the event limit to zero in the EQUIPMENT list, then the idle() routine of your class driver is called as often as possible. Typically with 100 Hz. It's then up to you what to do in the class driver. The hv_idle() routine of the HV class driver shipped in the distribution for example read a channel more often if it has been changed recently. Look at the lines

/* additionally read channel recently updated if not multithreaded */
if (!(hv_info->driver[hv_info->last_channel]->flags & DF_MULTITHREAD)) {

act_time = ss_millitime();

act = (hv_info->last_channel_updated + 1) % hv_info->num_channels;
while (!(act_time - hv_info->last_change[act] < 10000)) {
act = (act + 1) % hv_info->num_channels;
if (act == hv_info->last_channel_updated) {
/* non found, so return */
return status;
}
}

/* updated channel found, so read it additionally */
status = hv_read(pequipment, act);
hv_info->last_channel_updated = act;
}

You can do similar things there like if you are ramping. On an end-of-run, the class drivers cd_xx_read() routine is called from the framework, which in turn sends a full midas event down the stream, but getting the current slow control values from its local cache, not from the actual device (otherwise stopping a run could be very slow). So if you want all values at the end of the run with good precision, you have to read them DURING the run as fast as possible. That's why I posted my comment about fixing dropped serial connections automatically and reading as fast as possible.

Stefan

Pintaudi Giorgio wrote:

Dear Stefan,
Thank you for the advice. I will try to modify the driver as you say. As for the dynamical change of readout rate, basically you are telling me that is not achievable without dirty hacks like mine and it is better to find a way to avoid it.

Compiling Midas in OS 10.15 Catalina

For your reference, here on my MacOSX 10.14.6 with XCode 11.3.1 the pthread.h file is present in locations listed below.

Did you execute "xcode-select --install" ?


~$ locate pthread.h
/Applications/Xcode.app/Contents/Developer/Platforms/AppleTVOS.platform/Developer/SDKs/AppleTVOS.sdk/usr/include/pthread/pthread.h
/Applications/Xcode.app/Contents/Developer/Platforms/AppleTVOS.platform/Developer/SDKs/AppleTVOS.sdk/usr/include/pthread.h
/Applications/Xcode.app/Contents/Developer/Platforms/AppleTVSimulator.platform/Developer/SDKs/AppleTVSimulator.sdk/usr/include/pthread/pthread.h
/Applications/Xcode.app/Contents/Developer/Platforms/AppleTVSimulator.platform/Developer/SDKs/AppleTVSimulator.sdk/usr/include/pthread.h
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/usr/include/pthread/pthread.h
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/usr/include/pthread.h
/Applications/Xcode.app/Contents/Developer/Platforms/WatchOS.platform/Developer/SDKs/WatchOS.sdk/usr/include/pthread/pthread.h
/Applications/Xcode.app/Contents/Developer/Platforms/WatchOS.platform/Developer/SDKs/WatchOS.sdk/usr/include/pthread.h
/Applications/Xcode.app/Contents/Developer/Platforms/WatchSimulator.platform/Developer/SDKs/WatchSimulator.sdk/usr/include/pthread/pthread.h
/Applications/Xcode.app/Contents/Developer/Platforms/WatchSimulator.platform/Developer/SDKs/WatchSimulator.sdk/usr/include/pthread.h
/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS.sdk/usr/include/pthread/pthread.h
/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS.sdk/usr/include/pthread.h
/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator.sdk/usr/include/pthread/pthread.h
/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator.sdk/usr/include/pthread.h
/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/pthread/pthread.h
/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/pthread.h

switch midas to c++ threads?

> Hi, Stefan & co - now that midas is c++11 and c++11 comes with a threads library, should we 
> switch midas to use the c++11 threads instead of pthreads? (Of course on Linux c++11 
> threads are a layer on top of pthreads, the best I know).
> 
> This should remove the dependency on pthreads.h and use a more native implementation of 
> threads on MacOS and Windows. (again, the best I can tell).
> 
> Of course this depends on c++11 threads having all the functions we need. Specifically, "lock 
> with timeout" is useful to deal with "gah! everything stopped! what do I do!", a problem 
> bedeviling midas in the early days (and still happens today!). Current midas kills everything 
> after 5 minutes of deadlock - then the user knows how to restart everything and the developer 
> has core dumps to look at. (to see which program/thread holds the lock and would not give it 
> up).
> 
> Any thoughts on this?
> 
> K.O.

Hi, I just wanted to say that I have seen this post and maybe that is the solution to the pthreads compiler problem in OS 10.15, but 
of course I am a total amateur in here. Thanks for thinking about this and I will wait and hold to see what gets decided. Thanks

Berta

Compiling Midas in OS 10.15 Catalina

> > Any luck with Midas in OS 10.15? 
> 
> Best I can tell, the problem is not in midas: pthread.h should be there, somewhere.
> 
> K.O.


HI Konstain, 

Thanks for your reply. I have been investigating this issue of pthread in OS 10.15.  Found this forum post 
https://github.com/wjakob/nori/issues/16

that seem to suggest that pthread.h is in a different directory from OS 10.14 and on. And the end of the post the 
developer suggests that he has found a way to fix the Cmake to work so I have checked his code updates in here 
https://github.com/wjakob/nori/commit/be46cccc01a75b21dad1a3f61baa108fe644fc4b

I have added his lines 


if(APPLE)
   # Try to auto-detect a suitable SDK
   execute_process(COMMAND bash -c "xcodebuild -version -sdk | grep MacOSX | grep Path | head -n 1 | cut -f 2 -
d ' '" OUTPUT_VARIABLE CMAKE_OSX_SYSROOT)
   string(REGEX REPLACE "(\r?\n)+$" "" CMAKE_OSX_SYSROOT "${CMAKE_OSX_SYSROOT}")
   string(REGEX REPLACE "^.*X([0-9.]*).sdk$" "\\1" CMAKE_OSX_DEPLOYMENT_TARGET 
"${CMAKE_OSX_SYSROOT}")
 endif()

to my local pakages/midas/CMakeLists.txt and run cmake .., make install again but now I get a different error 

[  1%] Building CXX object CMakeFiles/mfeo.dir/src/mfe.cxx.o
clang: error: invalid version number in '-mmacosx-version-
min=/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/DriverKit19.0.sdk'
clang: warning: using sysroot for 'DriverKit' but targeting 'MacOSX' [-Wincompatible-sysroot]


I will continue investigating this issue tomorrow, but please let me know if you have any suggestions.

Also my version of cmake is 3.16.3

Thanks 

Berta

switch midas to c++ threads?

I'm thinking of this already since some time, and it was part of my motivation switching to C++11.
I was delighted to see that what we do in system.c (encapsulate system functions such as threads
and shared memory) is now done natively in C++11, and it's done by experts and not amateurs like us.

I see that with std::timed_mutex and try_lock_for we have the desired timeout function. Pity that
C++11 does not contain inter-process communication like semaphores, so there we still have to use
our old functions. 

But for threads switching to std::thread, I'm all in.

Stefan

> Hi, Stefan & co - now that midas is c++11 and c++11 comes with a threads library, should we 
> switch midas to use the c++11 threads instead of pthreads? (Of course on Linux c++11 
> threads are a layer on top of pthreads, the best I know).
> 
> This should remove the dependency on pthreads.h and use a more native implementation of 
> threads on MacOS and Windows. (again, the best I can tell).
> 
> Of course this depends on c++11 threads having all the functions we need. Specifically, "lock 
> with timeout" is useful to deal with "gah! everything stopped! what do I do!", a problem 
> bedeviling midas in the early days (and still happens today!). Current midas kills everything 
> after 5 minutes of deadlock - then the user knows how to restart everything and the developer 
> has core dumps to look at. (to see which program/thread holds the lock and would not give it 
> up).
> 
> Any thoughts on this?
> 
> K.O.

Force triggering of idle routine of a frontend

> We had a case where a detector produced electrostatic discharges which only lasted for a second or so
> and we were happy to detect this in spikes in the HV current. With measurements of only one per minute
> we would not have realized that so quicky.

For the T2K/ND280 TPC we implemented something similar. The TPC uses MicroMegas detector which sparks during 
normal operation. We asked Wiener/ISEG to implement a "spark counting mode" for us (and they did). In this mode,
high voltage over-current (a micromegas spark) sets a special flag (does not trip the high voltage). Our midas frontend
reads this flag at rate about 1/min, if flag is set, clears it, increments the software spark counter, reads the flag again,
if the flag is still set (failed to clear), it means this was not a normal spark but a high voltage breakdown
and the offending channel is shut down. I believe this mode is still part of the ISEG normal firmware.

Because the Wiener/ISEG interface uses SNMP to "read all data in one operation", the MIDAS "device driver" structure
was not useful, the readout was a simple loop, the readout frequency was easy to control, and indeed,
we read the high voltage with increased frequency during ramping. This was easy to implement because we
did not have to fight the MIDAS "device driver" framework.

If you want a similar solution, talk to the device, interpret the data, record values to odb and history, generate
midas events - all without hand holding from (arm wrestling with the rest of) midas - I recommend
the new tmfe.h/tmfe.cxx c++ frontend - see the two examples in midas/progs/fetest_tmfe.cxx
and fetest_tmfe_thread.cxx (single-threaded and multi-threaded).

K.O.

switch midas to c++ threads?

Hi, Stefan & co - now that midas is c++11 and c++11 comes with a threads library, should we 
switch midas to use the c++11 threads instead of pthreads? (Of course on Linux c++11 
threads are a layer on top of pthreads, the best I know).

This should remove the dependency on pthreads.h and use a more native implementation of 
threads on MacOS and Windows. (again, the best I can tell).

Of course this depends on c++11 threads having all the functions we need. Specifically, "lock 
with timeout" is useful to deal with "gah! everything stopped! what do I do!", a problem 
bedeviling midas in the early days (and still happens today!). Current midas kills everything 
after 5 minutes of deadlock - then the user knows how to restart everything and the developer 
has core dumps to look at. (to see which program/thread holds the lock and would not give it 
up).

Any thoughts on this?

K.O.

Compiling Midas in OS 10.15 Catalina

> Any luck with Midas in OS 10.15? 

Best I can tell, the problem is not in midas: pthread.h should be there, somewhere.

K.O.

Force triggering of idle routine of a frontend

You dirty hacks will probably work, but what you REALLY want is to read out your HV always as fast as possible, not only during run transitions or ramping. We had a case where a detector produced electrostatic discharges which only lasted for a second or so, and we were happy to detect this in spikes in the HV current. With measurements of only one per minute we would not have realized that so quicky.

Stefan

Pintaudi Giorgio wrote:

Force triggering of idle routine of a frontend

Stefan Ritt wrote:

Dear Giorgio,

ok, now I'm slowly getting your point.

Dynamically changing the slow control readout rate is possible with your modification, but I consider this badd practice.

You mentioned the case of your HV over a quirky serial line. I had the same some years ago. Rather than reducing the readout rate to reduce the number of errors, I modified my device driver. If the connection is broken, the driver tries silently to reconnect. Only if the reconnect fails for more than a given period (like 1 min), then an error is produced. Otherwise the driver reads as fast as possible. Imagine you have some instabilities in your HV, which only last for a few seconds. If you read only once per minute, you might miss that. We worked hard to make the slow control system multi-threaded, so a slow many-times-retrying-to-reconnect driver does not slow any other equipment. On the other hand, if the re-connect fails for a minute, then you know that your HV unit really has a problem the shifter should follow up.

Best,
Stefan

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