#134 ipc_alloc errors when trying to have DSPSR run on a DADABuffer

[Emmanuel Fonseca]

Hello,

I've been trying to use the latest versions of PSRDADA and DSPSR for our setup at the CHIME telescope. Both were compiled following the nominal instructions, and linking to the CUDA-13.1 installation of our latest/test NVIDIA GPU seems successful when running make check. I'm happy to pass along logistical info if you would find it helpful.

When running "make check", the results indicate all tests pass. However, when I look at the log for OutputDADABufferTest, I see the folllowing:

[==========] Running 3 tests from 1 test suite.
[----------] Global test environment set-up.
[----------] 3 tests from OutputDADABufferTest
[ RUN      ] OutputDADABufferTest.test_create_destroy
ipc_alloc: shmget (key=a001, size=528, flag=1b6) No such file or directory
ipcsync_get: ipc_alloc error
ipcbuf_connect: ipcsync_get error
[2026-03-23-20:18:26] ERR: Failed to connect to Header Block

It seems likely that the underlying DADA and/or DSPSR utilities are not estimating the size value correctly. This idea is somewhat substantiated when following the tutorial outlined here, where the dspsr call produces an apparent "file not recognized" error but actually produces the same shmget error when running dspsr -V.

Again, please do let me know if you'd like any info from me.

Cheers,

• e.f.

[Emmanuel Fonseca]

As a follow-up, I've been trying different things and have a likely related view of the above issue. I tried out the following lines to load test data into a PSRDADA ring buffer and then execute dspsr:

dada_db -b 33554432 -n 16
dada_example_writer header.txt
dada_diskdb -f 1644-4559.dada &

(Using the commands given in the dspsr-DADA tutorial linked above did not work; I can indeed retrieve the header data when running the above and then executing dada_header -v.) When running dspsr, I see the following:

opening dada.info
dsp::SourceFactory::create filename='dada.info
dsp::File::create filename='dada.info
dsp::File::create with 7 registered sub-classes
dsp::File::create testing Dummy
dsp::DummyFile::is_valid first line != DUMMY
dsp::File::create testing DADABlock
dsp::DADABlockFile::is_valid fread (nbyte=4096)
dsp::File::create testing DADA
dsp::DADAFile::is_valid fread (nbyte=4096)
dsp::File::create testing CPSR2
CPSR2File::get_header - failed read: Successdsp::File::create testing DADABuffer
dsp::File::create DADABuffer::is_valid() returned true
dsp::Input ctor this=0x5cd0ab6a1ff0
dsp::File::open filename=dada.info
dsp::DADABuffer::close start
dsp::DADABuffer::open_file
dsp::DADABuffer::open_file key=dada passive=1
dsp::DADABuffer::reopen start
dsp::DADABuffer::load_header calling dada_hdu_open
dsp::DADABuffer::load_header size=4096 content=
HDR_SIZE     4096                   

END OF HEADER
ASCIIObservation::load required keywords:
  TELESCOPE
  SOURCE
  FREQ
  BW
  NPOL
  NBIT
  TSAMP
  UTC_START
  OBS_OFFSET
ASCIIObservation: failed read HDR_VERSION
dsp::File::create failed while testing DADABuffer

it looks like dspsr is able to recognize the input-file format and obtain shm-related data needed to instantiate some of the DADA-related routines, but is nonetheless not able to retrieve header data (whereas dada_header can output header data fine).

[Willem van Straten]

Hi Emmanuel,

I need to have a closer look at the first error that you reported, but the clue to the second error is

ASCIIObservation: failed read HDR_VERSION

It appears that your ASCII header contains only the text

HDR_SIZE     4096

Does this sound correct to you? DSPSR is expecting

HDR_VERSION 1.0

and the required keywords listed above:

ASCIIObservation::load required keywords:
  TELESCOPE
  SOURCE
  FREQ
  BW
  NPOL
  NBIT
  TSAMP
  UTC_START
  OBS_OFFSET

... hope this helps!

[Emmanuel Fonseca]

Hi @straten,

Thanks so much for your prompt response! For clarity, I'm basically running dspsr in the same way suggested in this tutorial, i.e., by supplying a key file to dspsr after having run the dada_ utilities described above so that dspsr can process data stored in a ring buffer; the specific dspsr command I use is:

dspsr -F 128:D -E 1644-4559.eph -P 1644-4559.polyco dada.info -V

So I'm not supplying the 1644-4559.dada test file directly to dspsr, but instead (trying to) load the data into a DADA-formated buffer and supplying a key file to dspsr. I still get the above error despite having a .hdr file, containing the header data below, in the same subdirectory containing the test data.

Key file (dada.info):

DADA INFO:
key dada
viewer

Header file (dada.hdr):

HDR_VERSION  1.0
HDR_SIZE     4096

TELESCOPE    PKS                    # telescope name
PRIMARY      cpsr1                  # primary node host name

# time of the rising edge of the first time sample
UTC_START    2007-05-18-15:55:58    # yyyy-mm-dd-hh:mm:ss.fs
MJD_START    54238.6638657407407    # MJD equivalent to the start UTC

OFFSET       5368709120             # bytes offset from the start MJD/UTC

SOURCE       J1644-4559             # name of the astronomical source
RA           16:44:49.28            # Right Ascension of the source
DEC          -45:59:09.5            # Declination of the source

FREQ         1405.000000            # centre frequency on sky in MHz
BW           -64                    # bandwidth of in MHz (-ve lower sb)
TSAMP        0.00781250             # sampling interval in microseconds

NBIT         2                      # number of bits per sample
NDIM         1                      # dimension of samples (2=complex, 1=real)
NPOL         2                      # number of polarizations observed

EDGE         0                      
LEVEL        300                    
CALFREQ      11.123000              
MODE         SURVEY                 
NMBYTES      5120                   
BUFFERSIZE   33554432               
HALT         0                      
OBS_OFFSET   0                      
INSTRUMENT   CPSR2                  
FILE_SIZE    536870912

[Willem van Straten]

Hi Emmanuel, thank you for this additional information. I could reproduce the error on my end (tutorial failure) and have just checked in some fixes to psrdada: the psrdada library has been evolving and at some point it stopped understanding the old CPSR2 data files. This backward compatibility has been restored.

Could you please git pull the latest version of psrdada and compile and install it? You might also need to recompile dspsr and install it again too.