question: parser for large binary file

[lermert]

Dear all,
this may be a very silly question, but since the specfem version I used a few years back, the format of the "large binary file" output seems to have changed. Is there a parser for the large binary files written by main, or a specification of the format? (regarding files all_seismograms__main.bin)

thanks in advance
Laura

[danielpeter]

hi Laura,

do you refer to these settings in the Par_file?

# save all seismograms in one large combined file instead of one file per seismogram
# to avoid overloading shared non-local file systems such as LUSTRE or GPFS for instance
SAVE_ALL_SEISMOS_IN_ONE_FILE    = .false.
USE_BINARY_FOR_LARGE_FILE       = .false.

this format hasn't changed for a while (10+ years?). however, the extract tool in utils/small_utilities/extract_all_seismos_from_large_file.f90 looks outdated. the seismogram names are now 512-characters long (and values are CUSTOM_REAL which by default is still the same as real). i'll update that.

the binary file format follows:

seismogram1_trace_name1 (fix 512 characters long, and names like "HT.LIT.MXE.sem")
t1 val1
..
tN valN
seismogram1_trace_name2 (like "HT.LIT.MXN.sem")
t1 val1
..
seismogram1_trace_name3 (like "HT.LIT.MXZ.sem")
t1 val1
..
seismogram2_trace_name1 (like "GE.ZKR.MXE.sem")
t1 val1
..

for N time steps.

ideally, having NTSTEP_BETWEEN_OUTPUT_SEISMOS = .. set such that it only outputs to the file at the very end of the simulation, makes it easier to read. otherwise, it will keep appending chunks of the seismos, thus repeating this format until it reaches the end.

note that since this is binary output, this can change depending on the system and compilers used. for a more independent storage format, you could consider using ASDF (option OUTPUT_SEISMOS_ASDF) or HDF5 (option OUTPUT_SEISMOS_HDF5) which would allow to browse through the files using corresponding tools.