crash with multiple merge axis views

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I have the following code for a gpuspec pipeline:

import glob
from datetime import datetime
import time
from copy import deepcopy

import bifrost
import bifrost.pipeline as bfp
import bifrost.blocks as blocks
import bifrost.views as views
import bifrost.guppi_raw as guppi_raw
import bifrost.sigproc as sigproc
from bifrost.DataType import DataType

with bfp.Pipeline() as pipeline:

    n_int    = 128
    n_chunks = 1            # I want this to be 2, but I run out of GPU memory

    filelist = sorted(glob.glob('*.raw'))[:2]

    # Read from guppi raw file
    b_guppi   = blocks.read_guppi_raw(filelist, core=1, buffer_nframe=4)
    b_gup2    = views.rename_axis(b_guppi, 'freq', 'channel')

    # Buffer up two blocks & reshape to allow longer FFT
    b_gup2    = views.split_axis(b_gup2, axis='time', n=n_chunks, label='time_chunk')
    b_gup2    = blocks.transpose(b_gup2, axes=['time', 'channel', 'time_chunk', 'fine_time', 'pol'], buffer_nframe=1)
    b_gup2    = views.merge_axes(b_gup2, 'time_chunk', 'fine_time', label='fine_time')

    # Copy over to GPU and FFT
    b_copy    = blocks.copy(b_gup2,  space='cuda', buffer_nframe=1, core=1)
    b_fft     = blocks.fft(b_copy,  axes='fine_time', axis_labels='freq', buffer_nframe=1, core=2)
    b_ffs     = blocks.fftshift(b_fft, axes='freq', buffer_nframe=1, core=2)
    b_pow     = blocks.detect(b_ffs, mode='stokes', buffer_nframe=1, core=2)
    b_acc     = blocks.accumulate(b_pow, nframe=n_int, buffer_nframe=1, core=2)

    # Copy back to host and flatten channel/freq axis to form output spectra
    b_copp    = blocks.copy(b_acc, space='system', buffer_nframe=1, core=3)
    blocks.print_header(b_copp)

    b_flat    = views.merge_axes(b_copp, 'channel', 'freq', label='freq')
    #b_writer = write_to_disk_here()

    pipeline.run()

Which when run crashes:

dancpr@bldcpr:/bldata/pulsar_dev$ python bf_gpuspec_hires.py
Exception in thread Pipeline_0/CopyBlock_0:
Traceback (most recent call last):
  File "/usr/lib/python2.7/threading.py", line 801, in __bootstrap_inner
    self.run()
  File "/usr/lib/python2.7/threading.py", line 754, in run
    self.__target(*self.__args, **self.__kwargs)
  File "build/bdist.linux-x86_64/egg/bifrost/pipeline.py", line 293, in run
    self.main(active_orings)
  File "build/bdist.linux-x86_64/egg/bifrost/pipeline.py", line 426, in main
    self.sequence_proclogs[i].update(iseq.header)
  File "build/bdist.linux-x86_64/egg/bifrost/ring2.py", line 288, in header
    hdr = self.header_transform(deepcopy(hdr))
  File "build/bdist.linux-x86_64/egg/bifrost/views/basic_views.py", line 137, in header_transform
    axis2 = tensor['labels'].index(axis2)
ValueError: 'freq' is not in list

Catching the ValueError and adding in a print() call in basic_views.py, I see:

{'units': ['s', 'MHz', 's', 's', None], 'dtype': 'ci8', 'shape': [-1, 64, 1, 524288, 2], 'labels': ['time', 'channel', 'time_chunk', 'fine_time', 'pol'], 'scales': [[1494152688.0, 0.17895697066666666], [7437.5, -2.9296875], [0, 0.17895697066666666], [0, -3.413333333333333e-07], None]}

Which seems to suggest that the merge_views is acting on the wrong block. Is this a bug or do I have a stupid typo?

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The more I think about this the less it makes sense :/

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Fantastic!