anchor.diff:  
   # Install mpi4py.
   
  -RUN source /etc/profile.d/desi.sh \
  -    && curl -SL https://pypi.python.org/packages/ee/b8/f443e1de0b6495479fc73c5863b7b5272a4ece5122e3589db6cd3bb57eeb/mpi4py-2.0.0.tar.gz#md5=4f7d8126d7367c239fd67615680990e3 \
  +RUN curl -SL https://pypi.python.org/packages/ee/b8/f443e1de0b6495479fc73c5863b7b5272a4ece5122e3589db6cd3bb57eeb/mpi4py-2.0.0.tar.gz#md5=4f7d8126d7367c239fd67615680990e3 \
       -o mpi4py-2.0.0.tar.gz \
       && tar xzf mpi4py-2.0.0.tar.gz \
       && cd mpi4py-2.0.0 \
  
positive.code: 
  # Install FFTW.
  
  RUN source /etc/profile.d/desi.sh \
      && curl -SL http://www.fftw.org/fftw-3.3.5.tar.gz \
      -o fftw-3.3.5.tar.gz \
      && tar xzf fftw-3.3.5.tar.gz \
      && cd fftw-3.3.5 \
  
negative.code: # or other TCL based scripts, it should be OK to have the
  # conda TCL/TK installation in our LD_LIBRARY_PATH.
  
  # At run time, the user must specify the mount points for 
  # /desi/spectro_data, /desi/spectro_redux, /desi/root,
  # and /desi/model.  The user must also set the environment 
  # variable for SPECPROD.  Currently DESI_BASIS_TEMPLATES 
  # is hard-coded to a subdirectory of DESI_ROOT, but we 
  # should change that.
  
  ENV PATH /usr/local/bin:/usr/local/conda/bin:/usr/bin:/bin:/usr/sbin:/sbin
  ENV CPATH /usr/local/include:/usr/local/conda/include:/usr/include
  ENV LIBRARY_PATH /usr/local/lib:/usr/local/conda/lib:/usr/lib
  ENV LD_LIBRARY_PATH /usr/local/lib:/usr/local/conda/lib:/usr/lib
  ENV PYTHONPATH /usr/local/lib/python3.5/site-packages
  
  ENV DESI_ROOT /desi/root
  ENV DESIMODEL /desi/model
  ENV DESI_SPECTRO_DATA /desi/spectro_data
  ENV DESI_SPECTRO_REDUX /desi/spectro_redux
  ENV DESI_BASIS_TEMPLATES "${DESI_ROOT}/spectro/templates/basis_templates/v2.2"
  
  # Create working directory for builds
  
  