Add units #42

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1. zingale

   added

   enhancement

   on Jul 8, 2018
2. zingale commented on Jul 30, 2018

   

   zingale

   on Jul 30, 2018

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   yt-project/unyt#39
3. harpolea commented on Aug 10, 2018

   

   harpolea

   on Aug 10, 2018

   Last edited by harpolea

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   @mojiastonybrook: Looking at https://github.com/python-hydro/pyro2/blob/units/mesh/array_indexer.py in 35f74c4, I've noticed a couple of things:

   • The copy function does not copy over the units. Compare the pyro version
     

     pyro2/mesh/array_indexer.py

     Lines 114 to 116 in 35f74c4

     	def copy(self):
     	"""make a copy of the array, defined on the same grid"""
     	return ArrayIndexer(np.asarray(self).copy(), grid=self.g)

     
     vs the unyt version
     https://github.com/yt-project/unyt/blob/679a4473e8944a9a55f7ffc0a72f569e6c23d85e/unyt/array.py#L1683-L1717

   • When I tried running the smooth problem using the advection solver, I noticed that the code was failing when it tries to create new ArrayIndexer objects here

     pyro2/advection/advective_fluxes.py

     Lines 98 to 99 in 35f74c4

     	F_xt = u*a_x
     	F_yt = v*a_y

     F_xt and F_yt are defined here as the product of a scalar and an ArrayIndexer object, however they have not been correctly initialized with grids. It looks like unyt does some clever stuff with multiplication in https://github.com/yt-project/unyt/blob/679a4473e8944a9a55f7ffc0a72f569e6c23d85e/unyt/array.py#L1535-L1681 to ensure consistency of units, so we may need to create some wrapper for this that adds the grids back in.
     I managed to fix this by initializing the arrays first:

       F_xt = myg.scratch_array()
       F_yt = myg.scratch_array()
       F_xt[:,:] = u*a_x
       F_yt[:,:] = v*a_y