Performance regression in UFLACS

The following form compiled with UFLACS shows 10 times slow down in dev compared to 2016.1.0. (Note that the form is not very useful as a bilinear form would result in dense UFC element matrix with dimensions (2**8)**2.)

from six.moves import xrange

element = VectorElement("R", triangle, 0, dim=2**8)
v = TestFunction(element)

summands = [v[i]*dx for i in xrange(len(v))]
L = sum(summands)

#L = Form([i for s in summands for i in s.integrals()])

(The last line is a workaround for circumventing a deep recursion in summation (...(s0 + s1) + s2) + s3) + s4) ...) which helps in other cases but is irrelevant here.)

Profiling the code shows 18 million calls to finiteelementbase.py:96(__eq__):

$ python2 -mffc -r uflacs -v -p bug.ufl
$ python2 -mpstats ffc_bug.profile
Welcome to the profile statistics browser.
ffc_bug.profile% sort cumtime
ffc_bug.profile% stats 30
Sun Nov 20 16:21:44 2016    ffc_bug.profile

         35394056 function calls (35334210 primitive calls) in 17.419 seconds

   Ordered by: cumulative time
   List reduced from 1613 to 30 due to restriction <30>

   ncalls  tottime  percall  cumtime  percall filename:lineno(function)
        1    0.000    0.000   17.238   17.238 /home/jan/dev/fenics-master/src/ffc/ffc/__main__.py:84(compile_ufl_data)
        1    0.001    0.001   17.238   17.238 /home/jan/dev/fenics-master/src/ffc/ffc/compiler.py:137(compile_form)
        1    0.000    0.000   17.237   17.237 /home/jan/dev/fenics-master/src/ffc/ffc/compiler.py:158(compile_ufl_objects)
        1    0.000    0.000   16.732   16.732 /home/jan/dev/fenics-master/src/ffc/ffc/representation.py:129(compute_ir)
        1    0.000    0.000   16.637   16.637 /home/jan/dev/fenics-master/src/ffc/ffc/representation.py:425(_compute_integral_ir)
        1    0.000    0.000   16.637   16.637 /home/jan/dev/fenics-master/src/ffc/ffc/uflacs/uflacsrepresentation.py:31(compute_integral_ir)
        1    0.006    0.006   16.627   16.627 /home/jan/dev/fenics-master/src/ffc/ffc/uflacs/representation/build_uflacs_ir.py:40(build_uflacs_ir)
        1    0.000    0.000   16.245   16.245 /home/jan/dev/fenics-master/src/ffc/ffc/uflacs/elementtables/terminaltables.py:359(build_optimized_tables)
        1    0.021    0.021   15.700   15.700 /home/jan/dev/fenics-master/src/ffc/ffc/uflacs/elementtables/terminaltables.py:114(build_element_tables)
      262    0.120    0.000   11.111    0.042 /home/jan/dev/fenics-master/src/ufl/ufl/algorithms/analysis.py:168(sort_elements)
      262    3.836    0.015   10.560    0.040 /home/jan/dev/fenics-master/src/ufl/ufl/utils/sorting.py:26(topological_sorting)
 18222126    4.049    0.000    5.061    0.000 /home/jan/dev/fenics-master/src/ufl/ufl/finiteelement/finiteelementbase.py:96(__eq__)
    66064    0.047    0.000    4.496    0.000 /home/jan/dev/fenics-master/src/ffc/ffc/uflacs/elementtables/terminaltables.py:148(add_table)
      263    0.005    0.000    4.207    0.016 /home/jan/dev/fenics-master/src/ffc/ffc/uflacs/elementtables/table_utils.py:109(get_ffc_table_values)
      260    0.336    0.001    4.184    0.016 /home/jan/dev/fenics-master/src/ffc/ffc/mixedelement.py:66(tabulate)
    65794    0.041    0.000    3.683    0.000 /home/jan/dev/fenics-master/src/ffc/ffc/enrichedelement.py:109(tabulate)
    65809    0.316    0.000    3.644    0.000 /home/jan/dev/fenics-master/src/fiat/FIAT/finite_element.py:175(tabulate)
    65809    0.250    0.000    3.238    0.000 /home/jan/dev/fenics-master/src/fiat/FIAT/polynomial_set.py:84(tabulate)
    65814    0.155    0.000    2.322    0.000 /home/jan/dev/fenics-master/src/fiat/FIAT/expansions.py:202(tabulate)
    65815    0.927    0.000    2.017    0.000 /home/jan/dev/fenics-master/src/fiat/FIAT/expansions.py:208(_tabulate)
   132702    0.470    0.000    1.268    0.000 {sum}
  2598597    0.423    0.000    1.204    0.000 /home/jan/dev/fenics-master/src/ufl/ufl/finiteelement/finiteelementbase.py:86(_ufl_hash_data_)
2913599/2913593    0.604    0.000    0.871    0.000 {repr}
   131385    0.771    0.000    0.771    0.000 {method 'remove' of 'list' objects}
   136854    0.758    0.000    0.758    0.000 {method 'pop' of 'list' objects}
   394890    0.587    0.000    0.588    0.000 /home/jan/dev/fenics-master/src/fiat/FIAT/expansions.py:212(<genexpr>)
        1    0.001    0.001    0.544    0.544 /home/jan/dev/fenics-master/src/ffc/ffc/uflacs/elementtables/terminaltables.py:196(optimize_element_tables)
      260    0.086    0.000    0.527    0.002 /home/jan/dev/fenics-master/src/ffc/ffc/uflacs/elementtables/table_utils.py:57(strip_table_zeros)
    65814    0.252    0.000    0.441    0.000 /usr/lib/python2.7/dist-packages/numpy/linalg/linalg.py:1924(norm)
    65833    0.121    0.000    0.415    0.000 /home/jan/dev/fenics-master/src/fiat/FIAT/polynomial_set.py:201(form_matrix_product)

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