message: Changed function description to explain better "availableMemoryProportion" option. Description mostly copied from the poplibs one.
  Reviewers: #tensorflow, jakeh
  Subscribers: davidn, jakeh, stephenm
diff: @@ -242,8 +242,15 @@ def set_matmul_options(opts, matmul_options=None, clear_pass_type=False):
  Args:
  opts: An IpuOptions session control protobuf.
  - matmul_options: A dictionary of poplar option flags for the
  - matrix multiplication operations.
  + matmul_options: A dictionary containing the poplar option flag
  + "availableMemoryProportion" for the matrix multiplication operations.
  + It indicates the proportion of tile memory to be made available as
  + temporary memory for the matrix multiplications (float between 0 and 1.0).
  + Less temporary memory will generally result in a multiplication that
  + takes more cycles to complete. However, because always live memory
  + (like code and vertex state) is not tracked when planning it,
  + a multiplication using less temporary memory may use more memory overall,
  + due to an increase of always live memory.
  clear_pass_type: When set to True, the Pass type will not
  be set in the options passed to the poplar operation.
  