### clean_zeros -- Eliminate zero coefficients

        call a%clean_zeros(info)

Eliminates zero coefficients in the input matrix. Note that depending on the internal storage format, there may still be some amount of zero padding in the output.

Type:
  Asynchronous.
On Entry
a
  the sparse matrix.
  A variable of type `psb_Tspmat_type`.
  Scope: local.

On Return
a
  The matrix `a` without zero coefficients.
  A variable of type `psb_Tspmat_type`.
info
  Return code.