def read_original_smiles(filename):
    """Read mapping of original SMILES for each compound name

    Parameters
    ----------
    filename : str
        File from which molecules are to be read

    Returns
    -------
    original_smiles : dict
        original_smiles[compound_id] is the original SMILES
    """
    original_smiles = dict()
    with open(filename, 'r') as infile:
        for line in infile:
            elements = line.split(',')
            smiles = elements[0]
            cid = elements[1]
            original_smiles[cid] = smiles

    return original_smiles