I can't seem to put the right combination of magic into the pg_hba and pg_ident files.

I want to accomplish what I would think would be a simple thing. I
want the root user to be able to connect to the postgres database as
user postgres from the local machine without passwords.  Since I am
doing this from a program I don't want to use the su facility.

I have tried a lot of different combinations of things into the
pg_hba.conf and pg_ident.conf but I can't make anything work.

Here is my pg_ident file

pg_map  root    postgres


Here is the line from pg_hba

local   all         all                               ident map=pg_map

What am I doing wrong here?