This is not a good circuit for a precision full wave rectifier.
For positive input voltages the output follows V1 via the bypass resistor R1. Any load on the output will reduce the output voltage.
For negative input voltages the rectifier via U1 is active with a gain of 2 (R3(R2). Settting R3=R2 sets gain=1. Then the output is much more symmetrical, but not identical in both half waves if you add a load. Without load it is nearly ideal.
Look
here for a discussion of the different types of active rectifier.