A phase difference compensation element comprises at least one birefringent laminate, which contains a light transmissive base material and \u201ca\u201d number, where a\u22672, of inorganic oblique incidence vacuum deposited films varying in direction of oblique evaporation and having been laminated on a surface of the light transmissive base material. In both implementations log-likelihood ratio metrics on code symbols are estimated as products of various constant values and various combinations of the in-phase and quadrature components of a demodulated soft decision. Each sidewall has an inner shoulder spaced from and parallel to the base. The client is configured to perform search using data records stored on a local machine.