1. A method to operate a computing machine to rate the validity of a data processing algorithm A on input data I, wherein the input data is processed by the data processing algorithm to produce output data P, the method including: generating one or both of phase representations and phase congruence representations of the input data, including: (1) computing an n Dimensional Fourier Transform or discrete cosine transform of the input data, and (2) computing the phase of the transform computed at (1); and generating one or both of phase representations and phase congruence representations of the output data, including: (3) computing an n Dimensional Fourier Transform or discrete cosine transform of the output data, and (4) computing the phase of the transform computed at (3); generating a similarity metric of one or both of the generated phase representations and phase congruence representations of the input data with one or both of the generated phase representations and phase congruence representations of the output data, including (5) computing the normalized cross correlation mean absolute phase difference (MAPD), normalized mean square error (NMSE) or scale invariant normalized mean square error (S1NMSE) of the input data transform phase computed at (2) with the output data transform phase computed at (4); and wherein the generated similarity metric is a value representative of the validity of the data processing algorithm and is free from use of a ground truth.