Spectral test

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Three-dimensional plot of 100,000 values generated with RANDU. Each point represents 3 consecutive pseudorandom values. It is clearly seen that the points fall in 15 two-dimensional planes.

The spectral test is a statistical test for the quality of a class of pseudorandom number generators (PRNGs), the so-called linear congruential generators (LCGs).[1] As this test is devised to study the lattice structures of LCGs, it can not be applied to other families of PRNGs. According to Donald Knuth,[2] this is by far the most powerful test known, because it can fail LCGs which pass most statistical tests. The IBM subroutine RANDU[3] LCG fails in this test for 3 dimensions and above.


  1. ^ Williams, K. B.; Dwyer, Jerry (1 Aug 1996), "Testing Random Number Generators, Part 2", Dr. Dobb's Journal, retrieved 26 Jan 2012 .
  2. ^ Knuth, Donald E. (1981), The Art of Computer Programming volume 2: Seminumerical algorithms (2nd ed.), Addison-Wesley, p. 89 .
  3. ^ IBM, System/360 Scientific Subroutine Package, Version II, Programmer's Manual, H20-0205-1, 1967, p. 54.