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Monday, January 28, 2008

ENT (Pseudorandom Sequence Test Program) Updated

I have just posted an update to ENT, the pseudorandom sequence test program which was one of the first pieces of software to be posted on the Fourmilab site in 1994 (updates were subsequently released in 1998 and 2006).

Among the statistics ENT computes for the sequence tested is a chi-square value comparing the sequence's distribution of values to that expected for a uniformly distributed random sequence. In addition to the chi-square value, an interpretation of it in terms of the probability of the sequence's being random was output. This probability value was obtained by a tacky table look-up, which simply yielded a rough estimate of the probability within a series of bands. This update includes numerical evaluation of actual probability from the measured chi-square value. If the computed chance probability is less than 0.01% or greater than 99.99% it is labeled as such.

The 16-bit MS-DOS executable included with earlier releases has been supplanted by a Win32 executable built with Microsoft Visual C++ 7.0; this binary does not require loading the 16-bit compatibility module on 32-bit Windows platforms (but of course only runs on the latter). This update corrects a problem which caused errors when processing data piped to standard input on Windows platforms: standard input is now set to the required binary mode.

Posted at January 28, 2008 20:56