Release Date: 14-December-1994
Question: Versions of the Intel Pentium processor released in 1994 and early 1995 have a floating point co-processor bug. Does this bug affect Neuralyst computations? Does it make a difference if Neuralyst is set to Fixed Calculation Method or Float Calculation Method?
Response: The Pentium floating point co-processor bug is only known to affect floating point division operations and is further characterized by Intel as having a probability of only 1 in 9 billion of occurring for a random pair of numbers. Neuralyst is a computationally intensive application, but Neuralyst performs the bulk of its neural network computations, whether in Fixed or Float Calculation Methods, as additions and multiplies; thus this bug will not affect Neuralyst in the area where it spends the vast majority of its computation time. There are three other areas, where Neuralyst spends much less time and where the low probability of occurrence implies very infrequent events, where the Pentium bug may affect results: (1) rescaling Input, Target, and Output data; (2) calculation of neural network activation functions; and (3) calculation of RMS error and other summary statistics. The calculations performed in these areas are done in floating point regardless of whether Fixed or Float Calculation Method is set. So far as is known at this time, the Pentium bug has a worst case error in the 5th place of precision, with the majority of errors being of much lower significance. None of the three areas listed is likely to be seriously affected by an error in the 5th place of precision. Finally, since Neuralyst is a “fuzzy” tool by nature, it will tend to smooth out small single instance errors or variations over the different cases or the number of epochs used for training. Remember, Neuralyst has an Input Noise parameter specifically for forcing learning in the presence of a simulated noisy environment; the noise levels tolerated by Neuralyst with this parameter set can be many times greater than the errors generated by the Pentium bug.
References: Intel Tech Support; Wall Street Journal - 12/13/94.