Query: Spatially uncorrelated reproducible random values

[Nigel Gilbert]

Can anyone suggest an algorithm that I can use to map from a vector 
of integers to an integer, such that there is no correlation between 
the magnitudes of the input values and the output, yet the same input 
always generates the same output?

To clarify this, let me give the context:

I am writing a simulation that explores a "random" multi-dimensional 
fitness landscape.  For each location on the landscape there is a 
corresponding fitness value.  This value is uncorrelated with the 
location.  I _could_ use a standard random number generator to create 
the landscape represented as a multi-dimensional array, by traversing 
the array and storing the next sequential value from the generator at 
each successive array element.  Later, when I need to find the 
fitness at a particular location, I could just look up the value at 
the appropriate coordinates in the array.  However, the landscape is 
potentially vast and the storage needed for the array is therefore 
unreasonable, especially since fitness values at only a few locations 
will be required in any one run.  Thus what I need is a function that 
has the location coordinates as inputs and the fitness value as the 
output, where the fitness value is a random number with no 'spatial' 
correlation with the coordinates.

Conventional discussions of random number generators assume that what 
you want is a random number stream, rather than a random mapping. Any 
ideas?

Many thanks

Nigel Gilbert
--
______________________________________________________________________________
Prof Nigel Gilbert, PhD, FREng, Department of Sociology, University of Surrey,
     Guildford GU2 5XH, UK. Tel: +44 1483 259173 Fax: +44 1483 259551


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