Branch FastSortSm20 radix_sort fails to handle floating point key ranges between 1.0 and 2.0

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What steps will reproduce the problem?
1. Given a key array of floating points (float or double) and a value array of 
integer. For example: 
  //key[i] = (double)N / (double)i; 
  double key[5]   = [0.0, 5.0, 2.5, 1.66667, 1.25 ] ; 
  int    value[5] = [0, 1, 2, 3, 4] ;

2. Use the radix_sort from Branch FastSortSm20. The key value between 1.xx will 
be greater than any other elements.
  The output is

    key[] = [0, 2.5, 5, 1.25, 1.66667 ]     
  value[] = [0, 2, 1, 4, 3, ]


3. Use the radix_sort in trunk gives the correct result.

    key[] = [0, 1.25, 1.66667, 2.5, 5 ]     
  value[] = [0, 4, 3, 2, 1 ]


What version of the product are you using? On what operating system?

Ubuntu 10.10 x64
CUDA 4.0 (GPU GTX 470)
r893, branches/FastSortSm20
r893, trunk

Please provide any additional information below.

I want to sort the elements in each row vector of a floating poinrt 2D matrix. 
The Entactor::SmallSort() interface in the branch FastSortSm20 seems a good 
fit. Even better, it allows specifying cudaStream in the interface. I want to 
split the row vectors by several streams to utilize the concurrent kernel 
execution. Note that the Compute Capability 2.0 hardware supports 16 concurrent 
kernels.

Original issue reported on code.google.com by addee2...@gmail.com on 3 Jul 2012 at 10:26