Introduce ULP Based Floating Point Equality Test to Device Function

[isVoid]

Description

This PR adds float_eq_by_ulp utility to allow practical near equality for floating point computation in device code.

In GIS application, near equal is often required due to rounding error of floating point and may wrong categorization of line collinearity or point on line test.

Using this test does not incur visible performance degradation:

$ python ~/scratch/nvbench/scripts/nvbench_compare.py naive.json ulp.json 
['naive.json', 'ulp.json']
# floating_point_equivalence_benchmark

## [0] Tesla V100-SXM2-32GB

|  FloatingPointType  |  NumFloats  |   Ref Time |   Ref Noise |   Cmp Time |   Cmp Noise |      Diff |   %Diff |  Status  |
|---------------------|-------------|------------|-------------|------------|-------------|-----------|---------|----------|
|         F32         |   100000    |   2.617 us |      55.95% |   2.478 us |      53.16% | -0.139 us |  -5.30% |   PASS   |
|         F32         |   1000000   |   2.508 us |      59.48% |   2.471 us |      53.17% | -0.037 us |  -1.49% |   PASS   |
|         F32         |  10000000   |   2.509 us |      58.42% |   2.553 us |      52.45% |  0.044 us |   1.76% |   PASS   |
|         F32         |  100000000  |   2.612 us |      56.19% |   2.483 us |      55.23% | -0.129 us |  -4.94% |   PASS   |
|         F64         |   100000    |   2.501 us |      72.35% |   2.483 us |      54.59% | -0.018 us |  -0.72% |   PASS   |
|         F64         |   1000000   |   2.514 us |      60.63% |   2.564 us |      55.11% |  0.050 us |   1.98% |   PASS   |
|         F64         |  10000000   |   2.609 us |      56.87% |   2.492 us |      56.80% | -0.117 us |  -4.48% |   PASS   |
|         F64         |  100000000  |   2.519 us |      61.38% |   2.495 us |      57.26% | -0.025 us |  -0.98% |   PASS   |

Note that the run time is very small in time scale so the result is very noisy. The average time difference is very small though.

Checklist

• I am familiar with the Contributing Guidelines.
• New or existing tests cover these changes.
• The documentation is up to date with these changes.

[thomcom]

Wow, I'm really impressed.

[harrism]

Very useful!

[isVoid]

rerun tests

[harrism]

@gpucibot merge