SSSP validation broken for infinity output

[mihaic]

Using validation graph from:
https://s3-eu-west-1.amazonaws.com/graphalytics-graphs/index.html

The result contains numeric_limits<int64_t>::max(), but the validation expects Infinity:

18:34:31.206 [INFO ] Validating contents of '/var/scratch/mcapota/output-graphmat-s/datagen-300-SSSP'...
18:34:43.340 [INFO ]  - Vertex 6 has value '9.223372036854776E18', but valid value is 'Infinity'

[thegeman]

SSSP uses double precision floating point numbers. As infinity we accept either a textual representation as produced by most porgramming languages, such as inf or infinity, or the largest positive (smallest negative) number presentable in the IEEE 754 double precision format (with some room for rounding errors due to printing and parsing). @stijnh can elaborate if anything is unclear about the implementation of this in our validation.

[mihaic]

@stijnh had previously informed me that "inf" is not a valid output value for BFS, and the validation code indeed does not accept "inf", only numeric_limits<int64_t>::max(). Please make it clear in the specification what the representation of infinity should be for all algorithms.