This function was written by Mark Seligman at Rapid Biologics,
gpuLm.fit calls this function
to determine a default tolerance. So gpuLm.defaultTol should
not need to be used directly.
logical. If TRUE, a tolerance will be returned appropriate for single precision arithmetic. If FALSE, a tolerance will be returned appropriate for double precision arithmetic.
a floating point number representing a tolerance to be used by gpuLm.fit