Using the benchmarks in the Oj test directory Oj has a slight advantage over the core json for dumping but not enough to make much difference. The comparison for Oj strict parsing compared to the core json is more substantial as 1.37 times faster. The benchmarks use a hash of mixed types included some nested elements.
The callback parsers (Saj and Scp) also show a performance advantage as does the most recent Oj::Parser.
As for the dumping of floats that are at the edge of precision (16 places), Oj does round to to 15 places if the last 4 of a 16 digit float is "0001" or "9999" if the float precision is not set to zero. That is intentional. If that is not the desired behavior and the Ruby conversion is preferred then setting the float precision to zero will not round. You picked the wrong options for your example.
I would like to say that the core json has a come a very long way since Oj was created and is now outstanding. If the JSON gem had started out where it is now I doubt I would have bothered writing Oj.
The callback parsers (Saj and Scp) also show a performance advantage as does the most recent Oj::Parser.
As for the dumping of floats that are at the edge of precision (16 places), Oj does round to to 15 places if the last 4 of a 16 digit float is "0001" or "9999" if the float precision is not set to zero. That is intentional. If that is not the desired behavior and the Ruby conversion is preferred then setting the float precision to zero will not round. You picked the wrong options for your example.
I would like to say that the core json has a come a very long way since Oj was created and is now outstanding. If the JSON gem had started out where it is now I doubt I would have bothered writing Oj.