J is a general-purpose language. It is oriented toward math and data handling far more than K. Speed relative to K, for example, is largely dependent upon what

J is a general-purpose language. It is oriented toward math and data handling far more than K. Speed relative to K, for example, is largely dependent upon what operators are used, with what size and shape of data. Certain operations in J are highly optimized, comparable to C (or exceeding) what you'd find in matrix math libraries.