I imagine that in this program when Double isn't specified the compiler doesn't assign a "hardware optimized" number type. Consequently it isn't using the specialized functions that are used for 64-bit floating point numbers. When the program specifies it is receiving the "Double" values, then it does use the "hardware optimized" data types.

On Wed, May 4, 2016 at 3:12 PM, Ben Rogalski <bwrogalski@gmail.com> wrote:

I have found that using the type Double in a type signature causes my program to run much faster than if I use a type variable with a Num constraint.

Is this common, and if so, why is explicitly using Double faster?

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