clojure.pprint/cl-format is slow
Had a serious performance problem last week. After some digging we narrowed it down to a call to cl-format.
Some test code to demonstrate the discrepancy:
With the following results. For the simple case, cl-format is 10 times slower than a simple string return. For more complicated format strings, closer to 100 times slower:
Having a quick look at the implementation of cl-format I immediately noticed a compile-format function which seems like something that might help out with performance for many calls to a cl-format with the same format string:
Compiles format-str into a compiled format which can be used as an argument to cl-format just like a plain format string. Use this function for improved performance when you're using the same format string repeatedly
It also seems like cl-format will check if it's format string is already compiled and skip compilation if that is the case:
Oddly however, compile-format is not public, so I can't use it. So I am left a little confused. I am going to do some more digging tomorrow to solve this mystery as I am sure I am missing something here.
Not sure if pre-compilation will help solve the horrible performance you get from cl-format, but I am guessing it might help.
After some discussion with my colleagues, it seems I haven't missed anything and we think this is a bug.
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