I'm relatively new to Common Lisp. GCL has been my preferred CL platform (over CMUCL and CLisp) because it generates portable C code and then calls a compiler. I recently was trying to sum a large list of numbers using reduce, and GCL took a very long time to compute the result. I'm trying to understand why.
In GCL, it takes ~852 seconds to sum 200000 integers:
>(defun range (start end) (loop for i from start below end collect i)) RANGE