pathological fold performance

foldtest.clj

(ns foldtest
  (:require [clojure.core.reducers :as r]))
 
;; redefined to parameterize the threshold to r/fold
(defn foldcat [n coll]
  (r/fold n r/cat r/append! coll))
 
(defn benchmark [n]
  (let [x (into [] (range 1e8))]
    (println "init vec")
    (dotimes [_ n]
    (time (foldcat 4096 (r/map inc x))))))
 
(defn -main [n]
  (benchmark (Long/parseLong n)))