[Haskell-cafe] proper way to generate a random data in criterion

Hello, I'm measuring performance of the insertion operation of red-black trees. For input, three kinds of [Int] are prepared: the increasing the order, decreasing order, and random. The random case is 4 or 5 times slower than the others. I'm afraid that my program also measured the cost of random Int generation. My benchmark code can be found: https://github.com/kazu-yamamoto/llrbtree/blob/master/bench/insert/Bench.hs Does anyone kindly take a look and tell me whether or not my criterion code measures the cost of random Int generation? If so, would you suggest how to avoid it? Background infromation can be found: Purely Functional Left-Leaning Red-Black Trees http://www.mew.org/~kazu/proj/red-black-tree/ --Kazu