I'm not surprised this test takes up more memory... It claims to take up 9 times the test size in memory, with a minimum useful test size of 1G. With a limit of 12G that would make the test size about 1.33G. However, it then proceeds to build a tuple of 159 million distinct integers and stuffs them into a tuple. Each integer is at least 24 bytes long, plus the 8 of the pointer in the tuple, making the total memory use over 32 times the test size. I'll fix the test.