Sometimes TIME results produce negative values. Why?
As an example, see the below output CL-USER(12): (time (fib 30)) ; cpu time (non-gc) 36,784 msec user, 140 msec system ; cpu time (gc) 3,994 msec user, 10 msec system ; cpu time (total) 40,778 msec user, 150 msec system ; real time 51,274 msec ; space allocation: ; 60,582,248 cons cells, -934,589,280 other bytes, 0 static bytes 1346269 CL-USER(13): The problem is with the overflow of machine integers. On 32-bit platforms, the allocator, which resides in low level C code, keeps track of counts using 32-bit variables. As these allocations occur over time, these variables can in fact overflow resulting in the negative output seen above. It would be a simple matter to adjust such values in the case where an overflow occurs only once (the typical case), by adding #x100000000 (4 GB) to the negative value. But because we cannot determine how many overflows actually occured, we choose not to adjust in all cases where negative space is reported as that would give wholly false (but apparently va
