Last month I wrote:
> It seems clear that our qsort.c is doing a pretty awful job of picking
> qsort pivots, while glibc is mostly managing not to make that mistake.
I re-ran Gary's test script using the just-committed improvements to
qsort.c, and got pretty nice numbers (attached --- compare to
http://archives.postgresql.org/pgsql-performance/2006-02/msg00227.php).
So it was wrong to blame his problems on the pivot selection --- the
culprit was that ill-considered switch to insertion sort.
regards, tom lane
100 runtimes for latest port/qsort.c, sorted ascending:
Time: 335.481 ms
Time: 335.606 ms
Time: 335.932 ms
Time: 336.039 ms
Time: 336.182 ms
Time: 336.231 ms
Time: 336.711 ms
Time: 336.721 ms
Time: 336.971 ms
Time: 336.982 ms
Time: 337.036 ms
Time: 337.190 ms
Time: 337.223 ms
Time: 337.312 ms
Time: 337.350 ms
Time: 337.423 ms
Time: 337.523 ms
Time: 337.528 ms
Time: 337.565 ms
Time: 337.566 ms
Time: 337.732 ms
Time: 337.741 ms
Time: 337.744 ms
Time: 337.786 ms
Time: 337.790 ms
Time: 337.898 ms
Time: 337.905 ms
Time: 337.952 ms
Time: 337.976 ms
Time: 338.017 ms
Time: 338.123 ms
Time: 338.206 ms
Time: 338.306 ms
Time: 338.514 ms
Time: 338.594 ms
Time: 338.597 ms
Time: 338.683 ms
Time: 338.705 ms
Time: 338.729 ms
Time: 338.748 ms
Time: 338.816 ms
Time: 338.958 ms
Time: 338.963 ms
Time: 338.997 ms
Time: 339.074 ms
Time: 339.106 ms
Time: 339.134 ms
Time: 339.159 ms
Time: 339.226 ms
Time: 339.260 ms
Time: 339.289 ms
Time: 339.341 ms
Time: 339.500 ms
Time: 339.585 ms
Time: 339.595 ms
Time: 339.774 ms
Time: 339.897 ms
Time: 339.927 ms
Time: 340.064 ms
Time: 340.133 ms
Time: 340.172 ms
Time: 340.219 ms
Time: 340.261 ms
Time: 340.323 ms
Time: 340.708 ms
Time: 340.761 ms
Time: 340.785 ms
Time: 340.900 ms
Time: 340.986 ms
Time: 341.339 ms
Time: 341.564 ms
Time: 341.707 ms
Time: 342.155 ms
Time: 342.213 ms
Time: 342.452 ms
Time: 342.515 ms
Time: 342.540 ms
Time: 342.928 ms
Time: 343.548 ms
Time: 343.663 ms
Time: 344.192 ms
Time: 344.952 ms
Time: 345.152 ms
Time: 345.174 ms
Time: 345.444 ms
Time: 346.848 ms
Time: 348.144 ms
Time: 348.842 ms
Time: 354.550 ms
Time: 356.877 ms
Time: 357.475 ms
Time: 358.487 ms
Time: 364.178 ms
Time: 370.730 ms
Time: 493.098 ms
Time: 648.009 ms
Time: 849.345 ms
Time: 860.616 ms
Time: 936.800 ms
Time: 1727.085 ms
