4377402 262437 262459 416347 1457945 524286
1.99% 1577.82% -0.06% 967.83% -24.01% 774.44%
- 524288 9205096 9453356 9408463 524468 9441930 2218577 9692015
- 9278734 524580 524633 837947 2916107 1048574
+ 524288 9205096 9453356 9408463 524468 9441930 2218577 9692015
+ 9278734 524580 524633 837947 2916107 1048574
1.88% 1693.52% -0.03% 1026.79% -23.92% 824.30%
1048576 19458756 19950272 19838588 1048766 19912134 4430649 20434212
A refinement: The MergeState struct contains the value of min_gallop that
controls when we enter galloping mode, initialized to MIN_GALLOP.
-merge_lo() and merge_hi() adjust this higher when gallooping isn't paying
+merge_lo() and merge_hi() adjust this higher when galloping isn't paying
off, and lower when it is.
the smaller min_gallop gets, making it easier to transition back to
galloping mode (if we ever leave it in the current merge, and at the
start of the next merge). But whenever the gallop loop doesn't pay,
-min_gallop is increased by one, making it harder to transition to back
+min_gallop is increased by one, making it harder to transition back
to galloping mode (and again both within a merge and across merges). For
random data, this all but eliminates the gallop penalty: min_gallop grows
large enough that we almost never get into galloping mode. And for cases
it's unclear how to generalize that intuition usefully, and merging of
wildly unbalanced runs already enjoys excellent performance.
+~sort is a good example of when balanced runs could benefit from a better
+hint value: to the extent possible, this would like to use a starting
+offset equal to the previous value of acount/bcount. Doing so saves about
+10% of the compares in ~sort. However, doing so is also a mixed bag,
+hurting other cases.
+
Comparing Average # of Compares on Random Arrays
------------------------------------------------