tools/lib/list_sort.c

14 __attribute__((nonnull(2,3,4)))
50 __attribute__((nonnull(2,3,4,5)))
129  * 2:1 balanced merges.  Given two pending sublists of size 2^k, they are
130  * merged to a size-2^(k+1) list as soon as we have 2^k following elements.
132  * Thus, it will avoid cache thrashing as long as 3*2^k elements can
141  * Each time we increment "count", we set one bit (bit k) and clear
142  * bits k-1 .. 0.  Each time this happens (except the very first time
143  * for each bit, when count increments to 2^k), we merge two lists of
144  * size 2^k into one list of size 2^(k+1).
147  * 2^k, which is when we have 2^k elements pending in smaller lists,
148  * so it's safe to merge away two lists of size 2^k.
150  * After this happens twice, we have created two lists of size 2^(k+1),
151  * which will be merged into a list of size 2^(k+2) before we create
152  * a third list of size 2^(k+1), so there are never more than two pending.
154  * The number of pending lists of size 2^k is determined by the
155  * state of bit k of "count" plus two extra pieces of information:
157  * - The state of bit k-1 (when k == 0, consider bit -1 always set), and
159  *   is count >= 2^(k+1)).
163  * 0:  00x: 0 pending of size 2^k;           x pending of sizes < 2^k
164  * 1:  01x: 0 pending of size 2^k; 2^(k-1) + x pending of sizes < 2^k
165  * 2: x10x: 0 pending of size 2^k; 2^k     + x pending of sizes < 2^k
166  * 3: x11x: 1 pending of size 2^k; 2^(k-1) + x pending of sizes < 2^k
167  * 4: y00x: 1 pending of size 2^k; 2^k     + x pending of sizes < 2^k
168  * 5: y01x: 2 pending of size 2^k; 2^(k-1) + x pending of sizes < 2^k
171  * We gain lists of size 2^k in the 2->3 and 4->5 transitions (because
172  * bit k-1 is set while the more significant bits are non-zero) and
174  * before the 5->2 transition, all lower-order bits are 11 (state 3),
180  * of size 2^k varies from 2^(k-1) (cases 3 and 5 when x == 0) to
181  * 2^(k+1) - 1 (second merge of case 5 when x == 2^(k-1) - 1).
183 __attribute__((nonnull(2,3)))