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120 lines
2.9 KiB
C
120 lines
2.9 KiB
C
// (c) 2010 Thomas Schoebel-Theuer / 1&1 Internet AG
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// (c) 2012 Thomas Schoebel-Theuer
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#ifndef LIB_RANK_H
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#define LIB_RANK_H
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/* Generic round-robin scheduler based on ranking information.
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*/
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#define RKI_DUMMY INT_MIN
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struct rank_info {
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int rki_x;
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int rki_y;
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};
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struct rank_data {
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// public readonly
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long long rkd_current_points;
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// private
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long long rkd_tmp;
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long long rkd_got;
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};
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/* Ranking phase.
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*
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* Calls should follow the following usage pattern:
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*
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* ranking_start(...);
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* for (...) {
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* ranking_compute(&rkd[this_time], ...);
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* // usually you need at least 1 call for each rkd[] element,
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* // but you can call more often to include ranking information
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* // from many different sources.
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* // Note: instead / additionally, you may also use
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* // ranking_add() or ranking_override().
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* }
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* ranking_stop(...);
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*
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* => now the new ranking values are computed and already active
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* for the round-robin ranking_select() mechanism described below.
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*
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* Important: the rki[] array describes a ranking function at some
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* example points (x_i,y_i) which must be ordered according to x_i
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* in ascending order. And, of course, you need to supply at least
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* two sample points (otherwise a linear function cannot
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* be described).
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* The array _must_ always end with a dummy record where the x_i has the
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* value RKI_DUMMY.
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*/
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extern inline
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void ranking_start(struct rank_data rkd[], int rkd_count)
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{
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int i;
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for (i = 0; i < rkd_count; i++) {
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rkd[i].rkd_tmp = 0;
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}
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}
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extern void ranking_compute(struct rank_data *rkd, const struct rank_info rki[], int x);
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/* This may be used to (exceptionally) add some extra salt...
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*/
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extern inline
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void ranking_add(struct rank_data *rkd, int y)
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{
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rkd->rkd_tmp += y;
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}
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/* This may be used to (exceptionally) override certain ranking values.
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*/
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extern inline
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void ranking_override(struct rank_data *rkd, int y)
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{
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rkd->rkd_tmp = y;
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}
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extern inline
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void ranking_stop(struct rank_data rkd[], int rkd_count)
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{
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int i;
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for (i = 0; i < rkd_count; i++) {
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rkd[i].rkd_current_points = rkd[i].rkd_tmp;
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}
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}
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/* This is a round-robin scheduler taking her weights
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* from the previous ranking phase (the more ranking points,
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* the more frequently a candidate will be selected).
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*
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* Typical usage pattern (independent from the above ranking phase
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* usage pattern):
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*
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* while (__there_is_work_to_be_done(...)) {
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* int winner = ranking_select(...);
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* if (winner >= 0) {
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* __do_something(winner);
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* ranking_select_done(..., winner, 1); // or higher, winpoints >= 1 must hold
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* }
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* ...
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* }
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*
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*/
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extern int ranking_select(struct rank_data rkd[], int rkd_count);
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extern inline
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void ranking_select_done(struct rank_data rkd[], int winner, int win_points)
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{
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if (winner >= 0) {
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if (win_points < 1)
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win_points = 1;
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rkd[winner].rkd_got += win_points;
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}
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}
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#endif
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