rbyd-rr: Consolidated all pruning before flips and stuff
This adds lfsr_tag_prune to compliment lfsr_tag_prune2, and deduplicates all of the reachability-related pruning logic to before any tree mutation occurs for red/black flips, yellow splits, etc. The previous, post-flips logic was arguably simpler and more mistake-proof, but moving pruning logic pre-flips ensures we don't miss any prunability due to yellow splits. This is the reason diverged pruning _must_ occur pre-flips. And code deduplication is always nice. Note lfsr_tag_prune is _not_ the same as lfsr_tag_unreachable it replaces. The prune functions check for both unreachability and only-reachability to determine if an alt should be pruned.
This commit is contained in:
Christopher Haster
@@ -914,43 +914,6 @@ static inline bool lfsr_tag_follow2(
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return lfsr_tag_follow(alt, weight, lower, upper, rid, tag);
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}
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static inline bool lfsr_tag_prune2(
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lfsr_tag_t alt, lfsr_rid_t weight,
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lfsr_tag_t alt2, lfsr_rid_t weight2,
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lfsr_srid_t lower_rid, lfsr_srid_t upper_rid,
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lfsr_tag_t lower_tag, lfsr_tag_t upper_tag) {
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if (lfsr_tag_isgt(alt)) {
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return lfsr_tag_follow2(
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alt, weight,
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alt2, weight2,
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lower_rid, upper_rid,
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lower_rid-1, lower_tag+1);
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} else {
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return lfsr_tag_follow2(
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alt, weight,
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alt2, weight2,
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lower_rid, upper_rid,
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upper_rid-1, upper_tag-1);
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}
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}
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static inline bool lfsr_tag_unreachable(
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lfsr_tag_t alt, lfsr_rid_t weight,
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lfsr_srid_t lower_rid, lfsr_srid_t upper_rid,
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lfsr_tag_t lower_tag, lfsr_tag_t upper_tag) {
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if (lfsr_tag_isgt(alt)) {
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return !lfsr_tag_follow(
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alt, weight,
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lower_rid, upper_rid,
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upper_rid-1, upper_tag-1);
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} else {
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return !lfsr_tag_follow(
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alt, weight,
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lower_rid, upper_rid,
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lower_rid-1, lower_tag+1);
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}
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}
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static inline void lfsr_tag_flip(
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lfsr_tag_t *alt, lfsr_rid_t *weight,
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lfsr_srid_t lower, lfsr_srid_t upper) {
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@@ -1003,6 +966,54 @@ static inline void lfsr_tag_trim2(
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lower_tag, upper_tag);
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}
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static inline bool lfsr_tag_prune(
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lfsr_tag_t alt, lfsr_rid_t weight,
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lfsr_srid_t lower_rid, lfsr_srid_t upper_rid,
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lfsr_tag_t lower_tag, lfsr_tag_t upper_tag) {
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if (lfsr_tag_isgt(alt)) {
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// unreachable?
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return !lfsr_tag_follow(
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alt, weight,
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lower_rid, upper_rid,
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upper_rid-1, upper_tag-1)
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// only-reachable?
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|| lfsr_tag_follow(
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alt, weight,
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lower_rid, upper_rid,
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lower_rid-1, lower_tag+1);
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} else {
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// unreachable?
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return !lfsr_tag_follow(
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alt, weight,
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lower_rid, upper_rid,
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lower_rid-1, lower_tag+1)
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// only-reachable?
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|| lfsr_tag_follow(
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alt, weight,
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lower_rid, upper_rid,
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upper_rid-1, upper_tag-1);
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}
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}
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static inline bool lfsr_tag_prune2(
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lfsr_tag_t alt, lfsr_rid_t weight,
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lfsr_tag_t alt2, lfsr_rid_t weight2,
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lfsr_srid_t lower_rid, lfsr_srid_t upper_rid,
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lfsr_tag_t lower_tag, lfsr_tag_t upper_tag) {
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if (lfsr_tag_isred(alt2)) {
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lfsr_tag_trim(
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alt2, weight2,
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&lower_rid, &upper_rid,
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&lower_tag, &upper_tag);
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}
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return lfsr_tag_prune(
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alt, weight,
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lower_rid, upper_rid,
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lower_tag, upper_tag);
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}
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// support for encoding/decoding tags on disk
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// tag encoding:
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@@ -2965,32 +2976,19 @@ again:;
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// goto prune;
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// }
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// prune?
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// <b >b
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// .-'| .-'|
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// <y | | |
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// .-------'| | | |
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// | <r | => | <b
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// | .----' | .-----------|-'|
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// | | <b | <b |
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// | | .----'| | .----'| |
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// 1 2 3 4 4 1 2 3 4 4 2
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if (lfsr_tag_prune2(
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alt, weight,
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p_alts[0], p_weights[0],
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lower_rid, upper_rid,
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lower_tag, upper_tag)
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// prune because of diverged paths?
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|| (lfsr_d_isdiverged(d_state)
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&& (d_state == LFSR_D_DIVERGEDUPPER)
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^ lfsr_tag_isgt(alt)
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^ lfsr_tag_follow2(
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alt, weight,
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p_alts[0], p_weights[0],
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lower_rid, upper_rid,
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a_rid, a_tag))) {
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// prune because of diverged paths?
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if (lfsr_d_isdiverged(d_state)
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&& (d_state == LFSR_D_DIVERGEDUPPER)
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^ lfsr_tag_isgt(alt)
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^ lfsr_tag_follow2(
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alt, weight,
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p_alts[0], p_weights[0],
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lower_rid, upper_rid,
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a_rid, a_tag)) {
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// note, yellow prunes always follow and have no weight, it's
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// only diverged pruning that needs all these special cases
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// eagerly flip in case we are ambiguous yellow alts
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if (lfsr_tag_follow2(
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alt, weight,
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p_alts[0], p_weights[0],
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@@ -3007,6 +3005,56 @@ again:;
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&lower_rid, &upper_rid,
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&lower_tag, &upper_tag);
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// red alts we can collapse
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if (lfsr_tag_isred(p_alts[0])) {
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printf("%04x->%04x: drprune 0x%x w%d\n",
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branch,
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rbyd->eoff,
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alt,
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weight);
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goto prune;
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// black alts just become unreachable, if we pruned these
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// it would break the coloring of our tree
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} else {
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printf("%04x->%04x: dbprune 0x%x w%d\n",
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branch,
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rbyd->eoff,
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alt,
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weight);
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alt = LFSR_TAG_ALT(LFSR_TAG_LE, LFSR_TAG_B, 0);
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weight = 0;
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// jump = 0;
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}
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}
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// prune?
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// <b >b
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// .-'| .-'|
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// <y | | |
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// .-------'| | | |
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// | <r | => | <b
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// | .----' | .-----------|-'|
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// | | <b | <b |
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// | | .----'| | .----'| |
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// 1 2 3 4 4 1 2 3 4 4 2
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if (lfsr_tag_prune2(
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alt, weight,
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p_alts[0], p_weights[0],
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lower_rid, upper_rid,
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lower_tag, upper_tag)) {
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// note, yellow prunes always follow and have no weight, it's
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// only diverged pruning that needs all these special cases
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// eagerly flip in case we are ambiguous yellow alts
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if (lfsr_tag_follow2(
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alt, weight,
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p_alts[0], p_weights[0],
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lower_rid, upper_rid,
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a_rid, a_tag)) {
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lfs_swap32(&jump, &branch_);
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}
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// red alts we can collapse
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if (lfsr_tag_isred(p_alts[0])) {
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printf("%04x->%04x: yrprune 0x%x w%d\n",
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@@ -3148,84 +3196,15 @@ again:;
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lower_rid, upper_rid);
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lfs_swap32(&jump, &branch_);
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}
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// red unreachable? prune
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if (lfsr_tag_unreachable(
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p_alts[0], p_weights[0],
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lower_rid, upper_rid,
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lower_tag, upper_tag)) {
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printf("%04x->%04x: rprune 0x%x w%d\n",
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branch,
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rbyd->eoff,
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p_alts[0],
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p_weights[0]);
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lfsr_tag_trim(
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p_alts[0], p_weights[0],
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&lower_rid, &upper_rid,
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&lower_tag, &upper_tag);
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lfsr_rbyd_p_pop(p_alts, p_weights, p_jumps);
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// trim red bounds
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} else {
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lfsr_tag_trim(
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p_alts[0], p_weights[0],
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&lower_rid, &upper_rid,
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&lower_tag, &upper_tag);
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}
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}
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// unreachable?
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if (lfsr_tag_unreachable(
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// trim alts from our current bounds
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lfsr_tag_trim2(
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alt, weight,
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lower_rid, upper_rid,
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lower_tag, upper_tag)) {
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// red unreachable? prune
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if (lfsr_tag_isred(p_alts[0])) {
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printf("%04x->%04x: brprune 0x%x w%d\n",
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branch,
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rbyd->eoff,
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alt,
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weight);
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lfsr_tag_trim(
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alt, weight,
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&lower_rid, &upper_rid,
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&lower_tag, &upper_tag);
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p_alts[0] &= ~LFSR_TAG_R;
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y_branch = branch;
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branch = branch_;
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continue;
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p_alts[0], p_weights[0],
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&lower_rid, &upper_rid,
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&lower_tag, &upper_tag);
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// black unreachable? collapse to alt-nevers, otherwise
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// we risk breaking the coloring of our tree
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} else {
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printf("%04x->%04x: bprune 0x%x w%d\n",
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branch,
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rbyd->eoff,
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alt,
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weight);
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lfsr_tag_trim(
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alt, weight,
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&lower_rid, &upper_rid,
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&lower_tag, &upper_tag);
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alt = LFSR_TAG_ALT(LFSR_TAG_LE, LFSR_TAG_B, 0);
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weight = 0;
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jump = 0;
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}
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// trim black bounds
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} else {
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lfsr_tag_trim(
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alt, weight,
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&lower_rid, &upper_rid,
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&lower_tag, &upper_tag);
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}
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// // trim alts from our current bounds
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// lfsr_tag_trim2(
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// alt, weight,
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// p_alts[0], p_weights[0],
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// &lower_rid, &upper_rid,
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// &lower_tag, &upper_tag);
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//
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// // keep track of last alt on diverged trunk to stitch the
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// // trunks together with
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// if ((d_state == LFSR_D_DIVERGEDLOWER
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