rbyd: Progress towards rbyd balance, separated y-pruning, hacky goto
The main idea here is we need to unconditionally descend down red/yellow alts to check if they're post-split yellow nodes before pruning, since yellow nodes should be recolored to maintain the color balance of our tree. To make this work: - Added separate y-pruning logic before our diverged logic, this starts to look a bit like previous incarnations of this function. - Our non-y-pruning logic is all now gated behind the if-diverging check, so we shouldn't be non-y-pruning at all unless we've diverged. It may be worth rewriting this to use the trimming logic directly, instead of reachability. - Moving non-y-pruning logic behind the if-diverging check ended up causing problems for the stitching node, which is still a bit of a special case. A hacky goto solves this for now at the risk of velociraptors... https://xkcd.com/292 It's hacky, but the goal right now is to just get something working. This may seem like a lot of changes for only a couple more tests passing, but progress is progress: test_rbyd+balance before: 306/385878 failed test_rbyd+balance after: 300/385878 failed (-2.0%) Code changes: code stack ctx before: 38528 2624 640 after: 38644 (+0.3%) 2624 (+0.0%) 640 (+0.0%)
This commit is contained in:
Christopher Haster
@@ -3619,6 +3619,52 @@ trunk:;
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LFS_SWAP(lfs_size_t, &jump, &branch_);
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}
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// TODO redoc?
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// prune?
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if (lfsr_tag_isred(p[0].alt)) {
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// prune unreachable red alts
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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 1
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if (lfsr_tag_unreachable(
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p[0].alt, p[0].weight,
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lower_rid, upper_rid,
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lower_tag, upper_tag)) {
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LFS_DEBUG("%04x->%04x: yprune",
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branch, lfsr_rbyd_eoff(rbyd));
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alt &= ~LFSR_TAG_R;
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lfsr_rbyd_p_pop(p);
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// prune other unreachable alts
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// <b >b
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// .-'| .-'|
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// <y | | <b
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// .-------'| | .-----------|-'|
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// | <r | => | | |
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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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} else if (lfsr_tag_unreachable2(
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alt, weight,
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p[0].alt, p[0].weight,
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lower_rid, upper_rid,
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lower_tag, upper_tag)) {
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LFS_DEBUG("%04x->%04x: rprune",
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branch, lfsr_rbyd_eoff(rbyd));
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alt = p[0].alt & ~LFSR_TAG_R;
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weight = p[0].weight;
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jump = p[0].jump;
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lfsr_rbyd_p_pop(p);
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}
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}
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// TODO need this? does this ever get triggered?
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// both diverging? collapse
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// <r >b
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@@ -3638,7 +3684,7 @@ trunk:;
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lower_rid, upper_rid,
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a_rid, a_tag,
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b_rid, b_tag);
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if (diverging && diverging_red) {
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if (!diverged && diverging && diverging_red) {
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LFS_DEBUG("%04x->%04x: both diverging",
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branch, lfsr_rbyd_eoff(rbyd));
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LFS_ASSERT(a_rid < b_rid || a_tag < b_tag);
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@@ -3705,7 +3751,7 @@ trunk:;
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&& (diverging || diverging_red)) {
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LFS_DEBUG("%04x->%04x: diverging",
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branch, lfsr_rbyd_eoff(rbyd));
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if (lfsr_tag_isred(p[0].alt)) {
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if (lfsr_tag_isred(alt)) {
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LFS_DEBUG("%04x->%04x: wouldnt've diverged",
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branch, lfsr_rbyd_eoff(rbyd));
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}
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@@ -3758,6 +3804,8 @@ trunk:;
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// TODO should we assert we're only diverging here?
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// not diverging_red?
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// TODO can this be red? can we assert it's black?
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// TODO is this uh, how much of this is already in
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// the diverging alt?
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@@ -3809,110 +3857,132 @@ trunk:;
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// // continue to next alt
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// branch = branch_;
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// continue;
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goto maybetrim;
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}
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// diverged?
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// : :
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// <b => nb
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// .-'| .--'
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// 3 4 3 4 x
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} else if (diverged && diverging) {
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LFS_DEBUG("%04x->%04x: div pruning",
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branch, lfsr_rbyd_eoff(rbyd));
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// trim so alt is pruned
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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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weight = 0;
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}
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} else if (diverged) {
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// diverging = lfsr_tag_diverging2(
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// alt, weight,
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// p[0].alt, p[0].weight,
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// lower_rid, upper_rid,
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// a_rid, a_tag,
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// b_rid, b_tag);
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// diverging_red = lfsr_tag_isred(p[0].alt)
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// && lfsr_tag_diverging(
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// p[0].alt, p[0].weight,
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// lower_rid, upper_rid,
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// a_rid, a_tag,
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// b_rid, b_tag);
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// if (diverging_red) {
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// LFS_DEBUG("%04x->%04x: div r pruning",
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// branch, lfsr_rbyd_eoff(rbyd));
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// // trim so alt is pruned
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// lfsr_tag_trim(
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// p[0].alt, p[0].weight,
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// &lower_rid, &upper_rid,
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// &lower_tag, &upper_tag);
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// p[0].weight = 0;
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//
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// lfsr_rbyd_p_pop(p);
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//
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// // TODO prune? (trim?)
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// }
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// prune?
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//
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// note if only yellow pruning this could be much simpler
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// prune unreachable red alts
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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 1
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if (lfsr_tag_isred(p[0].alt)
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&& lfsr_tag_unreachable(
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p[0].alt, p[0].weight,
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lower_rid, upper_rid,
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lower_tag, upper_tag)) {
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LFS_DEBUG("%04x->%04x: yprune",
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branch, lfsr_rbyd_eoff(rbyd));
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alt &= ~LFSR_TAG_R;
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lfsr_rbyd_p_pop(p);
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}
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// prune other unreachable alts
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// <b >b
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// .-'| .-'|
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// <y | | <b
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// .-------'| | .-----------|-'|
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// | <r | => | | |
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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_unreachable2(
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diverging = lfsr_tag_diverging2(
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alt, weight,
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p[0].alt, p[0].weight,
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lower_rid, upper_rid,
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lower_tag, upper_tag)) {
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// prune unreachable recolorable alts
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// : :
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// <r => <b
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// .----'| .-------'|
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// | <b | |
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// | .-'| | .-----'
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// 1 2 3 1 2 3 x
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if (lfsr_tag_isred(p[0].alt)) {
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alt = p[0].alt & ~LFSR_TAG_R;
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weight = p[0].weight;
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jump = p[0].jump;
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lfsr_rbyd_p_pop(p);
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a_rid, a_tag,
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b_rid, b_tag);
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if (diverging) {
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// && (!lfsr_tag_isred(alt)
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// || lfsr_tag_isred(p[0].alt))) {
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LFS_DEBUG("%04x->%04x: div b pruning",
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branch, lfsr_rbyd_eoff(rbyd));
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// trim so alt is pruned
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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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weight = 0;
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// TODO redoc
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// prune unreachable root alts and red alts
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// : :
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// <r => <b
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// .----'| .----'|
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// | <b | |
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// | .-'| | .--'
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// 3 4 5 3 4 5 x
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} else if (!p[0].alt) { //|| lfsr_tag_isred(alt)) {
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branch = branch_;
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continue;
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maybetrim:;
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// prune other unreachable alts
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// <b >b
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// .-'| .-'|
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// <y | | <b
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// .-------'| | .-----------|-'|
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// | <r | => | | |
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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_unreachable2(
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alt, weight,
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p[0].alt, p[0].weight,
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lower_rid, upper_rid,
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lower_tag, upper_tag)) {
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// prune unreachable recolorable alts
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// : :
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// <r => <b
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// .----'| .-------'|
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// | <b | |
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// | .-'| | .-----'
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// 1 2 3 1 2 3 x
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if (lfsr_tag_isred(p[0].alt)) {
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LFS_DEBUG("%04x->%04x: rprune",
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branch, lfsr_rbyd_eoff(rbyd));
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alt = p[0].alt & ~LFSR_TAG_R;
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weight = p[0].weight;
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jump = p[0].jump;
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lfsr_rbyd_p_pop(p);
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// mark unreachable non-root black alts as unreachable,
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// we can't prune these or we risk breaking the color
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// balance of our tree, but if we push a red up later we
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// can get rid of them
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// : :
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// <b => nb
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// .-'| .--'
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// 3 4 3 4 x
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} else {
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alt = LFSR_TAG_ALT(
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LFSR_TAG_B,
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LFSR_TAG_LE,
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(diverged && !(a_rid < b_rid || a_tag < b_tag))
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? d_tag
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: lower_tag);
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// TODO hmmmmm?
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LFS_ASSERT(weight == 0);
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//weight = 0;
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// we don't need to, but setting jump=0 asserts this
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// alt is unreachable while also minimizing the the
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// encoding
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jump = 0;
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// TODO redoc
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// TODO does this ever get hit?
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// prune unreachable root alts and red alts
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// : :
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// <r => <b
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// .----'| .----'|
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// | <b | |
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// | .-'| | .--'
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// 3 4 5 3 4 5 x
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} else if (!p[0].alt) { //|| lfsr_tag_isred(alt)) {
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LFS_DEBUG("%04x->%04x: zprune",
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branch, lfsr_rbyd_eoff(rbyd));
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branch = branch_;
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continue;
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// mark unreachable non-root black alts as unreachable,
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// we can't prune these or we risk breaking the color
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// balance of our tree, but if we push a red up later we
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// can get rid of them
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// : :
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// <b => nb
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// .-'| .--'
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// 3 4 3 4 x
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} else if (!lfsr_tag_isred(alt)) {
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LFS_DEBUG("%04x->%04x: bprune",
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branch, lfsr_rbyd_eoff(rbyd));
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alt = LFSR_TAG_ALT(
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LFSR_TAG_B,
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LFSR_TAG_LE,
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(diverged && !(a_rid < b_rid || a_tag < b_tag))
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? d_tag
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: lower_tag);
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// TODO hmmmmm?
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LFS_ASSERT(weight == 0);
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//weight = 0;
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// we don't need to, but setting jump=0 asserts this
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// alt is unreachable while also minimizing the the
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// encoding
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jump = 0;
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}
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}
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}
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}
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