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Fixed delete issue with cut starting in a red edge

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Though this is a bit of an ugly fix...

Red edges mess everything up during deletion since we always need to
go down red edges in case we need to do a red flip. This puts our
algorithm into an awkward state.

It would be easier to do away with colors completely when we start
deleting (after all this branch of the tree _will_ be shrinking), but
this conflicts with the ultimate goal of deduplicate rbyd append.
This commit is contained in:
Christopher Haster
2022-12-31 02:03:47 -06:00
parent ca710b5a29
commit 1b6e1fdd33
2 changed files with 87 additions and 77 deletions
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lfs.c
+23 -13
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@@ -1568,9 +1568,9 @@ static int lfs_rbyd_append(lfs_t *lfs, lfs_rbyd_t *rbyd_,
// should've taken red alt? needs a flip
if (lt < 0 || gt < 0) {
LFS_ASSERT(lfs_rtag_isblack(alt));
LFS_ASSERT(p_alts[0]);
LFS_ASSERT(lfs_rtag_isred(p_alts[0]));
LFS_ASSERT(lfs_rtag_isblack(alt));
printf("rflip %s (%x,%x)\n",
lfs_rtag_isparallel(alt, p_alts[0]) ? "parallel" : "perpendicular",
@@ -1777,7 +1777,7 @@ static int lfs_rbyd_delete(lfs_t *lfs, lfs_rbyd_t *rbyd_,
// queue of pending alts we can emulate rotations with
lfs_rtag_t p_alts[3] = {0, 0, 0};
lfs_off_t p_jumps[3] = {0, 0, 0};
lfs_off_t graft = 0;
lfs_off_t graft = lower_branch;
// descend down tree, building alt pointers
while (true) {
@@ -1804,7 +1804,14 @@ static int lfs_rbyd_delete(lfs_t *lfs, lfs_rbyd_t *rbyd_,
if (!cut && lfs_rtag_follow(alt, lower_lt, lower_gt)
!= lfs_rtag_follow(alt, upper_lt, upper_gt)) {
printf("beginning cut\n");
printf("lower, upper = (%x, %x), (%x, %x)\n", lower_lt, lower_gt, upper_lt, upper_gt);
cut = true;
// TODO do we need this if we flip red alts early?
if (p_alts[0] && lfs_rtag_isred(p_alts[0])) {
upper_branch = graft;
lfs_rtag_untrim(p_alts[0], &upper_lt, &upper_gt);
}
}
// prune?
@@ -1847,7 +1854,7 @@ static int lfs_rbyd_delete(lfs_t *lfs, lfs_rbyd_t *rbyd_,
} else {
printf("ysplit nofollow\n");
LFS_ASSERT(graft != 0);
// LFS_ASSERT(graft != 0);
p_alts[0] = lfs_rtag_black(
lfs_rtag_merge(alt, p_alts[0]));
p_jumps[0] = graft;
@@ -1855,7 +1862,7 @@ static int lfs_rbyd_delete(lfs_t *lfs, lfs_rbyd_t *rbyd_,
lfs_rtag_trim(alt, &lt, &gt);
lfs_rbyd_p_red(p_alts, p_jumps);
graft = 0;
graft = branch;
branch = branch_;
goto next;
}
@@ -1863,13 +1870,12 @@ static int lfs_rbyd_delete(lfs_t *lfs, lfs_rbyd_t *rbyd_,
// should've taken red alt? needs a flip
if (lt < 0 || gt < 0) {
LFS_ASSERT(lfs_rtag_isblack(alt));
LFS_ASSERT(p_alts[0]);
LFS_ASSERT(lfs_rtag_isred(p_alts[0]));
printf("rflip %s (%x,%x)\n",
lfs_rtag_isparallel(alt, p_alts[0]) ? "parallel" : "perpendicular",
lt, gt);
LFS_ASSERT(p_alts[0]);
LFS_ASSERT(lfs_rtag_isred(p_alts[0]));
LFS_ASSERT(lfs_rtag_isblack(alt));
// if black alt would've been taken, it also needs a flip
if (lfs_rtag_isparallel(alt, p_alts[0])) {
@@ -1901,13 +1907,16 @@ static int lfs_rbyd_delete(lfs_t *lfs, lfs_rbyd_t *rbyd_,
// TODO can this be combined with prune? maybe not?
// cut?
if (cut && ((lower && lfs_rtag_isgt(alt))
|| (!lower && lfs_rtag_islt(alt)))) {
if (p_alts[0]) {
if (cut && lfs_rtag_isblack(alt)
&& ((lower && lfs_rtag_isgt(alt))
|| (!lower && lfs_rtag_islt(alt)))) {
if (p_alts[0] && lfs_rtag_isred(p_alts[0])) {
printf("bcut\n");
p_alts[0] = lfs_rtag_black(p_alts[0]);
if ((lower && lfs_rtag_isgt(alt))
|| (!lower && lfs_rtag_islt(alt))) {
printf("rcut\n");
lfs_rbyd_p_pop(p_alts, p_jumps);
}
}
@@ -1941,9 +1950,9 @@ static int lfs_rbyd_delete(lfs_t *lfs, lfs_rbyd_t *rbyd_,
}
// switch bounds we are following?
if (cut && lfs_rtag_isblack(alt) && !other_done) {
printf("switch bounds\n");
if (cut && p_alts[0] && lfs_rtag_isblack(p_alts[0]) && !other_done) {
lower = !lower;
printf("switch bounds -> %s\n", lower ? "lower" : "upper");
}
// found end of tree?
@@ -1985,6 +1994,7 @@ static int lfs_rbyd_delete(lfs_t *lfs, lfs_rbyd_t *rbyd_,
if (cut && !other_done) {
other_done = true;
lower = !lower;
printf("switch bounds -> %s\n", lower ? "lower" : "upper");
continue;
}