revset: add depth limit to descendants() (issue5374)
This is naive implementation using two-pass scanning. Tracking descendants
isn't an easy problem if both start and stop depths are specified. It's
impractical to remember all possible depths of each node while scanning from
roots to descendants because the number of depths explodes. Instead, we could
cache (min, max) depths as a good approximation and track ancestors back when
needed, but that's likely to have off-by-one bug.
Since this implementation appears not significantly slower, and is quite
straightforward, I think it's good enough for practical use cases. The time
and space complexity is O(n) ish.
revisions:
0) 1-pass scanning with (min, max)-depth cache (worst-case quadratic)
1) 2-pass scanning (this version)
repository:
mozilla-central
# descendants(0) (for reference)
*) 0.430353
# descendants(0, depth=1000)
0) 0.264889
1) 0.398289
# descendants(limit(tip:0, 1, offset=10000), depth=1000)
0) 0.025478
1) 0.029099
# descendants(0, depth=2000, startdepth=1000)
0) painfully slow (due to quadratic backtracking of ancestors)
1) 1.531138
HG = $(CURDIR)/../../hg
TARGET = chg
SRCS = chg.c hgclient.c procutil.c util.c
OBJS = $(SRCS:.c=.o)
CFLAGS ?= -O2 -Wall -Wextra -pedantic -g
CPPFLAGS ?= -D_FORTIFY_SOURCE=2
override CFLAGS += -std=gnu99
ifdef HGPATH
override CPPFLAGS += -DHGPATH=\"$(HGPATH)\"
endif
DESTDIR =
PREFIX = /usr/local
MANDIR = $(PREFIX)/share/man/man1
CHGSOCKDIR = /tmp/chg$(shell id -u)
CHGSOCKNAME = $(CHGSOCKDIR)/server
.PHONY: all
all: $(TARGET)
$(TARGET): $(OBJS)
$(CC) $(LDFLAGS) -o $@ $(OBJS)
chg.o: hgclient.h procutil.h util.h
hgclient.o: hgclient.h procutil.h util.h
procutil.o: procutil.h util.h
util.o: util.h
.PHONY: install
install: $(TARGET)
install -d $(DESTDIR)$(PREFIX)/bin
install -m 755 $(TARGET) $(DESTDIR)$(PREFIX)/bin
install -d $(DESTDIR)$(MANDIR)
install -m 644 chg.1 $(DESTDIR)$(MANDIR)
.PHONY: serve
serve:
[ -d $(CHGSOCKDIR) ] || ( umask 077; mkdir $(CHGSOCKDIR) )
$(HG) serve --cwd / --cmdserver chgunix \
--address $(CHGSOCKNAME) \
--config cmdserver.log=/dev/stderr
.PHONY: clean
clean:
$(RM) $(OBJS)
.PHONY: distclean
distclean:
$(RM) $(OBJS) $(TARGET)