| Message ID | 4840c64c51d65ea7bf1ebe03cad4588267db0207.1605649533.git.me@ttaylorr.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | pack-bitmap: bitmap generation improvements | expand |
Taylor Blau <me@ttaylorr.com> writes: > From: Derrick Stolee <dstolee@microsoft.com> > > The bitmap_diff_nonzero() checks if the 'self' bitmap contains any bits > that are not on in the 'other' bitmap. In other words, it yields false if and only if self is a subset of other? I have to say that "diff_nonzero" is much less helpful than words like "subset" or "superset" when I try to imagine what the function would compute. If this were widely used helper function, I may insist on flipping the polarity and call it bitmap_is_subset(), but I dunno... > Also, delete the declaration of bitmap_is_subset() as it is not used or > implemented. ;-) > Signed-off-by: Derrick Stolee <dstolee@microsoft.com> > Signed-off-by: Taylor Blau <me@ttaylorr.com> > --- > ewah/bitmap.c | 24 ++++++++++++++++++++++++ > ewah/ewok.h | 2 +- > 2 files changed, 25 insertions(+), 1 deletion(-) > > diff --git a/ewah/bitmap.c b/ewah/bitmap.c > index eb7e2539be..e2ebeac0e5 100644 > --- a/ewah/bitmap.c > +++ b/ewah/bitmap.c > @@ -200,6 +200,30 @@ int bitmap_equals(struct bitmap *self, struct bitmap *other) > return 1; > } > > +int bitmap_diff_nonzero(struct bitmap *self, struct bitmap *other) > +{ > + struct bitmap *small; It is not wrong per-se, but s/small/smaller/ would be more natural? I actually think it would be easier to follow the logic to replace this pointer with size_t common_size; Then the code becomes if (self->word_alloc < other->word_alloc) common_size = self->word_alloc; else { common_size = other->word_alloc; for (i = common_size; i < self->word_alloc; i++) if (self->words[i]) ... self is *not* subset ... } for (i = 0; i < common_size; i++) if (self->words[i] & ~other->words[i])) ... self is *not* subset ... > + size_t i; > + > + if (self->word_alloc < other->word_alloc) { > + small = self; > + } else { > + small = other; > + > + for (i = other->word_alloc; i < self->word_alloc; i++) { > + if (self->words[i] != 0) > + return 1; > + } > + } > + > + for (i = 0; i < small->word_alloc; i++) { > + if ((self->words[i] & ~other->words[i])) > + return 1; > + } > + > + return 0; > +} > + > void bitmap_reset(struct bitmap *bitmap) > { > memset(bitmap->words, 0x0, bitmap->word_alloc * sizeof(eword_t)); > diff --git a/ewah/ewok.h b/ewah/ewok.h > index 1fc555e672..156c71d06d 100644 > --- a/ewah/ewok.h > +++ b/ewah/ewok.h > @@ -180,7 +180,7 @@ int bitmap_get(struct bitmap *self, size_t pos); > void bitmap_reset(struct bitmap *self); > void bitmap_free(struct bitmap *self); > int bitmap_equals(struct bitmap *self, struct bitmap *other); > -int bitmap_is_subset(struct bitmap *self, struct bitmap *super); > +int bitmap_diff_nonzero(struct bitmap *self, struct bitmap *other); > > struct ewah_bitmap * bitmap_to_ewah(struct bitmap *bitmap); > struct bitmap *ewah_to_bitmap(struct ewah_bitmap *ewah);
On Sun, Nov 22, 2020 at 02:01:21PM -0800, Junio C Hamano wrote: > I actually think it would be easier to follow the logic to replace > this pointer with > > size_t common_size; > [ ... ] Yep, much clearer indeed. Thanks. Taylor
diff --git a/ewah/bitmap.c b/ewah/bitmap.c index eb7e2539be..e2ebeac0e5 100644 --- a/ewah/bitmap.c +++ b/ewah/bitmap.c @@ -200,6 +200,30 @@ int bitmap_equals(struct bitmap *self, struct bitmap *other) return 1; } +int bitmap_diff_nonzero(struct bitmap *self, struct bitmap *other) +{ + struct bitmap *small; + size_t i; + + if (self->word_alloc < other->word_alloc) { + small = self; + } else { + small = other; + + for (i = other->word_alloc; i < self->word_alloc; i++) { + if (self->words[i] != 0) + return 1; + } + } + + for (i = 0; i < small->word_alloc; i++) { + if ((self->words[i] & ~other->words[i])) + return 1; + } + + return 0; +} + void bitmap_reset(struct bitmap *bitmap) { memset(bitmap->words, 0x0, bitmap->word_alloc * sizeof(eword_t)); diff --git a/ewah/ewok.h b/ewah/ewok.h index 1fc555e672..156c71d06d 100644 --- a/ewah/ewok.h +++ b/ewah/ewok.h @@ -180,7 +180,7 @@ int bitmap_get(struct bitmap *self, size_t pos); void bitmap_reset(struct bitmap *self); void bitmap_free(struct bitmap *self); int bitmap_equals(struct bitmap *self, struct bitmap *other); -int bitmap_is_subset(struct bitmap *self, struct bitmap *super); +int bitmap_diff_nonzero(struct bitmap *self, struct bitmap *other); struct ewah_bitmap * bitmap_to_ewah(struct bitmap *bitmap); struct bitmap *ewah_to_bitmap(struct ewah_bitmap *ewah);