Taylor Blau <me@xxxxxxxxxxxx> writes:
> From: Derrick Stolee <dstolee@xxxxxxxxxxxxx>
>
> 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@xxxxxxxxxxxxx>
> Signed-off-by: Taylor Blau <me@xxxxxxxxxxxx>
> ---
> 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);
