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libpgf: simple optimization in the implementation for heaps

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kr.angelov
2012-03-02 17:43:46 +00:00
parent 5983268552
commit 58b6bbd242
1 changed files with 19 additions and 24 deletions
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43
src/runtime/c/gu/seq.c
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@@ -164,34 +164,30 @@ gu_buf_freeze(GuBuf* buf, GuPool* pool)
}
static void
gu_heap_siftdown(GuBuf *buf, GuOrder *order, int startpos, int pos)
gu_heap_siftdown(GuBuf *buf, GuOrder *order,
const void *value, int startpos, int pos)
{
void *newitem = alloca(buf->elem_size);
memcpy(newitem, &buf->data[buf->elem_size * pos], buf->elem_size);
while (pos > startpos) {
int parentpos = (pos - 1) >> 1;
void *parent = &buf->data[buf->elem_size * parentpos];
if (order->compare(order, newitem, parent) < 0) {
memcpy(&buf->data[buf->elem_size * pos], parent, buf->elem_size);
pos = parentpos;
continue;
}
break;
if (order->compare(order, value, parent) >= 0)
break;
memcpy(&buf->data[buf->elem_size * pos], parent, buf->elem_size);
pos = parentpos;
}
memcpy(&buf->data[buf->elem_size * pos], newitem, buf->elem_size);
memcpy(&buf->data[buf->elem_size * pos], value, buf->elem_size);
}
static void
gu_heap_siftup(GuBuf *buf, GuOrder *order, int pos)
gu_heap_siftup(GuBuf *buf, GuOrder *order,
const void *value, int pos)
{
int startpos = pos;
int endpos = gu_buf_length(buf);
void *newitem = alloca(buf->elem_size);
memcpy(newitem, &buf->data[buf->elem_size * pos], buf->elem_size);
int childpos = 2*pos + 1;
while (childpos < endpos) {
int rightpos = childpos + 1;
@@ -208,15 +204,14 @@ gu_heap_siftup(GuBuf *buf, GuOrder *order, int pos)
childpos = 2*pos + 1;
}
memcpy(&buf->data[buf->elem_size * pos], newitem, buf->elem_size);
gu_heap_siftdown(buf, order, startpos, pos);
gu_heap_siftdown(buf, order, value, startpos, pos);
}
void
gu_buf_heap_push(GuBuf *buf, GuOrder *order, void *value)
{
memcpy(gu_buf_extend(buf), value, buf->elem_size);
gu_heap_siftdown(buf, order, 0, gu_buf_length(buf)-1);
gu_buf_extend(buf);
gu_heap_siftdown(buf, order, value, 0, gu_buf_length(buf)-1);
}
void
@@ -226,8 +221,7 @@ gu_buf_heap_pop(GuBuf *buf, GuOrder *order, void* data_out)
if (gu_buf_length(buf) > 0) {
memcpy(data_out, buf->data, buf->elem_size);
memcpy(buf->data, last, buf->elem_size);
gu_heap_siftup(buf, order, 0);
gu_heap_siftup(buf, order, last, 0);
} else {
memcpy(data_out, last, buf->elem_size);
}
@@ -239,17 +233,18 @@ gu_buf_heap_replace(GuBuf *buf, GuOrder *order, void *value, void *data_out)
gu_require(gu_buf_length(buf) > 0);
memcpy(data_out, buf->data, buf->elem_size);
memcpy(buf->data, value, buf->elem_size);
gu_heap_siftup(buf, order, 0);
gu_heap_siftup(buf, order, value, 0);
}
void
gu_buf_heapify(GuBuf *buf, GuOrder *order)
{
size_t middle = gu_buf_length(buf) / 2;
void *value = alloca(buf->elem_size);
for (size_t i = 0; i < middle; i++) {
gu_heap_siftup(buf, order, i);
memcpy(value, &buf->data[buf->elem_size * i], buf->elem_size);
gu_heap_siftup(buf, order, value, i);
}
}