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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 a4ed7a17f7
commit 79c7141973
1 changed files with 19 additions and 24 deletions
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41
src/runtime/c/gu/seq.c
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@@ -164,33 +164,29 @@ gu_buf_freeze(GuBuf* buf, GuPool* pool)
} }
static void 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) { while (pos > startpos) {
int parentpos = (pos - 1) >> 1; int parentpos = (pos - 1) >> 1;
void *parent = &buf->data[buf->elem_size * parentpos]; void *parent = &buf->data[buf->elem_size * parentpos];
if (order->compare(order, newitem, parent) < 0) { if (order->compare(order, value, parent) >= 0)
memcpy(&buf->data[buf->elem_size * pos], parent, buf->elem_size); break;
pos = parentpos;
continue; memcpy(&buf->data[buf->elem_size * pos], parent, buf->elem_size);
} pos = parentpos;
break;
} }
memcpy(&buf->data[buf->elem_size * pos], newitem, buf->elem_size); memcpy(&buf->data[buf->elem_size * pos], value, buf->elem_size);
} }
static void 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 startpos = pos;
int endpos = gu_buf_length(buf); 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; int childpos = 2*pos + 1;
while (childpos < endpos) { while (childpos < endpos) {
@@ -208,15 +204,14 @@ gu_heap_siftup(GuBuf *buf, GuOrder *order, int pos)
childpos = 2*pos + 1; childpos = 2*pos + 1;
} }
memcpy(&buf->data[buf->elem_size * pos], newitem, buf->elem_size); gu_heap_siftdown(buf, order, value, startpos, pos);
gu_heap_siftdown(buf, order, startpos, pos);
} }
void void
gu_buf_heap_push(GuBuf *buf, GuOrder *order, void *value) gu_buf_heap_push(GuBuf *buf, GuOrder *order, void *value)
{ {
memcpy(gu_buf_extend(buf), value, buf->elem_size); gu_buf_extend(buf);
gu_heap_siftdown(buf, order, 0, gu_buf_length(buf)-1); gu_heap_siftdown(buf, order, value, 0, gu_buf_length(buf)-1);
} }
void void
@@ -226,8 +221,7 @@ gu_buf_heap_pop(GuBuf *buf, GuOrder *order, void* data_out)
if (gu_buf_length(buf) > 0) { if (gu_buf_length(buf) > 0) {
memcpy(data_out, buf->data, buf->elem_size); memcpy(data_out, buf->data, buf->elem_size);
memcpy(buf->data, last, buf->elem_size); gu_heap_siftup(buf, order, last, 0);
gu_heap_siftup(buf, order, 0);
} else { } else {
memcpy(data_out, last, buf->elem_size); 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); gu_require(gu_buf_length(buf) > 0);
memcpy(data_out, buf->data, buf->elem_size); memcpy(data_out, buf->data, buf->elem_size);
memcpy(buf->data, value, buf->elem_size); gu_heap_siftup(buf, order, value, 0);
gu_heap_siftup(buf, order, 0);
} }
void void
gu_buf_heapify(GuBuf *buf, GuOrder *order) gu_buf_heapify(GuBuf *buf, GuOrder *order)
{ {
size_t middle = gu_buf_length(buf) / 2; size_t middle = gu_buf_length(buf) / 2;
void *value = alloca(buf->elem_size);
for (size_t i = 0; i < middle; i++) { 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);
} }
} }