Open-Harbor/osrm-backend
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases 3 Wiki Activity

Cut down memory usage for tables in XORFastHash by factor of four

Browse Source 
`pow(2, 16)` is not `2 << 16` but rather `1 << 16`.

With this change we cut memory usage in half for the XORFastHash's two
tables. Adapts XORFastHashStorage, memory usage reduction by factor two.
This commit is contained in:
Daniel J. Hofmann 2016-01-21 16:30:46 +01:00
parent 60ef6070b0
commit 1417d43430
2 changed files with 14 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
include/util/xor_fast_hash.hpp
View File

@ -37,8 +37,8 @@ namespace util
*/
class XORFastHash
{ // 65k entries
std::array<std::uint16_t, (2u << 16u)> table1;
std::array<std::uint16_t, (2u << 16u)> table2;
std::array<std::uint16_t, (1u << 16u)> table1;
std::array<std::uint16_t, (1u << 16u)> table2;
public:
XORFastHash()

18
include/util/xor_fast_hash_storage.hpp
View File

@ -34,29 +34,35 @@ template <typename NodeID, typename Key> class XORFastHashStorage
XORFastHashStorage() = delete;
explicit XORFastHashStorage(size_t) : positions(2 << 16), current_timestamp(0) {}
explicit XORFastHashStorage(size_t) : positions(1u << 16u), current_timestamp(0) {}
HashCell &operator[](const NodeID node)
{
unsigned short position = fast_hasher(node);
std::uint16_t position = fast_hasher(node);
while ((positions[position].time == current_timestamp) && (positions[position].id != node))
{
++position %= (2 << 16);
++position %= (1u << 16u);
}
positions[position].time = current_timestamp;
positions[position].id = node;
BOOST_ASSERT(position < positions.size());
return positions[position];
}
// peek into table, get key for node, think of it as a read-only operator[]
Key peek_index(const NodeID node) const
{
unsigned short position = fast_hasher(node);
std::uint16_t position = fast_hasher(node);
while ((positions[position].time == current_timestamp) && (positions[position].id != node))
{
++position %= (2 << 16);
++position %= (1u << 16u);
}
BOOST_ASSERT(position < positions.size());
return positions[position].key;
}
@ -66,7 +72,7 @@ template <typename NodeID, typename Key> class XORFastHashStorage
if (std::numeric_limits<unsigned>::max() == current_timestamp)
{
positions.clear();
positions.resize(2 << 16);
positions.resize(1u << 16u);
}
}