lix/table/aterm-map.cc

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#include <string>
#include <iostream>
#include <assert.h>
#include <math.h>
#include <aterm2.h>
using namespace std;
class ATermMap
{
private:
struct KeyValue
{
ATerm key;
ATerm value;
};
/* Hash table for the map. We use open addressing, i.e., all
key/value pairs are stored directly in the table, and there are
no pointers. Collisions are resolved through probing. */
KeyValue * hashTable;
/* Current size of the hash table. */
unsigned int size;
/* Number of elements in the hash table. */
unsigned int count;
/* Maximum number of elements in the hash table. If `count'
exceeds this number, the hash table is expanded. */
unsigned int maxCount;
public:
/* Create a map. `expectedCount' is the number of elements the
map is expected to hold. */
ATermMap(unsigned int expectedCount);
ATermMap(const ATermMap & map);
~ATermMap();
ATermMap & operator = (const ATermMap & map);
void set(ATerm key, ATerm value);
ATerm get(ATerm key) const;
void remove(ATerm key);
private:
void init(unsigned int expectedCount);
void free();
void resizeTable(unsigned int expectedCount);
void copy(KeyValue * elements, unsigned int size);
inline unsigned int hash1(ATerm key) const;
inline unsigned int hash2(ATerm key) const;
};
ATermMap::ATermMap(unsigned int expectedCount)
{
init(expectedCount * 10 / 9); /* slight adjustment */
}
ATermMap::ATermMap(const ATermMap & map)
{
init(map.maxCount);
copy(map.hashTable, map.size);
}
ATermMap & ATermMap::operator = (const ATermMap & map)
{
if (this == &map) return *this;
free();
init(map.maxCount);
copy(map.hashTable, map.size);
return *this;
}
ATermMap::~ATermMap()
{
free();
}
void ATermMap::init(unsigned int expectedCount)
{
assert(sizeof(ATerm) * 2 == sizeof(KeyValue));
size = 0;
count = 0;
maxCount = 0;
hashTable = 0;
resizeTable(expectedCount);
}
void ATermMap::free()
{
if (hashTable) {
ATunprotectArray((ATerm *) hashTable);
::free(hashTable);
hashTable = 0;
}
}
static unsigned int roundToPowerOf2(unsigned int x)
{
x--;
x |= x >> 1; x |= x >> 2; x |= x >> 4; x |= x >> 8; x |= x >> 16;
x++;
return x;
}
static const unsigned int maxLoadFactor = /* 1 / */ 3;
static unsigned int nrResizes = 0;
void ATermMap::resizeTable(unsigned int expectedCount)
{
if (expectedCount == 0) expectedCount = 1;
// cout << maxCount << " -> " << expectedCount << endl;
// cout << maxCount << " " << size << endl;
// cout << (double) size / maxCount << endl;
unsigned int oldSize = size;
KeyValue * oldHashTable = hashTable;
maxCount = expectedCount;
size = roundToPowerOf2(maxCount * maxLoadFactor);
hashTable = (KeyValue *) calloc(sizeof(KeyValue), size);
ATprotectArray((ATerm *) hashTable, size * 2);
// cout << size << endl;
/* Re-hash the elements in the old table. */
if (oldSize != 0) {
count = 0;
copy(oldHashTable, oldSize);
ATunprotectArray((ATerm *) oldHashTable);
::free(oldHashTable);
nrResizes++;
}
}
void ATermMap::copy(KeyValue * elements, unsigned int size)
{
for (unsigned int i = 0; i < size; ++i)
if (elements[i].value) /* i.e., non-empty, non-deleted element */
set(elements[i].key, elements[i].value);
}
static const unsigned int shift = 16;
static const unsigned int knuth = (unsigned int) (0.6180339887 * (1 << shift));
unsigned int ATermMap::hash1(ATerm key) const
{
/* Don't care about the least significant bits of the ATerm
pointer since they're always 0. */
unsigned int key2 = ((unsigned int) key) >> 2;
/* Approximately equal to:
double d = key2 * 0.6180339887;
unsigned int h = (int) (size * (d - floor(d)));
*/
unsigned int h = (size * ((key2 * knuth) & ((1 << shift) - 1))) >> shift;
return h;
}
unsigned int ATermMap::hash2(ATerm key) const
{
unsigned int key2 = ((unsigned int) key) >> 2;
/* Note: the result must be relatively prime to `size' (which is a
power of 2), so we make sure that the result is always odd. */
unsigned int h = ((key2 * 134217689) & (size - 1)) | 1;
return h;
}
static unsigned int nrItemsSet = 0;
static unsigned int nrSetProbes = 0;
void ATermMap::set(ATerm key, ATerm value)
{
if (count == maxCount) resizeTable(size * 2 / maxLoadFactor);
nrItemsSet++;
for (unsigned int i = 0, h = hash1(key); i < size;
++i, h = (h + hash2(key)) & (size - 1))
{
// assert(h < size);
nrSetProbes++;
/* Note: to see whether a slot is free, we check
hashTable[h].value, not hashTable[h].key, since we use
value == 0 to mark deleted slots. */
if (hashTable[h].value == 0 || hashTable[h].key == key) {
hashTable[h].key = key;
hashTable[h].value = value;
count++;
return;
}
}
abort();
}
static unsigned int nrItemsGet = 0;
static unsigned int nrGetProbes = 0;
ATerm ATermMap::get(ATerm key) const
{
nrItemsGet++;
for (unsigned int i = 0, h = hash1(key); i < size;
++i, h = (h + hash2(key)) & (size - 1))
{
nrGetProbes++;
if (hashTable[h].key == 0) return 0;
if (hashTable[h].key == key) return hashTable[h].value;
}
return 0;
}
void ATermMap::remove(ATerm key)
{
for (unsigned int i = 0, h = hash1(key); i < size;
++i, h = (h + hash2(key)) & (size - 1))
{
if (hashTable[h].key == 0) return;
if (hashTable[h].key == key) {
hashTable[h].value = 0;
return;
}
}
}
int main(int argc, char * * argv)
{
ATerm bottomOfStack;
ATinit(argc, argv, &bottomOfStack);
/* Make test terms. */
int nrTestTerms = 100000;
ATerm testTerms[nrTestTerms];
for (int i = 0; i < nrTestTerms; ++i) {
char name[10];
sprintf(name, "%d", (int) random() % 37);
int arity = i == 0 ? 0 : (random() % 37);
ATerm kids[arity];
for (int j = 0; j < arity; ++j)
kids[j] = testTerms[random() % i];
testTerms[i] = (ATerm) ATmakeApplArray(ATmakeAFun(name, arity, ATfalse), kids);
// ATwriteToSharedTextFile(testTerms[i], stdout);
// printf("\n");
}
cout << "testing...\n";
#define someTerm() (testTerms[(int) random() % nrTestTerms])
for (int test = 0; test < 100000; ++test) {
// cerr << test << endl;
unsigned int n = 300;
ATermMap map(300);
ATerm keys[n], values[n];
for (unsigned int i = 0; i < n; ++i) {
keys[i] = someTerm();
values[i] = someTerm();
map.set(keys[i], values[i]);
// cerr << "INSERT: " << keys[i] << " " << values[i] << endl;
}
values[n - 1] = 0;
map.remove(keys[n - 1]);
for (unsigned int i = 0; i < n; ++i) {
if (map.get(keys[i]) != values[i]) {
for (unsigned int j = i + 1; j < n; ++j)
if (keys[i] == keys[j]) goto x;
cerr << "MISMATCH: " << keys[i] << " " << values[i] << " " << map.get(keys[i]) << " " << i << endl;
abort();
x: ;
}
}
for (unsigned int i = 0; i < 100; ++i)
map.get(someTerm());
}
cout << "RESIZES: " << nrResizes << endl;
cout << "SET: "
<< nrItemsSet << " "
<< nrSetProbes << " "
<< (double) nrSetProbes / nrItemsSet << endl;
cout << "GET: "
<< nrItemsGet << " "
<< nrGetProbes << " "
<< (double) nrGetProbes / nrItemsGet << endl;
}