void HashTest::test_performance()
{
const int ITERATION_COUNT = 1000000;
{
Hash hf;
clock_t t = clock();
for(int i = 0; i < ITERATION_COUNT; ++i)
{
Id<16> id(true);
hf.AddData(id.ConstData(), id.Size);
GUINT32 hash = hf.Final();
GUTIL_UNUSED(hash);
}
clock_t e = clock();
qDebug("Number of ticks to do %d hashes was: %d", ITERATION_COUNT, (int)(e - t));
}
{
std::hash<string> hf;
clock_t t = clock();
for(int i = 0; i < ITERATION_COUNT; ++i)
{
Id<16> id(true);
string s((char const *)id.ConstData(), id.Size);
GUINT32 hash = hf(s);
GUTIL_UNUSED(hash);
}
clock_t e = clock();
qDebug("Number of ticks to do %d standard hashes was: %d", ITERATION_COUNT, (int)(e - t));
}
}
void HashTest::test_collisions()
{
// Do a collision check. It should be practically impossible to get a collision
double my_avg = 0;
const int ITERATION_COUNT = 25;
for(int i = 0; i < ITERATION_COUNT; ++i)
{
//qDebug("Iteration %d", i);
set<GUINT32> hashes;
GUINT32 cnt = 0;
bool collision = false;
Hash hf;
forever{
cnt++;
Id<16> id(true);
hf.AddData(id.ConstData(), id.Size);
GUINT32 hash = hf.Final();
collision = hashes.find(hash) != hashes.end();
if(!collision)
hashes.insert(hash);
else
break;
}
//qDebug(QString("Did %1 hashes before a collision").arg(cnt).toAscii());
//QVERIFY(cnt > 10000);
my_avg += cnt;
}
my_avg /= ITERATION_COUNT;
qDebug("My average number of hashes before collision was: %f", my_avg);
QVERIFY(my_avg > 50000);
// Compare our results with the standard hash
double their_avg = 0;
for(int i = 0; i < ITERATION_COUNT; ++i)
{
set<GUINT32> hashes;
GUINT32 cnt = 0;
bool collision = false;
std::hash<string> sh;
forever{
cnt++;
Id<16> id(true);
string s((char const *)id.ConstData(), id.Size);
GUINT32 hash = sh(s);
collision = hashes.find(hash) != hashes.end();
if(!collision)
hashes.insert(hash);
else
break;
}
their_avg += cnt;
//qDebug(QString("Standard hash did %1 hashes before a collision").arg(cnt).toAscii());
}
their_avg /= ITERATION_COUNT;
qDebug("The average number of standard hashes before collision was: %f", their_avg);
}
void HashTest::test_basics()
{
Hash h;
qDebug(QString("The hash object is %1 bytes large").arg(sizeof(h)).toAscii());
QVERIFY(4 == h.Size);
QVERIFY(Hash::Size == h.Size);
// The null hash is 0
QVERIFY(h.Final() == 0);
QVERIFY(Hash::ComputeHash(NULL, 0) == 0);
{
// Make sure hashes of all single bytes are unique
set<GUINT32> hashes;
for(int i = 0; i < 0x100; ++i){
byte tmp = i;
GUINT32 hash = Hash::ComputeHash(&tmp, 1);
QVERIFY(hashes.find(hash) == hashes.end());
hashes.insert(hash);
}
// Make sure hashing the same input gives us the same output
for(int i = 0; i < 0x100; ++i){
byte tmp = i;
GUINT32 hash = Hash::ComputeHash(&tmp, 1);
QVERIFY(hashes.find(hash) != hashes.end());
}
}
// Hashes one way are not the same as hashes the other way
{
set<GUINT32> hashes;
for(byte c = 'a'; c <= 'z'; ++c){
for(byte c2 = c + 1; c2 <= 'z'; ++c2){
h.AddData(&c, 1);
h.AddData(&c2, 1);
GUINT32 hash1 = h.Final();
h.AddData(&c2, 1);
h.AddData(&c, 1);
GUINT32 hash2 = h.Final();
QVERIFY(hash1 != hash2);
QVERIFY(hashes.find(hash1) == hashes.end());
QVERIFY(hashes.find(hash2) == hashes.end());
hashes.insert(hash1);
hashes.insert(hash2);
}
}
}
// Hashes of repeat characters don't repeat hashes
{
set<GUINT32> hashes;
for(int i = 1; i < 10000; i++){
String s('a', i);
GUINT32 hash = Hash::ComputeHash((byte const *)s.ConstData(), i);
QVERIFY2(hashes.find(hash) == hashes.end(), QString("%1: %2").arg(i).arg(hash, 8, 16).toAscii());
hashes.insert(hash);
}
}
}