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Further fixed hash function #3

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Further fixed hash function #3

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14 changes: 7 additions & 7 deletions count_min_sketch.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -45,9 +45,9 @@ CountMinSketch::CountMinSketch(float ep, float gamm) {
}
// initialize d pairwise independent hashes
srand(time(NULL));
hashes = new int* [d];
hashes = new unsigned long* [d];
for (i = 0; i < d; i++) {
hashes[i] = new int[2];
hashes[i] = new unsigned long[2];
genajbj(hashes, i);
}
}
Expand Down Expand Up @@ -79,7 +79,7 @@ void CountMinSketch::update(int item, int c) {
total = total + c;
unsigned int hashval = 0;
for (unsigned int j = 0; j < d; j++) {
hashval = ((long)hashes[j][0]*item+hashes[j][1])%LONG_PRIME%w;
hashval = (hashes[j][0]*item+hashes[j][1])%LONG_PRIME%w;
C[j][hashval] = C[j][hashval] + c;
}
}
Expand All @@ -95,7 +95,7 @@ unsigned int CountMinSketch::estimate(int item) {
int minval = numeric_limits<int>::max();
unsigned int hashval = 0;
for (unsigned int j = 0; j < d; j++) {
hashval = ((long)hashes[j][0]*item+hashes[j][1])%LONG_PRIME%w;
hashval = (hashes[j][0]*item+hashes[j][1])%LONG_PRIME%w;
minval = MIN(minval, C[j][hashval]);
}
return minval;
Expand All @@ -108,9 +108,9 @@ unsigned int CountMinSketch::estimate(const char *str) {
}

// generates aj,bj from field Z_p for use in hashing
void CountMinSketch::genajbj(int** hashes, int i) {
hashes[i][0] = int(float(rand())*float(LONG_PRIME)/float(RAND_MAX) + 1);
hashes[i][1] = int(float(rand())*float(LONG_PRIME)/float(RAND_MAX) + 1);
void CountMinSketch::genajbj(unsigned long** hashes, int i) {
hashes[i][0] = (unsigned long)(float(rand())*float(LONG_PRIME-2)/float(RAND_MAX) + 1);
hashes[i][1] = (unsigned long)(float(rand())*float(LONG_PRIME-2)/float(RAND_MAX) + 1);
}

// generates a hash value for a sting
Expand Down
6 changes: 3 additions & 3 deletions count_min_sketch.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -5,7 +5,7 @@
**/

// define some constants
# define LONG_PRIME 4294967311l
# define LONG_PRIME 4294967311ul
# define MIN(a,b) (a < b ? a : b)

/** CountMinSketch class definition here **/
Expand Down Expand Up @@ -34,10 +34,10 @@ class CountMinSketch {

// array of hash values for a particular item
// contains two element arrays {aj,bj}
int **hashes;
unsigned long **hashes;

// generate "new" aj,bj
void genajbj(int **hashes, int i);
void genajbj(unsigned long **hashes, int i);

public:
// constructor
Expand Down