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pagerank.c
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pagerank.c
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#include <stdlib.h>
#include <stdio.h>
#include <math.h>
#include "pagerank.h"
#include "table.h"
#ifndef MIN
#define MIN(A, B) ((A) < (B)) ? (A) : (B)
#endif
#ifndef MAX
#define MAX(A, B) ((A) > (B)) ? (A) : (B)
#endif
Array * page_rank(Table * inbound, unsigned int order, float alpha, float convergence, unsigned int max_times)
{
register int t = 0, k, i;
register float norm2 = 1.0, prod_scalar, x;
unsigned int total_size = order;
Array * vector = initial(total_size);
Array * new_vector = initial(total_size);
Array * tmp;
x = 1.0 - alpha;
while (t < max_times && norm2 >= convergence) {
t++;
norm2 = 0.0;
prod_scalar = 0.0;
for (k = 0; k < total_size; k++) {
if (is_sink(inbound, k))
prod_scalar += array_get(vector, k) * alpha;
}
prod_scalar += x;
for (k = 0; k < total_size; k++) {
array_set(new_vector, k, prod_scalar);
if (!is_sink(inbound, k)) {
tmp = table_get(inbound, k);
for (i = 0; i < array_len(tmp); i++) {
array_incr(new_vector, k,
array_get(vector,
(int)array_get(tmp, i)) *
alpha);
}
}
norm2 += (array_get(new_vector, k) - array_get(vector, k)) *
(array_get(new_vector, k) - array_get(vector, k));
}
t++;
norm2 = sqrt((double)norm2) / total_size;
array_copy(vector, new_vector);
}
array_delete(new_vector);
return normalize(vector);
}
Array * initial(unsigned int order)
{
register int i;
register float value = 1.0 / order;
Array * vector = array_init(value);
for (i = 1; i < order; i++)
array_push(vector, value);
return vector;
}
Array * normalize(Array * vector)
{
register int i;
register double sum = 0;
for (i = 0; i < array_len(vector); i++)
sum += array_get(vector, i);
for (i = 0; i < array_len(vector); i++)
array_diveq(vector, i, sum);
return vector;
}