/*Get qgram distances
* Input
* s: a string
* t: a string
* x: length of s
* y: length of t
* q: the 'q' in q-gram
* Q: a qtree
* int: distance distance function to compute:
* 0 : q-gram distance
* 1 : cosine distance
* 2 : jaccard distance
*
*
* Return values:
* >=0 : qgram distance
* -1 : infinite distance
* -2 : Not enough memory
*/
double qgram_dist(
unsigned int *s,
int x,
unsigned int *t,
int y,
unsigned int q,
qtree **Qp,
int distance
){
// rare edge case: q==0. Note that we return 0 for all cases where
// q equals zero. In the R journal paper we used Inf for cases where
// q=0 and |s| or |t| > 0
if ( q == 0 ) return 0.0;
double dist[3] = {0,0,0};
*Qp = push_string(s, x, q, *Qp, 0, 2);
*Qp = push_string(t, y, q, *Qp, 1, 2);
if (*Qp == NULL) return 0;
qtree *Q = *Qp;
switch ( distance ){
case 0:
getdist(Q,dist);
break;
case 1:
getcosine(Q, dist);
if (dist[0]==dist[1] && dist[0]==dist[2]){
// strings are equal. Prevent machine rounding about 0.0
dist[0] = 0.0;
} else {
// there are several ways to express the rhs (including ones that give 0L
// at equal strings) but this has least chance of overflow
// fabs is taken to avoid numerical -0.
dist[0] = fabs(1.0 - dist[0]/(sqrt(dist[1]) * sqrt(dist[2])));
}
break;
case 2:
getjaccard(*Qp,dist);
dist[0] = 1.0 - dist[0]/dist[1];
break;
default:
break;
}
return dist[0];
}
/*Get qgram distances
* Input
* s: a string
* t: a string
* x: length of s
* y: length of t
* q: the 'q' in q-gram
* Q: a qtree
* int: distance distance function to compute:
* 0 : q-gram distance
* 1 : cosine distance
* 2 : jaccard distance
*
*
* Return values:
* >=0 : qgram distance
* -1 : infinite distance
* -2 : Not enough memory
*/
double qgram_dist(
unsigned int *s,
int x,
unsigned int *t,
int y,
unsigned int q,
qtree *Q,
int distance
){
// return -1 when q is larger than the length of the shortest string.
if ( q > (x <= y ? x : y) ) return -1.0;
// rare edge case: q==0. Note that we return 0 for all cases where
// q equals zero. In the R journal paper we used Inf for cases where
// q=0 and |s| or |t| > 0
if ( q == 0 ) return 0.0;
double dist[3] = {0,0,0};
Q = push_string(s, x, q, Q, 0, 2);
if (Q == NULL) return -2.0;
Q = push_string(t, y, q, Q, 1, 2);
if (Q == NULL) return -2.0;
switch ( distance ){
case 0:
getdist(Q,dist);
break;
case 1:
getcosine(Q, dist);
if (dist[0]==dist[1] && dist[0]==dist[2]){
// strings are equal. Prevent machine rounding about 0.0
dist[0] = 0.0;
} else {
// there are several ways to express the rhs (including ones that give 0L
// at equal strings) but this has least chance of overflow.
dist[0] = 1.0 - dist[0]/(sqrt(dist[1]) * sqrt(dist[2]));
}
break;
case 2:
getjaccard(Q,dist);
dist[0] = 1.0 - dist[0]/dist[1];
break;
default:
break;
}
return dist[0];
}
