/*!
* \brief l_dnaIntersectionByHash()
*
* \param[in] da1, da2
* \return dad intersection of the number arrays, or NULL on error
*
* <pre>
* Notes:
* (1) This uses the same method for building the intersection set
* as ptaIntersectionByHash() and sarrayIntersectionByHash().
* </pre>
*/
L_DNA *
l_dnaIntersectionByHash(L_DNA *da1,
L_DNA *da2)
{
l_int32 n1, n2, nsmall, nbuckets, i, index1, index2;
l_uint32 nsize2;
l_uint64 key;
l_float64 val;
L_DNAHASH *dahash1, *dahash2;
L_DNA *da_small, *da_big, *dad;
PROCNAME("l_dnaIntersectionByHash");
if (!da1)
return (L_DNA *)ERROR_PTR("da1 not defined", procName, NULL);
if (!da2)
return (L_DNA *)ERROR_PTR("da2 not defined", procName, NULL);
/* Put the elements of the biggest array into a dnahash */
n1 = l_dnaGetCount(da1);
n2 = l_dnaGetCount(da2);
da_small = (n1 < n2) ? da1 : da2; /* do not destroy da_small */
da_big = (n1 < n2) ? da2 : da1; /* do not destroy da_big */
dahash1 = l_dnaHashCreateFromDna(da_big);
/* Build up the intersection of numbers. Add to %dad
* if the number is in da_big (using dahash1) but hasn't
* yet been seen in the traversal of da_small (using dahash2). */
dad = l_dnaCreate(0);
nsmall = l_dnaGetCount(da_small);
findNextLargerPrime(nsmall / 20, &nsize2); /* buckets in hash table */
dahash2 = l_dnaHashCreate(nsize2, 0);
nbuckets = l_dnaHashGetCount(dahash2);
for (i = 0; i < nsmall; i++) {
l_dnaGetDValue(da_small, i, &val);
l_dnaFindValByHash(da_big, dahash1, val, &index1);
if (index1 >= 0) { /* found */
l_dnaFindValByHash(da_small, dahash2, val, &index2);
if (index2 == -1) { /* not found */
l_dnaAddNumber(dad, val);
l_hashFloat64ToUint64(nbuckets, val, &key);
l_dnaHashAdd(dahash2, key, (l_float64)i);
}
}
}
l_dnaHashDestroy(&dahash1);
l_dnaHashDestroy(&dahash2);
return dad;
}
/*!
* \brief l_dnaFindValByHash()
*
* \param[in] da
* \param[in] dahash containing indices into %da
* \param[in] val searching for this number in %da
* \param[out] pindex index into da if found; -1 otherwise
* \return 0 if OK; 1 on error
*
* <pre>
* Notes:
* (1) Algo: hash %val into a key; hash the key to get the dna
* in %dahash (that holds indices into %da); traverse
* the dna of indices looking for %val in %da.
* </pre>
*/
l_ok
l_dnaFindValByHash(L_DNA *da,
L_DNAHASH *dahash,
l_float64 val,
l_int32 *pindex)
{
l_int32 i, nbuckets, nvals, indexval;
l_float64 vali;
l_uint64 key;
L_DNA *da1;
PROCNAME("l_dnaFindValByHash");
if (!pindex)
return ERROR_INT("&index not defined", procName, 1);
*pindex = -1;
if (!da)
return ERROR_INT("da not defined", procName, 1);
if (!dahash)
return ERROR_INT("dahash not defined", procName, 1);
nbuckets = l_dnaHashGetCount(dahash);
l_hashFloat64ToUint64(nbuckets, val, &key);
da1 = l_dnaHashGetDna(dahash, key, L_NOCOPY);
if (!da1) return 0;
/* Run through da1, looking for this %val */
nvals = l_dnaGetCount(da1);
for (i = 0; i < nvals; i++) {
l_dnaGetIValue(da1, i, &indexval);
l_dnaGetDValue(da, indexval, &vali);
if (val == vali) {
*pindex = indexval;
return 0;
}
}
return 0;
}
/*!
* ptaFindPtByHash()
*
* Input: pta
* dahash (built from pta)
* x, y (arbitrary points)
* &index (<return> index into pta if (x,y) is in pta;
* -1 otherwise)
* Return: 0 if OK, 1 on error
*
* Notes:
* (1) Fast lookup in dnaHash associated with a pta, to see if a
* random point (x,y) is already stored in the hash table.
*/
l_int32
ptaFindPtByHash(PTA *pta,
L_DNAHASH *dahash,
l_int32 x,
l_int32 y,
l_int32 *pindex)
{
l_int32 i, nbuckets, nvals, index, xi, yi;
l_uint64 key;
L_DNA *da;
PROCNAME("ptaFindPtByHash");
if (!pindex)
return ERROR_INT("&index not defined", procName, 1);
*pindex = -1;
if (!pta)
return ERROR_INT("pta not defined", procName, 1);
if (!dahash)
return ERROR_INT("dahash not defined", procName, 1);
nbuckets = l_dnaHashGetCount(dahash);
l_hashPtToUint64Fast(nbuckets, x, y, &key);
da = l_dnaHashGetDna(dahash, key, L_NOCOPY);
if (!da) return 0;
/* Run through the da, looking for this point */
nvals = l_dnaGetCount(da);
for (i = 0; i < nvals; i++) {
l_dnaGetIValue(da, i, &index);
ptaGetIPt(pta, index, &xi, &yi);
if (x == xi && y == yi) {
*pindex = index;
return 0;
}
}
return 0;
}
