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Tony Hoyle <tmh at nodomain.org> wrote:
TH> It really doesn't make a lot of difference - the time taken to setup the
TH> map and copy the extra strings around offsets the advantages. The
TH> common case is maybe half a dozen locks active at a time, where the
TH> linear scan isn't significantly better than the lookup of a map (in the
TH> general case 90% of the loop is incrementing a pointer and comparing two
TH> integers. If you introduce a map it will always do string compares
TH> which is slower).
To optimize number of compare operations we can redefined comparision
operator.
/* contains upper case value for each character */
unsigned char UpperCaseTable[256];
class LockPtrLessOperator {
public:
bool operator()(const Lock*& left, const Lock*& right) const {
if (left->length != right->length) {
return left->length < right->length;
}
const char *path1 = left->path.c_str();
const char *path2 = right->path.c_str();
for (int i = 0; i < left->length; ++i) {
if (UpperCaseTable[(int)path1[i]] < UpperCaseTable[(int)path2[i]]) {
return true;
}
}
return false;
}
};
map<Lock*, map<site_t,Lock*>, LockPtrLessOperator>
Without string copying. Compare operations have almost the same cost
as in the current implementation. This solution is more scalable for
large number of concurrent users.
--
Best regards,
alexey-panchenko mailto:alexey-panchenko at hotmail.ru