// A CostFunc that takes the variance of step into account in the cost.
inT64 DPPoint::CostWithVariance(const DPPoint *prev) {
if (prev == NULL || prev == this) {
UpdateIfBetter(0, 1, NULL, 0, 0, 0);
return 0;
}
int delta = this - prev;
inT32 n = prev->n_ + 1;
inT32 sig_x = prev->sig_x_ + delta;
inT64 sig_xsq = prev->sig_xsq_ + delta * delta;
inT64 cost = (sig_xsq - sig_x * sig_x / n) / n;
cost += prev->total_cost_;
UpdateIfBetter(cost, prev->total_steps_ + 1, prev, n, sig_x, sig_xsq);
return cost;
}
// A CostFunc that takes the variance of step into account in the cost.
int64_t DPPoint::CostWithVariance(const DPPoint* prev) {
if (prev == nullptr || prev == this) {
UpdateIfBetter(0, 1, nullptr, 0, 0, 0);
return 0;
}
int delta = this - prev;
int32_t n = prev->n_ + 1;
int32_t sig_x = prev->sig_x_ + delta;
int64_t sig_xsq = prev->sig_xsq_ + delta * delta;
int64_t cost = (sig_xsq - sig_x * sig_x / n) / n;
cost += prev->total_cost_;
UpdateIfBetter(cost, prev->total_steps_ + 1, prev, n, sig_x, sig_xsq);
return cost;
}
