std::vector optimisation required
- by marcp
I've written a routine that uses std::vector<double> rather heavily. It runs rather slowly and AQTime seems to imply that I am constructing mountains of vectors but I'm not sure why I would be. For some context, my sample run iterates 10 times. Each iteration copies 3 c arrays of ~400 points into vectors and creates 3 new same sized vectors for output. Each output point might be the result of summing up to 20 points from 2 of the input vectors, which works out to a worst case of 10*400*3*2*20 = 480,000 dereferences. Incredibly the profiler indicates that some of the std:: methods are being called 46 MILLION times. I suspect I'm doing something wrong!
Some code:
vector<double>gdbChannel::GetVector() {
if (fHaveDoubleData & (fLength > 0)) {
double * pD = getDoublePointer();
vector<double>v(pD, pD + fLength);
return v;
} else {
throw(Exception("attempt to retrieve vector on empty line")); ;
}
}
void gdbChannel::SaveVector(GX_HANDLE _hLine, const vector<double> & V) {
if (hLine != _hLine) {
GetLine(_hLine, V.size(), true);
}
GX_DOUBLE * pData = getDoublePointer();
memcpy(pData, &V[0], V.size()*sizeof(V[0]));
ReplaceData();
}
///This routine gets called 10 times
bool SpecRatio::DoWork(GX_HANDLE_PTR pLine) {
if (!(hKin.GetLine(*pLine, true) && hUin.GetLine(*pLine, true) && hTHin.GetLine(*pLine, true))) {
return true;
}
vector<double>vK = hKin.GetVector();
vector<double>vU = hUin.GetVector();
vector<double>vTh = hTHin.GetVector();
if ((vK.size() == 0) || (vU.size() == 0) || (vTh.size() == 0)) {
return true;
}
///TODO: confirm all vectors the same lenghth
len = vK.size();
vUK.clear(); // these 3 vectors are declared as private class members
vUTh.clear();
vThK.clear();
vUK.reserve(len);
vUTh.reserve(len);
vThK.reserve(len);
// TODO: ensure everything is same fidincr, fidstart and length
for (int i = 0; i < len; i++) {
if (vK.at(i) < MinK) {
vUK.push_back(rDUMMY);
vUTh.push_back(rDUMMY);
vThK.push_back(rDUMMY);
} else {
vUK.push_back(RatioPoint(vU, vK, i, UMin, KMin));
vUTh.push_back(RatioPoint(vU, vTh, i, UMin, ThMin));
vThK.push_back(RatioPoint(vTh, vK, i, ThMin, KMin));
}
}
hUKout.setFidParams(hKin);
hUKout.SaveVector(*pLine, vUK);
hUTHout.setFidParams(hKin);
hUTHout.SaveVector(*pLine, vUTh);
hTHKout.setFidParams(hKin);
hTHKout.SaveVector(*pLine, vThK);
return TestError();
}
double SpecRatio::VValue(vector<double>V, int Index) {
double result;
if ((Index < 0) || (Index >= len)) {
result = 0;
} else {
try {
result = V.at(Index);
if (OasisUtils::isDummy(result)) {
result = 0;
}
}
catch (out_of_range) {
result = 0;
}
}
return result;
}
double SpecRatio::RatioPoint(vector<double>Num, vector<double>Denom, int Index, double NumMin, double DenomMin) {
double num = VValue(Num, Index);
double denom = VValue(Denom, Index);
int s = 0;
// Search equalled 10 in this case
while (((num < NumMin) || (denom < DenomMin)) && (s < Search)) {
num += VValue(Num, Index - s) + VValue(Num, Index + s);
denom += VValue(Denom, Index - s) + VValue(Denom, Index + s);
s++;
}
if ((num < NumMin) || (denom < DenomMin)) {
return rDUMMY;
} else {
return num / denom;
}
}
The top AQTime offenders are:
std::_Uninit_copy , double *, std::allocator 3.65 secs
and 115731 Hits
std::_Construct 1.69 secs and 46450637 Hits
std::_Vector_const_iterator ::operator
!=1.66 secs and 46566395 Hits and so on...
std::allocator<double>::construct,
operator new,
std::_Vector_const_iterator<double, std::allocator<double> >::operator ++, std::_Vector_const_iterator<double, std::allocator<double> >::operator *
std::_Vector_const_iterator<double, std::allocator<double> >::operator ==
each get called over 46 million times.
I'm obviously doing something wrong to cause all these objects to be created. Can anyone see my error(s)?
