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[hist] Fix computation of number of entries in ResetStats #21254

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Merged
lmoneta merged 1 commit into from
Feb 24, 2026
Merged

[hist] Fix computation of number of entries in ResetStats #21254

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2 changes: 0 additions & 2 deletions bindings/pyroot/pythonizations/test/uhi_indexing.py
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Expand Up @@ -296,7 +296,6 @@ def test_statistics_slice(self, hist_setup):
sliced_hist_full = hist_setup[...]

assert hist_setup.GetEffectiveEntries() == pytest.approx(sliced_hist_full.GetEffectiveEntries())
assert sliced_hist_full.GetEntries() == pytest.approx(sliced_hist_full.GetEffectiveEntries())
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assert hist_setup.Integral() == pytest.approx(sliced_hist_full.Integral())

# Check if slicing over a range updates the statistics
Expand All @@ -307,7 +306,6 @@ def test_statistics_slice(self, hist_setup):

assert hist_setup.Integral() == sliced_hist.Integral()
assert hist_setup.GetEffectiveEntries() == pytest.approx(sliced_hist.GetEffectiveEntries())
assert sliced_hist.GetEntries() == pytest.approx(sliced_hist.GetEffectiveEntries())
assert hist_setup.GetStdDev() == pytest.approx(sliced_hist.GetStdDev(), rel=10e-5)
assert hist_setup.GetMean() == pytest.approx(sliced_hist.GetMean(), rel=10e-5)

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2 changes: 1 addition & 1 deletion hist/hist/inc/TH1.h
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Expand Up @@ -553,7 +553,7 @@ class TH1 : public TNamed, public TAttLine, public TAttFill, public TAttMarker {
virtual void GetStats(Double_t *stats) const;
virtual Double_t GetStdDev(Int_t axis=1) const;
virtual Double_t GetStdDevError(Int_t axis=1) const;
Double_t GetSumOfAllWeights(const bool includeOverflow) const;
Double_t GetSumOfAllWeights(const bool includeOverflow, Double_t * sumWeightSquare = nullptr) const;
/// Return the sum of weights across all bins excluding under/overflows.
/// \see TH1::GetSumOfAllWeights()
virtual Double_t GetSumOfWeights() const { return GetSumOfAllWeights(false); }
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65 changes: 50 additions & 15 deletions hist/hist/src/TH1.cxx
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Expand Up @@ -967,11 +967,13 @@ Bool_t TH1::Add(const TH1 *h1, Double_t c1)
return (iret >= 0);
}

// Create Sumw2 if h1 has Sumw2 set
// Create Sumw2 if h1 has Sumw2 set
if (fSumw2.fN == 0 && h1->GetSumw2N() != 0) Sumw2();
// In addition, create Sumw2 if is not a simple addition, otherwise errors will not be correctly computed
if (fSumw2.fN == 0 && c1 != 1.0) Sumw2();

// - Add statistics
Double_t entries = TMath::Abs( GetEntries() + c1 * h1->GetEntries() );
// - Add statistics (for c1=1)
Double_t entries = GetEntries() + h1->GetEntries();

// statistics can be preserved only in case of positive coefficients
// otherwise with negative c1 (histogram subtraction) one risks to get negative variances
Expand Down Expand Up @@ -1048,7 +1050,15 @@ Bool_t TH1::Add(const TH1 *h1, Double_t c1)
else s1[i] += c1*s2[i];
}
PutStats(s1);
SetEntries(entries);
if (c1 == 1.0)
SetEntries(entries);
else {
// compute entries as effective entries in case of
// weights different than 1
double sumw2 = 0;
double sumw = GetSumOfAllWeights(true, &sumw2);
if (sumw2 > 0) SetEntries( sumw*sumw/sumw2);
}
}
return kTRUE;
}
Expand Down Expand Up @@ -1133,7 +1143,8 @@ Bool_t TH1::Add(const TH1 *h1, const TH1 *h2, Double_t c1, Double_t c2)

// Create Sumw2 if h1 or h2 have Sumw2 set
if (fSumw2.fN == 0 && (h1->GetSumw2N() != 0 || h2->GetSumw2N() != 0)) Sumw2();

// Create also Sumw2 if not a simple addition (c1 = 1, c2 = 1)
if (fSumw2.fN == 0 && (c1 != 1.0 || c2 != 1.0)) Sumw2();
// - Add statistics
Double_t nEntries = TMath::Abs( c1*h1->GetEntries() + c2*h2->GetEntries() );

Expand Down Expand Up @@ -1240,9 +1251,18 @@ Bool_t TH1::Add(const TH1 *h1, const TH1 *h2, Double_t c1, Double_t c2)
ResetStats();
}
else {
// update statistics (do here to avoid changes by SetBinContent) FIXME remove???
// update statistics
PutStats(s3);
SetEntries(nEntries);
// previous entries are correct only if c1=1 and c2=1
if (c1 == 1.0 && c2 == 1.0)
SetEntries(nEntries);
else {
// compute entries as effective entries in case of
// weights different than 1
double sumw2 = 0;
double sumw = GetSumOfAllWeights(true, &sumw2);
if (sumw2 > 0) SetEntries( sumw*sumw/sumw2);
}
}

return kTRUE;
Expand Down Expand Up @@ -7959,33 +7979,48 @@ void TH1::ResetStats()
fEntries = 1; // to force re-calculation of the statistics in TH1::GetStats
GetStats(stats);
PutStats(stats);
fEntries = TMath::Abs(fTsumw);
// use effective entries for weighted histograms: (sum_w) ^2 / sum_w2
if (fSumw2.fN > 0 && fTsumw > 0 && stats[1] > 0 ) fEntries = stats[0]*stats[0]/ stats[1];
// histogram entries should include always underflows and overflows
if (GetStatOverflowsBehaviour() && !fXaxis.TestBit(TAxis::kAxisRange))
fEntries = TMath::Abs(fTsumw);
else {
Double_t sumw2 = 0;
Double_t * p_sumw2 = (fSumw2.fN > 0) ? &sumw2 : nullptr;
fEntries = GetSumOfAllWeights(true, p_sumw2);
// use effective entries for weighted histograms: (sum_w) ^2 / sum_w2
if (p_sumw2 && sumw2 > 0) fEntries = fEntries*fEntries/ sumw2;
}
}

////////////////////////////////////////////////////////////////////////////////
/// Return the sum of all weights
/// Return the sum of all weights and optionally also the sum of weight squares
/// \param includeOverflow true to include under/overflows bins, false to exclude those.
/// \note Different from TH1::GetSumOfWeights, that always excludes those

Double_t TH1::GetSumOfAllWeights(const bool includeOverflow) const
Double_t TH1::GetSumOfAllWeights(const bool includeOverflow, Double_t * sumWeightSquare) const
{
if (fBuffer) const_cast<TH1*>(this)->BufferEmpty();

const Int_t start = (includeOverflow ? 0 : 1);
const Int_t lastX = fXaxis.GetNbins() + (includeOverflow ? 1 : 0);
const Int_t lastY = fYaxis.GetNbins() + (includeOverflow ? 1 : 0);
const Int_t lastZ = fZaxis.GetNbins() + (includeOverflow ? 1 : 0);
const Int_t lastY = (fDimension > 1) ? (fYaxis.GetNbins() + (includeOverflow ? 1 : 0)) : start;
const Int_t lastZ = (fDimension > 2) ? (fZaxis.GetNbins() + (includeOverflow ? 1 : 0)) : start;
Double_t sum =0;
Double_t sum2 = 0;
for(auto binz = start; binz <= lastZ; binz++) {
for(auto biny = start; biny <= lastY; biny++) {
for(auto binx = start; binx <= lastX; binx++) {
const auto bin = GetBin(binx, biny, binz);
sum += RetrieveBinContent(bin);
sum += RetrieveBinContent(bin);
if (sumWeightSquare && fSumw2.fN > 0) sum2 += GetBinErrorSqUnchecked(bin);
}
}
}
if (sumWeightSquare) {
if (fSumw2.fN > 0)
*sumWeightSquare = sum2;
else
*sumWeightSquare = sum;
}
return sum;
}

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2 changes: 2 additions & 0 deletions hist/hist/src/TProfileHelper.h
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Expand Up @@ -108,6 +108,8 @@ Bool_t TProfileHelper::Add(T* p, const TH1 *h1, const TH1 *h2, Double_t c1, Dou

// create sumw2 per bin if not set
if (p->fBinSumw2.fN == 0 && (p1->fBinSumw2.fN != 0 || p2->fBinSumw2.fN != 0)) p->Sumw2();
// create sumw2 also for the case where coefficients are not equal to 1
if (p->fSumw2.fN == 0 && (c1 != 1.0 || c2 != 1.0)) p->Sumw2();

// Make the loop over the bins to calculate the Addition
Double_t *cu1 = p1->GetW(); Double_t *cu2 = p2->GetW();
Expand Down
37 changes: 34 additions & 3 deletions test/stressHistogram.cxx
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Expand Up @@ -127,7 +127,7 @@ enum compareOptions {
int defaultEqualOptions = 0; //cmpOptPrint;
//int defaultEqualOptions = cmpOptDebug;

Bool_t cleanHistos = kTRUE; // delete histogram after testing (swicth off in case of debugging)
Bool_t cleanHistos = kTRUE; // delete histogram after testing (switch off in case of debugging)

const double defaultErrorLimit = 1.E-10;

Expand All @@ -142,7 +142,7 @@ const char* refFileName = "./stressHistogram.5.18.00.root";

TRandom2 r;
// set to zero if want to run different numbers every time
const int initialSeed = 0;
int initialSeed = 0;



Expand Down Expand Up @@ -181,7 +181,6 @@ bool testAdd1()
TH1D* h2 = new TH1D("t1D1_h2", "h2-Title", numberOfBins, minRange, maxRange);
TH1D* h3 = new TH1D("t1D1_h3", "h3=c1*h1+c2*h2", numberOfBins, minRange, maxRange);

h1->Sumw2();h2->Sumw2();h3->Sumw2();

FillHistograms(h1, h3, 1.0, c1);
FillHistograms(h2, h3, 1.0, c2);
Expand Down Expand Up @@ -11106,6 +11105,11 @@ int stressHistogram(int testNumber = 0)

// Test 7
// Add Tests
// for adding we do not need to set by default Sumw2
// we test that automatically is set
bool globalSumw2 = TH1::GetDefaultSumw2();
if (globalSumw2) TH1::SetDefaultSumw2(false);

const unsigned int numberOfAdds = 22;
pointer2Test addTestPointer[numberOfAdds] = { testAdd1, testAddProfile1,
testAdd2, testAddProfile2,
Expand All @@ -11126,6 +11130,8 @@ int stressHistogram(int testNumber = 0)
"Add tests for 1D, 2D and 3D Histograms and Profiles..............",
addTestPointer };

if (globalSumw2) TH1::SetDefaultSumw2(true);

// Test 8
// Multiply Tests
const unsigned int numberOfMultiply = 20;
Expand Down Expand Up @@ -11911,6 +11917,21 @@ int compareStatistics( TH1* h1, TH1* h2, bool debug, double ERRORLIMIT)
<< " | " << fabs( stats1[0] - stats2[0] )
<< " " << differents
<< std::endl;
// check the sum of weights (excluding underflows/overflows)
differents += (bool) equals( h1->GetSumOfWeights(), h2->GetSumOfWeights(), 100*ERRORLIMIT);
if ( debug )
std::cout << "Sum Of Weigths(2): " << h1->GetSumOfWeights() << " " << h2->GetSumOfWeights()
<< " | " << fabs( h2->GetSumOfWeights() - h1->GetSumOfWeights() )
<< " " << differents
<< std::endl;
// check the sum of all weights (including underflows/overflows)
differents += (bool) equals( h1->GetSumOfAllWeights(true), h2->GetSumOfAllWeights(true), 100*ERRORLIMIT);
if ( debug )
std::cout << "Sum Of All Weigths (with u/o): " << h1->GetSumOfAllWeights(true) << " " << h2->GetSumOfAllWeights(true)
<< " | " << fabs( h2->GetSumOfAllWeights(true) - h1->GetSumOfAllWeights(true) )
<< " " << differents
<< std::endl;


if (TMath::AreEqualRel(stats1[0], h1->GetEffectiveEntries() , 1.E-12) ) {
// unweighted histograms - check also number of entries
Expand All @@ -11920,6 +11941,16 @@ int compareStatistics( TH1* h1, TH1* h2, bool debug, double ERRORLIMIT)
<< " | " << fabs( h1->GetEntries() - h2->GetEntries() )
<< " " << differents
<< std::endl;

// check that the number of entries is equal to sum of all weights
// this is not valid for TProfiles
if (!h1->InheritsFrom(TProfile::Class()) && !h1->InheritsFrom(TProfile2D::Class()) && !h1->InheritsFrom(TProfile3D::Class())) {
differents += (bool) equals( h1->GetEntries(), h2->GetSumOfAllWeights(true), 100*ERRORLIMIT);
if (debug)
std::cout << "Entries vs Sum of All Weights: " << h1->GetEntries() << " " << h2->GetSumOfAllWeights(true)
<< " | " << fabs( h1->GetEntries() - h2->GetSumOfAllWeights(true) )
<< " " << differents << std::endl;
}
}

// Number of Effective Entries
Expand Down
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