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[hist] Fix GetRandom with negative bins #22980

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[hist] Fix GetRandom with negative bins #22980

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11 changes: 8 additions & 3 deletions hist/hist/src/TH1.cxx
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Original file line number Diff line number Diff line change
Expand Up @@ -2609,8 +2609,12 @@ Double_t TH1::ComputeIntegral(Bool_t onlyPositive, Option_t *option)

if (onlyPositive && y < 0) {
Error("ComputeIntegral","Bin content is negative - return a NaN value");
fIntegral[nbins] = TMath::QuietNaN();
break;
// Do not cache a partial integral: later rows could overwrite the
// failure marker, and other consumers assume fIntegral is a valid CDF.
// A subsequent request recomputes the integral and reports the error again.
delete[] fIntegral;
fIntegral = nullptr;
return TMath::QuietNaN();
}
fIntegral[ibin] = fIntegral[ibin - 1] + y;
}
Expand Down Expand Up @@ -5204,7 +5208,8 @@ Double_t TH1::GetRandom(TRandom *rng, Option_t *option) const
}
if (integral == 0) return 0;
// return a NaN in case some bins have negative content
if (integral == TMath::QuietNaN() ) return TMath::QuietNaN();
if (std::isnan(integral))
return TMath::QuietNaN();

Double_t r1 = (rng) ? rng->Rndm() : gRandom->Rndm();
Int_t ibin = TMath::BinarySearch(nbinsx,fIntegral,r1);
Expand Down
16 changes: 14 additions & 2 deletions hist/hist/src/TH2.cxx
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Expand Up @@ -28,6 +28,7 @@
#include "TVirtualHistPainter.h"
#include "snprintf.h"

#include <cmath>

/** \addtogroup Histograms
@{
Expand Down Expand Up @@ -765,7 +766,14 @@ void TH2::FillRandom(TH1 *h, Int_t ntimes, TRandom * rng)
Error("FillRandom", "Histograms with different dimensions"); return;
}

if (h->ComputeIntegral() == 0) return;
// Do not let GetRandom2 reuse an integral computed without the negative-bin check.
const Double_t integral = h->ComputeIntegral(true);
if (std::isnan(integral)) {
Error("FillRandom", "Histograms contains negative bins, does not represent probabilities");
return;
}
if (integral == 0)
return;

Int_t loop;
Double_t x,y;
Expand Down Expand Up @@ -1184,7 +1192,11 @@ void TH2::GetRandom2(Double_t &x, Double_t &y, TRandom *rng, Option_t *option)
}
if (integral == 0 ) { x = 0; y = 0; return;}
// case histogram has negative bins
if (integral == TMath::QuietNaN() ) { x = TMath::QuietNaN(); y = TMath::QuietNaN(); return;}
if (std::isnan(integral)) {
x = TMath::QuietNaN();
y = TMath::QuietNaN();
return;
}

if (!rng) rng = gRandom;
Double_t r1 = rng->Rndm();
Expand Down
17 changes: 15 additions & 2 deletions hist/hist/src/TH3.cxx
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Expand Up @@ -27,6 +27,7 @@

#include <algorithm>
#include <atomic>
#include <cmath>
#include <stdexcept>


Expand Down Expand Up @@ -959,7 +960,14 @@ void TH3::FillRandom(TH1 *h, Int_t ntimes, TRandom * rng)
Error("FillRandom", "Histograms with different dimensions"); return;
}

if (h->ComputeIntegral() == 0) return;
// Do not let GetRandom3 reuse an integral computed without the negative-bin check.
const Double_t integral = h->ComputeIntegral(true);
if (std::isnan(integral)) {
Error("FillRandom", "Histograms contains negative bins, does not represent probabilities");
return;
}
if (integral == 0)
return;

TH3 *h3 = (TH3*)h;
Int_t loop;
Expand Down Expand Up @@ -1302,7 +1310,12 @@ void TH3::GetRandom3(Double_t &x, Double_t &y, Double_t &z, TRandom *rng, Option
}
if (integral == 0 ) { x = 0; y = 0; z = 0; return;}
// case histogram has negative bins
if (integral == TMath::QuietNaN() ) { x = TMath::QuietNaN(); y = TMath::QuietNaN(); z = TMath::QuietNaN(); return;}
if (std::isnan(integral)) {
x = TMath::QuietNaN();
y = TMath::QuietNaN();
z = TMath::QuietNaN();
return;
}

if (!rng) rng = gRandom;
Double_t r1 = rng->Rndm();
Expand Down
145 changes: 145 additions & 0 deletions hist/hist/test/test_TH1.cxx
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Expand Up @@ -4,9 +4,11 @@
#include "TH2.h"
#include "TH3.h"
#include "TH1F.h"
#include "TH2Poly.h"
#include "THLimitsFinder.h"
#include "TDirectory.h"
#include "TList.h"
#include "TRandom3.h"
#include "TROOT.h"

#include <cmath>
Expand Down Expand Up @@ -562,3 +564,146 @@ TEST(TH1, GetCumulativeErrors)
}
}
}

namespace {

class TH1DIntegralAccess : public TH1D {
public:
using TH1D::TH1D;
bool HasCachedIntegral() const { return fIntegral != nullptr; }
};

} // namespace

TEST(TH1, GetRandomNegativeBin)
{
ROOT::TestSupport::CheckDiagsRAII diags;
diags.requiredDiag(kError, "TH1D::ComputeIntegral", "Bin content is negative - return a NaN value");

TH1DIntegralAccess h("hNegRandom", "", 2, 0., 2.);
h.SetBinContent(1, 1.);
h.SetBinContent(2, -0.25);

TRandom3 rng(1);
TRandom3 referenceRng(1);
EXPECT_TRUE(std::isnan(h.GetRandom(&rng)));
EXPECT_FALSE(h.HasCachedIntegral());
EXPECT_DOUBLE_EQ(rng.Rndm(), referenceRng.Rndm());
}

TEST(TH2, GetRandom2NegativeBin)
{
ROOT::TestSupport::CheckDiagsRAII diags;
diags.requiredDiag(kError, "TH2D::ComputeIntegral", "Bin content is negative - return a NaN value");

TH2D h("hNegRandom2", "", 2, 0., 2., 2, 0., 2.);
h.SetBinContent(1, 1, 1.);
h.SetBinContent(2, 1, -0.25);
h.SetBinContent(1, 2, 1.);
h.SetBinContent(2, 2, 1.);

TRandom3 rng(1);
TRandom3 referenceRng(1);
double x = 0., y = 0.;
h.GetRandom2(x, y, &rng);
EXPECT_TRUE(std::isnan(x));
EXPECT_TRUE(std::isnan(y));
EXPECT_DOUBLE_EQ(rng.Rndm(), referenceRng.Rndm());
}

TEST(TH3, GetRandom3NegativeBin)
{
ROOT::TestSupport::CheckDiagsRAII diags;
diags.requiredDiag(kError, "TH3D::ComputeIntegral", "Bin content is negative - return a NaN value");

TH3D h("hNegRandom3", "", 2, 0., 2., 2, 0., 2., 2, 0., 2.);
h.SetBinContent(1, 1, 1, 1.);
h.SetBinContent(2, 2, 2, -0.25);

TRandom3 rng(1);
TRandom3 referenceRng(1);
double x = 0., y = 0., z = 0.;
h.GetRandom3(x, y, z, &rng);
EXPECT_TRUE(std::isnan(x));
EXPECT_TRUE(std::isnan(y));
EXPECT_TRUE(std::isnan(z));
EXPECT_DOUBLE_EQ(rng.Rndm(), referenceRng.Rndm());
}

TEST(TH2, FillRandomNegativeBin)
{
ROOT::TestSupport::CheckDiagsRAII diags;
diags.requiredDiag(kError, "TH2D::ComputeIntegral", "Bin content is negative - return a NaN value");
diags.requiredDiag(kError, "TH2D::FillRandom",
"Histograms contains negative bins, does not represent probabilities");

TH2D src("hFillRandom2Src", "", 2, 0., 2., 2, 0., 2.);
src.SetBinContent(1, 1, 1.);
src.SetBinContent(2, 1, -0.25);
src.SetBinContent(1, 2, 1.);
src.SetBinContent(2, 2, 1.);

TH2D dest("hFillRandom2Dest", "", 2, 0., 2., 2, 0., 2.);
TRandom3 rng(1);
dest.FillRandom(&src, 1, &rng);
EXPECT_EQ(dest.GetEntries(), 0.);
}

TEST(TH3, FillRandomNegativeBin)
{
ROOT::TestSupport::CheckDiagsRAII diags;
diags.requiredDiag(kError, "TH3D::ComputeIntegral", "Bin content is negative - return a NaN value");
diags.requiredDiag(kError, "TH3D::FillRandom",
"Histograms contains negative bins, does not represent probabilities");

TH3D src("hFillRandom3Src", "", 2, 0., 2., 2, 0., 2., 2, 0., 2.);
src.SetBinContent(1, 1, 1, 1.);
src.SetBinContent(2, 2, 2, -0.25);

TH3D dest("hFillRandom3Dest", "", 2, 0., 2., 2, 0., 2., 2, 0., 2.);
TRandom3 rng(1);
dest.FillRandom(&src, 1, &rng);
EXPECT_EQ(dest.GetEntries(), 0.);
}

TEST(TH2, FillRandomPositiveBins)
{
ROOT::TestSupport::CheckDiagsRAII diags;
TRandom3 rng(1);

TH2D src("hFillRandom2PositiveSrc", "", 1, 0., 1., 1, 0., 1.);
src.SetBinContent(1, 1, 1.);
TH2D dest("hFillRandom2PositiveDest", "", 1, 0., 1., 1, 0., 1.);
dest.FillRandom(&src, 1, &rng);
EXPECT_EQ(dest.GetEntries(), 1.);
EXPECT_EQ(dest.Integral(), 1.);
}

TEST(TH3, FillRandomPositiveBins)
{
ROOT::TestSupport::CheckDiagsRAII diags;
TRandom3 rng(1);

TH3D src("hFillRandom3PositiveSrc", "", 1, 0., 1., 1, 0., 1., 1, 0., 1.);
src.SetBinContent(1, 1, 1, 1.);
TH3D dest("hFillRandom3PositiveDest", "", 1, 0., 1., 1, 0., 1., 1, 0., 1.);
dest.FillRandom(&src, 1, &rng);
EXPECT_EQ(dest.GetEntries(), 1.);
EXPECT_EQ(dest.Integral(), 1.);
}

TEST(TH2Poly, GetRandom2NotImplemented)
{
ROOT::TestSupport::CheckDiagsRAII diags;
diags.requiredDiag(kError, "TH2Poly::ComputeIntegral", "Not implemented for TH2Poly");

TH2Poly h("hPolyRandom", "", 0., 2., 0., 2.);
h.AddBin(0., 0., 1., 1.);
h.AddBin(1., 1., 2., 2.);

TRandom3 rng(1);
double x = 0., y = 0.;
h.GetRandom2(x, y, &rng);
EXPECT_TRUE(std::isnan(x));
EXPECT_TRUE(std::isnan(y));
}