using namespace RooFit;

RooMsgService::instance().getStream(1).removeTopic(Minimization);
RooMsgService::instance().getStream(1).removeTopic(Fitting);

RooRealVar x("x", "x", -10, 10);

RooRealVar mu("mu", "mu", 0.0, -10, 10);
RooRealVar sigma("sigma", "sigma", 1.0, 0.1, 2.0);

RooGaussian gauss("gauss", "gauss", x, mu, sigma);

RooRealVar mu_obs("mu_obs", "mu_obs", 1.0, -10, 10);
mu_obs.setConstant();

RooGaussian constraint("constraint", "constraint", mu_obs, mu, 0.1);

RooProdPdf model("model", "model", {gauss, constraint});

std::unique_ptr<RooDataSet> dataGlob{model.generate({mu_obs}, 1)};

double mu_obs_orig_val = mu_obs.getVal();

RooArgSet{mu_obs}.assign(*dataGlob->get(0));

std::unique_ptr<RooDataSet> data{model.generate({x}, 50)};

data->setGlobalObservables({mu_obs});

mu_obs.setVal(mu_obs_orig_val);

RooArgSet modelParameters;
model.getParameters(data->get(), modelParameters);
RooArgSet origParameters;
modelParameters.snapshot(origParameters);

using FitRes = std::unique_ptr<RooFitResult>;

std::cout << "1. model.fitTo(*data, GlobalObservables(mu_obs))\n";
std::cout << "------------------------------------------------\n";
FitRes res1{model.fitTo(*data, GlobalObservables(mu_obs), PrintLevel(-1), Save())};
res1->Print();
modelParameters.assign(origParameters);

std::cout << "2. model.fitTo(*data)\n";
std::cout << "---------------------\n";
FitRes res2{model.fitTo(*data, PrintLevel(-1), Save())};
res2->Print();
modelParameters.assign(origParameters);

std::cout << "3. model.fitTo(*data, GlobalObservables(mu_obs), GlobalObservablesSource(\"model\"))\n";
std::cout << "------------------------------------------------\n";
FitRes res3{model.fitTo(*data, GlobalObservables(mu_obs), GlobalObservablesSource("model"), PrintLevel(-1), Save())};
res3->Print();
modelParameters.assign(origParameters);

%jsroot on
gROOT->GetListOfCanvases()->Draw()