class Generator : public o2::eventgen::GeneratorPythia8 {

public:

Generator() = default;

~Generator() = default;

/** static functions that define the information

stored in the header (key and data type)

and provide a mean to retrieve it

**/

static void setXsection(o2::dataformats::MCEventHeader* head, double val) { head->putInfo<double>("Xsection", val); };

static double getXsection(o2::dataformats::MCEventHeader* head, bool& isvalid) { return head->getInfo<double>("Xsection", isvalid); };

static void setXsectionErr(o2::dataformats::MCEventHeader* head, double val) { head->putInfo<double>("Xsection_err", val); };

static double getXsectionErr(o2::dataformats::MCEventHeader* head, bool& isvalid) { return head->getInfo<double>("Xsection_err", isvalid); };

static void setNmpi(o2::dataformats::MCEventHeader* head, int val) { head->putInfo<int>("Nmpi", val); };

static int getNmpi(o2::dataformats::MCEventHeader* head, bool& isvalid) { return head->getInfo<int>("Nmpi", isvalid); };

private:

void updateHeader(o2::dataformats::MCEventHeader* head) final {

// call original function

o2::eventgen::GeneratorPythia8::updateHeader(head);

// store cross-section and Nmpi

setXsection(head, mPythia.info.sigmaGen());

setXsectionErr(head, mPythia.info.sigmaErr());

setNmpi(head, mPythia.info.nMPI());

};

};

FairGenerator*

generator()

{

return new Generator;

}