HLTScalersClient.cc

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//
// Revision 1.19  2010/07/20 02:58:27  wmtan
// Add missing #include files
//
// Revision 1.18  2010/04/02 20:48:12  wittich
// updates to scale entries by received number of FU's
//
// Revision 1.17  2010/03/17 20:56:19  wittich
// Check for good updates based on mergeCount values
// add code for rates normalized per FU
//
// Revision 1.16  2010/03/16 22:19:19  wittich
// updates for per-LS normalization for variable
// number of FU's sending information back to the clients.
//
// Revision 1.15  2010/02/11 23:55:18  wittich
// - adapt to shorter Lumi Section length
// - fix bug in how history of counts was filled
//
// Revision 1.14  2010/02/02 11:44:20  wittich
// more diagnostics for online scalers
//
// Revision 1.13  2009/12/15 20:41:16  wittich
// better hlt scalers client
//
// Revision 1.12  2009/11/22 13:33:05  puigh
// clean beginJob
//
// Revision 1.11  2009/11/07 03:35:05  lorenzo
// fixed binning
//
// Revision 1.10  2009/11/04 06:00:05  lorenzo
// changed folders
//
 
 
#include <cassert>
#include <numeric>
 
#include "DQM/TrigXMonitorClient/interface/HLTScalersClient.h"
 
#include "FWCore/Framework/interface/Event.h"
#include "FWCore/Framework/interface/LuminosityBlock.h"
#include "FWCore/Framework/interface/Run.h"
#include "FWCore/MessageLogger/interface/MessageLogger.h"
#include "FWCore/ParameterSet/interface/ParameterSet.h"
#include "FWCore/ServiceRegistry/interface/Service.h"
#include "FWCore/Utilities/interface/isFinite.h"
 
#include "DQMServices/Core/interface/DQMStore.h"
 
using edm::LogInfo;
using edm::LogWarning;
 
// I am not sure this is right at more than 10%
#define SECS_PER_LUMI_SECTION 23.31
const int kPerHisto = 20;
 
HLTScalersClient::HLTScalersClient(const edm::ParameterSet &ps)
    : dbe_(nullptr),
      nLumi_(0),
      currentRate_(nullptr),
      currentLumiBlockNumber_(0),
      first_(true),
      missingPathNames_(true),
      folderName_(ps.getUntrackedParameter<std::string>("dqmFolder", "HLT/HLScalers_EvF")),
      kRateIntegWindow_(ps.getUntrackedParameter<unsigned int>("rateIntegWindow", 3)),
      processName_(ps.getParameter<std::string>("processName")),
      ignores_(),
      debug_(ps.getUntrackedParameter<bool>("debugDump", false)),
      maxFU_(ps.getUntrackedParameter<unsigned int>("maxFU", false)),
      recentOverallCountsPerLS_(kRateIntegWindow_),
      recentNormedOverallCountsPerLS_(2) {
  LogDebug("HLTScalersClient") << "constructor";
  if (debug_) {
    textfile_.open("debug.txt");
    if (!textfile_) {
      std::cout << "constructor: can't open text file" << std::endl;
    }
  }
  // get back-end interface
  dbe_ = edm::Service<DQMStore>().operator->();
  dbe_->setCurrentFolder(folderName_);
 
  std::string rawdir(folderName_ + "/raw");
  dbe_->setCurrentFolder(rawdir);
  hltRate_ = dbe_->book1D("hltRate", "Overall HLT Accept rate vs LS", MAX_LUMI_SEG_HLT, -0.5, MAX_LUMI_SEG_HLT - 0.5);
  dbe_->setCurrentFolder(folderName_);
  hltNormRate_ = dbe_->book1D(
      "hltRateNorm", "Overall HLT Accept rate vs LS, scaled", MAX_LUMI_SEG_HLT, -0.5, MAX_LUMI_SEG_HLT - 0.5);
  hltCount_ = dbe_->book1D("hltCount", "Overall HLT Counts vs LS", MAX_LUMI_SEG_HLT, -0.5, MAX_LUMI_SEG_HLT - 0.5);
  //   hltCountN_= dbe_->book1D("hltCountN", "Overall HLT Counts per LS vs LS",
  //              MAX_LUMI_SEG_HLT, -0.5, MAX_LUMI_SEG_HLT-0.5);
  mergeCount_ =
      dbe_->book1D("mergeCount", "Number of merge counts vs LS", MAX_LUMI_SEG_HLT, -0.5, MAX_LUMI_SEG_HLT - 0.5);
 
  updates_ = dbe_->book1D("updates", "Status of Updates", 2, 0, 2);
  updates_->setBinLabel(1, "Good Updates");
  updates_->setBinLabel(2, "Incomplete Updates");
 
}  // end constructor
 
void HLTScalersClient::beginJob(void) {
  LogDebug("HLTScalersClient") << "beingJob";
  if (dbe_) {
    dbe_->setCurrentFolder(folderName_);
  }
  first_ = true;
  missingPathNames_ = true;
}
 
void HLTScalersClient::beginRun(const edm::Run &run, const edm::EventSetup &c) {
  missingPathNames_ = true;
  first_ = true;
  LogDebug("HLTScalersClient") << "beginRun, run " << run.id();
 
}  // beginRun
 
void HLTScalersClient::endRun(const edm::Run &run, const edm::EventSetup &c) {
  missingPathNames_ = true;
  first_ = true;
}
 
void HLTScalersClient::endLuminosityBlock(const edm::LuminosityBlock &lumiSeg, const edm::EventSetup &c) {
  nLumi_ = lumiSeg.id().luminosityBlock();
 
  // get raw data
  std::string scalHisto = folderName_ + "/raw/hltScalers";
  MonitorElement *scalers = dbe_->get(scalHisto);
  if (scalers == nullptr) {
    LogDebug("HLTScalersClient") << "cannot get hlt scalers histogram, "
                                 << "bailing out.";
    if (debug_)
      std::cout << "No scalers ? Looking for " << scalHisto << std::endl;
    return;
  }
 
  int npaths = scalers->getNbinsX();
  if (npaths > MAX_PATHS)
    npaths = MAX_PATHS;  // HARD CODE FOR NOW
  LogDebug("HLTScalersClient") << "I see " << npaths << " paths. ";
 
  // set the bin labels on the first go-through
  // I need to do this here because we don't have the paths yet
  // on begin-run. I should do this in a less ugly way (see FV?)
  if (first_) {
    std::string rawdir(folderName_ + "/raw");
 
    LogDebug("HLTScalersClient") << "Setting up paths on first endLumiBlock " << npaths;
    dbe_->setCurrentFolder(rawdir);
    currentRate_ = dbe_->book1D("cur_rate", "current lumi section rate per path", npaths, -0.5, npaths - 0.5);
    currentNormRate_ =
        dbe_->book1D("cur_rate_norm", "current norm. lumi section rate per path", npaths, -0.5, npaths - 0.5);
    recentPathCountsPerLS_.reserve(npaths);
    recentNormedPathCountsPerLS_.reserve(npaths);
    char rates_subfolder[256];
    snprintf(rates_subfolder, 256, "%s/RateHistory", folderName_.c_str());
    char counts_subfolder[256];
    snprintf(counts_subfolder, 256, "%s/CountHistory", folderName_.c_str());
 
    hltCurrentRate_.reserve(npaths);
    rateHistories_.reserve(npaths);
    countHistories_.reserve(npaths);
    hltCurrentNormRate_.reserve(npaths);
    rateNormHistories_.reserve(npaths);
 
    dbe_->setCurrentFolder(folderName_);  // these belong in top-level
    for (int i = 0; i < npaths; ++i) {
      dbe_->setCurrentFolder(std::string(rates_subfolder) + "/raw");
 
      char name[256];
      snprintf(name, 256, "raw_rate_p%03d", i);
      //     LogDebug("HLTScalersClient") << "name " << i << " is " << name ;
      rateHistories_.push_back(dbe_->book1D(name, name, MAX_LUMI_SEG_HLT, -0.5, MAX_LUMI_SEG_HLT - 0.5));
      snprintf(name, 256, "norm_rate_p%03d", i);
      dbe_->setCurrentFolder(rates_subfolder);
      rateNormHistories_.push_back(dbe_->book1D(name, name, MAX_LUMI_SEG_HLT, -0.5, MAX_LUMI_SEG_HLT - 0.5));
      dbe_->setCurrentFolder(counts_subfolder);
      snprintf(name, 256, "counts_p%03d", i);
      countHistories_.push_back(dbe_->book1D(name, name, MAX_LUMI_SEG_HLT, -0.5, MAX_LUMI_SEG_HLT - 0.5));
      // prefill the data structures
      recentPathCountsPerLS_.push_back(CountLSFifo_t(kRateIntegWindow_));
      recentNormedPathCountsPerLS_.push_back(CountLSFifo_t(2));
    }
    dbe_->setCurrentFolder(folderName_);
 
    // split hlt scalers up into groups of 20
    const int maxlen = 64;
    char metitle[maxlen];                     // histo name
    char mename[maxlen];                      // ME name
    int numHistos = int(npaths / kPerHisto);  // this hasta be w/o remainders
 
    int remainder = npaths % kPerHisto;
    if (remainder)
      numHistos += 1;
 
    for (int k = 0; k < numHistos; k++) {
      int npath_low = kPerHisto * k;
      int npath_high = kPerHisto * (k + 1) - 1;
      snprintf(mename, maxlen, "hltScalers_%0d", k);
      snprintf(metitle, maxlen, "HLT scalers - Paths %d to %d", npath_low, npath_high);
      dbe_->setCurrentFolder(rawdir);
      hltCurrentRate_.push_back(dbe_->book1D(mename, metitle, kPerHisto, -0.5 + npath_low, npath_high + 0.5));
      dbe_->setCurrentFolder(folderName_);  // these belong in top-level
      snprintf(mename, maxlen, "hltScalersNorm_%0d", k);
      snprintf(metitle, maxlen, "HLT Rate (scaled) - Paths %d to %d", npath_low, npath_high);
      hltCurrentNormRate_.push_back(dbe_->book1D(mename, metitle, kPerHisto, -0.5 + npath_low, npath_high + 0.5));
    }
 
    first_ = false;
  }
 
  if (missingPathNames_) {
    // first try the scalers histogram and see if the bin names are set
    for (int i = 0; i < npaths; ++i) {
      // needs to be i+1 since root bins start at 1
      const char *name = scalers->getTH1()->GetXaxis()->GetBinLabel(i + 1);
      if (name && (strlen(name) > 0)) {
        if (debug_) {
          std::cout << "path " << i << " name is " << name << std::endl;
        }
        int whichHisto = i / kPerHisto;
        int whichBin = i % kPerHisto + 1;
        char pname[256];
        hltCurrentRate_[whichHisto]->setBinLabel(whichBin, name);
        hltCurrentNormRate_[whichHisto]->setBinLabel(whichBin, name);
        snprintf(pname, 256, "Rate - path %s (Path # %03d)", name, i);
        rateHistories_[i]->setTitle(pname);
        rateNormHistories_[i]->setTitle(pname);
        snprintf(pname, 256, "Counts - path %s (Path # %03d)", name, i);
        countHistories_[i]->setTitle(pname);
 
        currentRate_->setBinLabel(i + 1, name);
        currentNormRate_->setBinLabel(i + 1, name);
 
        missingPathNames_ = false;
      }
    }
  }
  // MEGA-HACK
  if (missingPathNames_) {
    // if that didn't work we load 'em from a text file. damn straight.
    int ipath = 1;
    std::ifstream names("names.dat");
    if (!names) {
      if (debug_) {
        std::ostringstream msg;
        msg << "open of "
            << "names.dat";
        perror(msg.str().c_str());
      }
    } else {  // open succeeded
      missingPathNames_ = false;
      std::string line;
      while (!names.eof()) {
        getline(names, line);
        std::istringstream fnames(line);
        std::string label;
        int bin;
        if (fnames.str().find('#') == 0)  // skip comment lines
          continue;
        if (fnames >> bin >> label) {
          if (debug_) {
            std::cout << bin << "--" << label << "(" << ipath << ")" << std::endl;
          }
          currentRate_->setBinLabel(ipath, label);
          currentNormRate_->setBinLabel(ipath, label);
          countHistories_[ipath - 1]->setTitle(label);
          rateHistories_[ipath - 1]->setTitle(label);
          rateNormHistories_[ipath - 1]->setTitle(label);
          int whichHisto = (ipath - 1) / kPerHisto;
          int whichBin = (ipath - 1) % kPerHisto + 1;
          hltCurrentRate_[whichHisto]->setBinLabel(whichBin, label);
          hltCurrentNormRate_[whichHisto]->setBinLabel(whichBin, label);
          ++ipath;
          if (ipath > npaths)
            break;
        }  //
      }    // loop lines
    }      // open ok
  }
 
  // END SETUP
 
  std::string nLumiHisto(folderName_ + "/nLumiBlock");
  MonitorElement *nLumi = dbe_->get(nLumiHisto);
  if (nLumi == nullptr) {
    nLumiHisto = folderName_ + "/raw/nLumiBlock";
    nLumi = dbe_->get(nLumiHisto);
  }
  int testval = (nLumi != nullptr ? nLumi->getIntValue() : -1);
  LogDebug("HLTScalersClient") << "Lumi Block from DQM: " << testval << ", local is " << nLumi_;
  int nL = (nLumi != nullptr ? nLumi->getIntValue() : nLumi_);
  if (nL > MAX_LUMI_SEG_HLT) {
    LogDebug("HLTScalersClient") << "Too many Lumi segments, " << nL << " is greater than MAX_LUMI_SEG_HLT,"
                                 << " wrapping to " << (nL % MAX_LUMI_SEG_HLT);
    // nL = MAX_LUMI_SEG_HLT;
    nL = nL % MAX_LUMI_SEG_HLT;
  }
 
  // merging counts
  double num_fu = -1.0;
  std::string mergeName(folderName_ + "/raw/hltMerge");
  MonitorElement *merge = dbe_->get(mergeName);
  if (merge != nullptr) {
    num_fu = merge->getBinContent(1);
    if (debug_) {
      std::cout << "Number of received entries: " << num_fu << std::endl;
    }
    mergeCount_->Fill(nL, num_fu);
  }
  // end
 
  // evaluate the data
  // loop over current counts
 
  // this gets filled for all times. Mainly for debugging.
  for (int i = 1; i <= npaths; ++i) {  // bins start at 1
    double current_count = scalers->getBinContent(i);
    // nb that this will now _overwrite_ some settings
    countHistories_[i - 1]->setBinContent(nL, current_count);  // good or bad
  }
 
  std::string overallScalerName(folderName_ + "/raw/hltOverallScaler");
  MonitorElement *hltScaler = dbe_->get(overallScalerName);
  if (hltScaler != nullptr) {
    double current_count = hltScaler->getBinContent(1);
    hltCount_->setBinContent(nL, current_count);
    recentOverallCountsPerLS_.update(CountLS_t(nL, current_count));
    std::pair<double, double> sl = getSlope_(recentOverallCountsPerLS_);
    double slope = sl.first;
    double slope_err = sl.second;
    if (slope > 0) {
      hltRate_->setBinContent(nL, slope);
      if (!edm::isNotFinite(slope_err) && (slope_err >= 0))
        hltRate_->setBinError(nL, slope_err);
    }
  }  // found  histo
 
  if (num_fu >= 0.95 * maxFU_) {
    if (num_fu > maxFU_) {
      maxFU_ = num_fu;
      if (debug_)
        std::cout << "maxFU is now " << maxFU_ << std::endl;
    }
    // good data
    for (int i = 1; i <= npaths; ++i) {  // bins start at 1
      double current_count = scalers->getBinContent(i);
      // DEBUG
      if (!recentPathCountsPerLS_[i - 1].empty() && debug_)
        std::cout << i << "\t-> good one: new => cnt, ls = " << current_count << ", " << nL
                  << ", old = " << recentPathCountsPerLS_[i - 1].back().second << "\t"
                  << recentPathCountsPerLS_[i - 1].back().first << std::endl;
      // END DEBUG
      recentPathCountsPerLS_[i - 1].update(CountLS_t(nL, current_count));
 
      // NB: we do not fill a new entry in the rate histo if we can't
      // calculate it
      std::pair<double, double> sl = getSlope_(recentPathCountsPerLS_[i - 1]);
      double slope = sl.first;
      double slope_err = sl.second;
      // rateHistories_[i-1]->Fill(nL,slope);
      if (slope > 0) {
        rateHistories_[i - 1]->setBinContent(nL, slope);
        // set the current rate(s)
        hltCurrentRate_[(i - 1) / kPerHisto]->setBinContent(i % kPerHisto, slope);
        currentRate_->setBinContent(i, slope);
        if (!edm::isNotFinite(slope_err) && (slope_err >= 0)) {
          currentRate_->setBinError(i, slope_err);
          hltCurrentRate_[(i - 1) / kPerHisto]->setBinError(i % kPerHisto, slope_err);
          rateHistories_[i - 1]->setBinError(nL, slope_err);
        }
      }
 
    }  // loop over paths
 
    // ---------------------------- overall rate, absolute counts
    std::string overallScalerName(folderName_ + "/raw/hltOverallScaler");
    MonitorElement *hltScaler = dbe_->get(overallScalerName);
    if (hltScaler != nullptr) {
      double current_count = hltScaler->getBinContent(1);
      hltCount_->setBinContent(nL, current_count);
      recentOverallCountsPerLS_.update(CountLS_t(nL, current_count));
      std::pair<double, double> sl = getSlope_(recentOverallCountsPerLS_);
      double slope = sl.first;
      double slope_err = sl.second;
      if (slope >= 0) {
        hltRate_->setBinContent(nL, slope);
        if (!edm::isNotFinite(slope_err) && (slope_err >= 0))
          hltRate_->setBinError(nL, slope_err);
      }
    }                   // found  histo
    updates_->Fill(0);  // good
  }                     // check on number of FU's - good data
  else {
    updates_->Fill(1);  // missing updates
  }
 
  // PW DEBUG
  if (debug_) {
    textfile_ << nL << "\t" << npaths << "\t";
    for (int i = 0; i < npaths; ++i) {
      textfile_ << scalers->getBinContent(i) << " ";
    }
    textfile_ << std::endl;
  }
  // end DEBUG
 
#ifdef LATER
  // ------ overall rate normalized - all data
  overallScalerName = std::string(folderName_ + "/raw/hltOverallScalerN");
  hltScaler = dbe_->get(overallScalerName);
  if (hltScaler != 0) {
    double cnt = hltScaler->getBinContent(1);
    //     hltCountN_->setBinContent(nL,cnt);
    if (debug_) {
      std::cout << "Overall Norm: new => cnt, ls = " << cnt << ", " << nL << ", num_fu = " << num_fu << std::endl;
    }
    recentNormedOverallCountsPerLS_.update(CountLS_t(nL, cnt / num_fu));
    cnt = recentNormedOverallCountsPerLS_.getCount(nL);  // for dupes/partials
    double slope = cnt / num_fu / SECS_PER_LUMI_SECTION;
    if (debug_) {
      std::cout << "Normalized slope = " << slope << std::endl;
    }
    if (slope > 0)
      hltNormRate_->setBinContent(nL, slope);
  }
  //
  std::string scalHistoNorm = folderName_ + "/raw/hltScalersN";
  MonitorElement *scalersN = dbe_->get(scalHistoNorm);
  if (scalersN) {
    for (int i = 0; i < npaths; ++i) {
      double cnt = scalersN->getBinContent(i);
      double slope = cnt / num_fu / SECS_PER_LUMI_SECTION;
      if (slope > 0) {
        rateNormHistories_[i - 1]->setBinContent(nL, slope);
        // set the current rate(s)
        hltCurrentNormRate_[(i - 1) / kPerHisto]->setBinContent(i % kPerHisto, slope);
        currentNormRate_->setBinContent(i, slope);
      }
    }
  }
#else  // NOT LATER
  // ------ overall rate normalized - all data
  overallScalerName = std::string(folderName_ + "/raw/hltOverallScaler");
  hltScaler = dbe_->get(overallScalerName);
  if (hltScaler != nullptr) {
    double cnt = hltScaler->getBinContent(1);
    //     hltCountN_->setBinContent(nL,cnt);
    float sf = num_fu / maxFU_;
    if (debug_) {
      std::cout << "Overall Norm: new => cnt, ls = " << cnt << ", " << nL << ", num_fu = " << num_fu << ", sf = " << sf
                << std::endl;
    }
    recentNormedOverallCountsPerLS_.update(CountLS_t(nL, cnt / sf));
    cnt = recentNormedOverallCountsPerLS_.getCount(nL);  // for dupes/partials
    std::pair<double, double> sl = getSlope_(recentNormedOverallCountsPerLS_);
    double slope = sl.first;
    double slope_err = sl.second;
    if (debug_) {
      std::cout << "Normalized slope = " << slope << std::endl;
    }
    if (slope > 0) {
      hltNormRate_->setBinContent(nL, slope);
      if (cnt > 0)
        slope_err = slope * sqrt(2. / num_fu + 2. / cnt);
      if (!edm::isNotFinite(slope_err) && (slope_err >= 0))
        hltNormRate_->setBinError(nL, slope_err);
    }
  }
  //
  std::string scalHistoNorm = folderName_ + "/raw/hltScalers";
  MonitorElement *scalersN = dbe_->get(scalHistoNorm);
  if (scalersN) {
    double sf = num_fu / maxFU_;
    for (int i = 1; i <= npaths; ++i) {
      double cnt = scalersN->getBinContent(i);
      recentNormedPathCountsPerLS_[i - 1].update(CountLS_t(nL, cnt / sf));
      std::pair<double, double> sl = getSlope_(recentNormedPathCountsPerLS_[i - 1]);
      double slope = sl.first;
      double slope_err = sl.second;
      if (slope >= 0) {
        rateNormHistories_[i - 1]->setBinContent(nL, slope);
        // set the current rate(s)
        hltCurrentNormRate_[(i - 1) / kPerHisto]->setBinContent(i % kPerHisto, slope);
        currentNormRate_->setBinContent(i, slope);
        if (slope_err <= 0 && cnt > 0) {
          // ignores error on prev point, so scale by sqrt(2)
          slope_err = slope * sqrt(2. / num_fu + 2. / cnt);
          if (debug_) {
            std::cout << "Slope err " << i << " = " << slope_err << std::endl;
          }
        }
        if (!edm::isNotFinite(slope_err) && (slope_err >= 0)) {
          rateNormHistories_[i - 1]->setBinError(nL, slope_err);
          // set the current rate(s)
          hltCurrentNormRate_[(i - 1) / kPerHisto]->setBinError(i % kPerHisto, slope_err);
          currentNormRate_->setBinError(i, slope_err);
        }
      }
    }
  }
 
#endif  // LATER
  //
}
 
// unused
void HLTScalersClient::analyze(const edm::Event &e, const edm::EventSetup &c) {
  // nothing to do here
}
 
// this is probably overkill. Do a least-squares fit to get slope
// note that the data is in units of counts, ls number
// but we return a value in Hz...
std::pair<double, double> HLTScalersClient::getSlope_(const HLTScalersClient::CountLSFifo_t &points) {
  double slope, sigma_m;
  if (points.size() < points.targetSize()) {
    return std::pair<double, double>(-1, -1);
  }
  // just do a delta if we just want two bins
  else if (points.size() == 2) {
    // just do diff and be done with it
    double delta_ls = points.front().first - points.back().first;
    double delta_cnt = points.front().second - points.back().second;
    slope = delta_cnt / delta_ls;
    sigma_m = -1;
  } else {  // do a fit
    double xy = 0;
    double x = 0;
    double xsq = 0;
    double y = 0;
    double n = double(points.size());
    for (auto i(points.begin()); i != points.end(); ++i) {
      if (debug_)
        std::cout << "x = " << i->first << ", y = " << i->second << std::endl;
      xy += i->first * i->second;
      x += i->first;
      xsq += i->first * i->first;
      y += i->second;
    }
    slope = (n * xy - x * y) / (n * xsq - x * x);
 
    // now get the uncertainty on the slope. Need intercept for this.
    double intercept = (xsq * y - xy * x) / (n * xsq - x * x);
    double sigma_ysq = 0;
    for (auto i(points.begin()); i != points.end(); ++i) {
      sigma_ysq += pow((i->second - slope * i->first - intercept), 2.);
    }
    //     if ( debug_ )
    //       std::cout << "chi^2 = " << sigma_ysq << std::endl;
    sigma_ysq *= 1. / (n - 2.);
 
    sigma_m = sqrt(n * sigma_ysq / (n * xsq - x * x));
  }
 
  //  std::cout << "Slope is " << slope << std::endl;
  slope /= SECS_PER_LUMI_SECTION;
  if (sigma_m > 0)
    sigma_m /= SECS_PER_LUMI_SECTION;
  //   if ( debug_ ) {
  //     std::cout << "Slope = " << slope << " +- " << sigma_m
  //          << std::endl;
  //   std::cout << "intercept is " << intercept
  //        << std::endl;
  //  }
 
  return std::pair<double, double>(slope, sigma_m);
}