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Reference Guide
rf903_numintcache.C File Reference

Detailed Description

View in nbviewer Open in SWAN 'NUMERIC ALGORITHM TUNING' RooFit tutorial macro #903

Caching of slow numeric integrals and parameterization of slow numeric integrals



Processing /mnt/build/workspace/root-makedoc-v608/rootspi/rdoc/src/v6-08-00-patches/tutorials/roofit/rf903_numintcache.C...
#include "RooRealVar.h"
#include "RooDataSet.h"
#include "RooDataHist.h"
#include "RooGaussian.h"
#include "RooConstVar.h"
#include "TCanvas.h"
#include "TAxis.h"
#include "RooPlot.h"
#include "RooWorkspace.h"
#include "TFile.h"
#include "TH1.h"
using namespace RooFit;
RooWorkspace* getWorkspace(Int_t mode) ;
void rf903_numintcache(Int_t mode=0)
{
// Mode = 0 : Run plain fit (slow)
// Mode = 1 : Generate workspace with pre-calculated integral and store it on file (prepare for accelerated running)
// Mode = 2 : Run fit from previously stored workspace including cached integrals (fast, requires run in mode=1 first)
// C r e a t e , s a v e o r l o a d w o r k s p a c e w i t h p . d . f .
// -----------------------------------------------------------------------------------
// Make/load workspace, exit here in mode 1
RooWorkspace* w1 = getWorkspace(mode) ;
if (mode==1) {
// Show workspace that was created
w1->Print() ;
// Show plot of cached integral values
if (hhcache) {
new TCanvas("rf903_numintcache","rf903_numintcache",600,600) ;
hhcache->createHistogram("a")->Draw() ;
}
else {
Error("rf903_numintcache","Cached histogram is not existing in workspace");
}
}
// U s e p . d . f . f r o m w o r k s p a c e f o r g e n e r a t i o n a n d f i t t i n g
// -----------------------------------------------------------------------------------
// This is always slow (need to find maximum function value empirically in 3D space)
RooDataSet* d = w1->pdf("model")->generate(RooArgSet(*w1->var("x"),*w1->var("y"),*w1->var("z")),1000) ;
// This is slow in mode 0, but fast in mode 1
w1->pdf("model")->fitTo(*d,Verbose(kTRUE),Timer(kTRUE)) ;
// Projection on x (always slow as 2D integral over Y,Z at fitted value of a is not cached)
RooPlot* framex = w1->var("x")->frame(Title("Projection of 3D model on X")) ;
d->plotOn(framex) ;
w1->pdf("model")->plotOn(framex) ;
// Draw x projection on canvas
new TCanvas("rf903_numintcache","rf903_numintcache",600,600) ;
framex->Draw() ;
// Make workspace available on command line after macro finishes
gDirectory->Add(w1) ;
}
RooWorkspace* getWorkspace(Int_t mode)
{
// C r e a t e , s a v e o r l o a d w o r k s p a c e w i t h p . d . f .
// -----------------------------------------------------------------------------------
//
// Mode = 0 : Create workspace for plain running (no integral caching)
// Mode = 1 : Generate workspace with pre-calculated integral and store it on file
// Mode = 2 : Load previously stored workspace from file
RooWorkspace* w(0) ;
if (mode!=2) {
// Create empty workspace workspace
w = new RooWorkspace("w",1) ;
// Make a difficult to normalize p.d.f. in 3 dimensions that is integrated numerically.
w->factory("EXPR::model('1/((x-a)*(x-a)+0.01)+1/((y-a)*(y-a)+0.01)+1/((z-a)*(z-a)+0.01)',x[-1,1],y[-1,1],z[-1,1],a[-5,5])") ;
}
if (mode==1) {
// Instruct model to pre-calculate normalization integral that integrate at least
// two dimensions numerically. In this specific case the integral value for
// all values of parameter 'a' are stored in a histogram and available for use
// in subsequent fitting and plotting operations (interpolation is applied)
// w->pdf("model")->setNormValueCaching(3) ;
w->pdf("model")->setStringAttribute("CACHEPARMINT","x:y:z");
// Evaluate p.d.f. once to trigger filling of cache
RooArgSet normSet(*w->var("x"),*w->var("y"),*w->var("z")) ;
w->pdf("model")->getVal(&normSet) ;
w->writeToFile("rf903_numintcache.root") ;
}
if (mode==2) {
// Load preexisting workspace from file in mode==2
TFile* f = new TFile("rf903_numintcache.root") ;
w = (RooWorkspace*) f->Get("w") ;
}
// Return created or loaded workspace
return w ;
}
Author
07/2008 - Wouter Verkerke

Definition in file rf903_numintcache.C.