doc/v626/rf901__numintconfig_8py.html

from __future__ import print_function

import ROOT


# Adjust global 1D integration precision

# ----------------------------------------------------------------------------


# Print current global default configuration for numeric integration

# strategies

ROOT.RooAbsReal.defaultIntegratorConfig().Print("v")


# Example: Change global precision for 1D integrals from 1e-7 to 1e-6

#

# The relative epsilon (change as fraction of current best integral estimate) and

# absolute epsilon (absolute change w.r.t last best integral estimate) can be specified

# separately. For most pdf integrals the relative change criterium is the most important,

# however for certain non-pdf functions that integrate out to zero a separate absolute

# change criterium is necessary to declare convergence of the integral

#

# NB: ROOT.This change is for illustration only. In general the precision should be at least 1e-7

# for normalization integrals for MINUIT to succeed.

#

ROOT.RooAbsReal.defaultIntegratorConfig().setEpsAbs(1e-6)

ROOT.RooAbsReal.defaultIntegratorConfig().setEpsRel(1e-6)


# N u m e r i c   i n t e g r a t i o n   o f   l a n d a u   p d f

# ------------------------------------------------------------------


# Construct pdf without support for analytical integrator for

# demonstration purposes

x = ROOT.RooRealVar("x", "x", -10, 10)

landau = ROOT.RooLandau("landau", "landau", x, ROOT.RooFit.RooConst(0), ROOT.RooFit.RooConst(0.1))


# Activate debug-level messages for topic integration to be able to follow

# actions below

ROOT.RooMsgService.instance().addStream(ROOT.RooFit.DEBUG, Topic=ROOT.RooFit.Integration)


# Calculate integral over landau with default choice of numeric integrator

intLandau = landau.createIntegral({x})

val = intLandau.getVal()

print(" [1] int_dx landau(x) = ", val)  # setprecision(15)


# Same with custom configuration

# -----------------------------------------------------------


# Construct a custom configuration which uses the adaptive Gauss-Kronrod technique

# for closed 1D integrals

customConfig = ROOT.RooNumIntConfig(ROOT.RooAbsReal.defaultIntegratorConfig())

integratorGKNotExisting = customConfig.method1D().setLabel("RooAdaptiveGaussKronrodIntegrator1D")

if integratorGKNotExisting:

    print("WARNING: RooAdaptiveGaussKronrodIntegrator is not existing because ROOT is built without Mathmore support")


# Calculate integral over landau with custom integral specification

intLandau2 = landau.createIntegral({x}, NumIntConfig=customConfig)

val2 = intLandau2.getVal()

print(" [2] int_dx landau(x) = ", val2)


# Adjusting default config for a specific pdf

# -------------------------------------------------------------------------------------


# Another possibility: associate custom numeric integration configuration

# as default for object 'landau'

landau.setIntegratorConfig(customConfig)


# Calculate integral over landau custom numeric integrator specified as

# object default

intLandau3 = landau.createIntegral({x})

val3 = intLandau3.getVal()

print(" [3] int_dx landau(x) = ", val3)


# Another possibility: Change global default for 1D numeric integration

# strategy on finite domains

if not integratorGKNotExisting:

    ROOT.RooAbsReal.defaultIntegratorConfig().method1D().setLabel("RooAdaptiveGaussKronrodIntegrator1D")


    # Adjusting parameters of a speficic technique

    # ---------------------------------------------------------------------------------------


    # Adjust maximum number of steps of ROOT.RooIntegrator1D in the global

    # default configuration

    ROOT.RooAbsReal.defaultIntegratorConfig().getConfigSection("RooIntegrator1D").setRealValue("maxSteps", 30)


    # Example of how to change the parameters of a numeric integrator

    # (Each config section is a ROOT.RooArgSet with ROOT.RooRealVars holding real-valued parameters

    #  and ROOT.RooCategories holding parameters with a finite set of options)

    customConfig.getConfigSection("RooAdaptiveGaussKronrodIntegrator1D").setRealValue("maxSeg", 50)

    customConfig.getConfigSection("RooAdaptiveGaussKronrodIntegrator1D").setCatLabel("method", "15Points")


    # Example of how to print set of possible values for "method" category

    customConfig.getConfigSection("RooAdaptiveGaussKronrodIntegrator1D").find("method").Print("v")