Rf 9 0 3_Numintcache¶

Numeric algorithm tuning: caching of slow numeric integrals and parameterizations of slow numeric integrals

Author: Clemens Lange, Wouter Verkerke (C++ version)
This notebook tutorial was automatically generated with ROOTBOOK-izer from the macro found in the ROOT repository on Monday, January 17, 2022 at 10:21 AM.

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import sys
import ROOT

def getWorkspace(mode):
# Create, save or load workspace with pdf
# -----------------------------------------------------------------------------------
#
# Mode = 0 : Create workspace for plain running (no integral caching)
# Mode = 1 : Generate workspace with precalculated integral and store it on file
# Mode = 2 : Load previously stored workspace from file

w = ROOT.RooWorkspace()

if mode != 2:
# Create empty workspace workspace
w = ROOT.RooWorkspace("w", 1)

# Make a difficult to normalize  pdf 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 precalculate normalization integral that integrate at least
# two dimensions numerically. In self 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)
model = w["model"]
model.setStringAttribute("CACHEPARMINT", "x:y:z")

# Evaluate pdf once to trigger filling of cache
normSet = {w["x"], w["y"], w["z"]}
model.getVal(normSet)
w.writeToFile("rf903_numintcache.root")

if mode == 2:
# Load preexisting workspace from file in mode==2
f = ROOT.TFile("rf903_numintcache.root")
w = f.Get("w")

# Return created or loaded workspace
return w

mode = 0

Mode = 0 : Run plain fit (slow) Mode = 1 : Generate workspace with precalculated integral and store it on file (prepare for accelerated running) Mode = 2 : Run fit from previously stored workspace including cached integrals (fast, run in mode=1 first)

Create, save or load workspace with pdf¶

Make/load workspace, here in mode 1

In [ ]:
w = getWorkspace(mode)
if mode == 1:
# Show workspace that was created
w.Print()

# Show plot of cached integral values
hhcache = w.expensiveObjectCache().getObj(1)
if hhcache:
ROOT.TCanvas("rf903_numintcache", "rf903_numintcache", 600, 600)
hhcache.createHistogram("a").Draw()
else:
ROOT.RooFit.Error("rf903_numintcache", "Cached histogram is not existing in workspace")
sys.exit()

Use pdf from workspace for generation and fitting¶

ROOT.This is always slow (need to find maximum function value empirically in 3D space)

In [ ]:
model = w["model"]
d = model.generate({w["x"], w["y"], w["z"]}, 1000)

ROOT.This is slow in mode 0, fast in mode 1

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model.fitTo(d, Verbose=True, Timer=True)

Projection on x (always slow as 2D integral over Y, at fitted value of a is not cached)

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framex = w["x"].frame(Title="Projection of 3D model on X")
d.plotOn(framex)
model.plotOn(framex)

Draw x projection on canvas

In [ ]:
c = ROOT.TCanvas("rf903_numintcache", "rf903_numintcache", 600, 600)
framex.Draw()

c.SaveAs("rf903_numintcache.png")

Make workspace available on command line after macro finishes

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