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SUMMARY:CANCELLED -- The complexity of counting problems - David Richerby\
 , University of Essex
DTSTART:20220218T140000Z
DTEND:20220218T150000Z
UID:TALK169202@talks.cam.ac.uk
CONTACT:Jamie Vicary
DESCRIPTION:**TALK CANCELLED DUE TO STORM EUNICE**\n\nEvery computational 
 decision problem ("Is there an X?") has a natural counting variant ("How m
 any X's are there?"). More generally\, computing weighted sums such as int
 egrals\, expectations and partition functions in statistical physics can a
 lso be seen as counting problems.\n\nI will give an introduction to the co
 mplexity of solving counting problems. I will focus on variants of constra
 int satisfaction problems (CSPs) and exactly counting the solutions\, thou
 gh I'll also touch on approximate counting. CSPs are powerful enough to na
 turally express many important problems\, but also being restricted enough
  to allow their computational complexity to be classified completely and e
 legantly.
LOCATION:FW26
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