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        <article-title>Optimization is Hard, but Hillclimbing is Easy { Right?</article-title>
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      <contrib-group>
        <aff id="aff0">
          <label>0</label>
          <institution>Johannes Lengler Institute of Theoretical Computer Science Department of Computer Science ETH Zurich</institution>
          ,
          <addr-line>Switzerland https://</addr-line>
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        <kwd>Optimization</kwd>
        <kwd>Hillclimbing</kwd>
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      <p>Hillclimbing is an integral part of every optimization algorithm. One
would expect that our standard hillclimbing algorithms can solve nice,
unimodal functions e ciently. For example, strictly monotone
functions: consider the search space S = f0; 1gn of n-bit strings; then
a strictly monotone function f : S ! R is a function that satis es
f (x) &lt; f (y) for all di erent strings x, y in S such that xi yi holds
for all 1 i n. Strictly montone functions are the easiest imaginable
testbed for hillclimbers: The function f always prefers one-bits over
zero-bits, so there are always short and clearly labelled paths from any
start point to the unique global optimum 11::1. Surprisingly, it has
become clear in the last years that many of our standard hillclimbers
fail miserably on some strictly monotone functions. In many instances,
they need exponential time to nd the optimum. This devastating
result has deepened our understanding of hillclimbing techniques, and
has given new insights into the mechanisms that are behind some
hillclimbing techniques, like selective pressure, step size policies, and
population e ects. These insights have also improved our understanding
of optimization beyond hillclimbing, in particular of optimization in
dynamic environments.</p>
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