ceta_eq: termination proof not accepted
1: error below switch to dependency pairs
1.1: error below the dependency graph processor
 1.1.1: error when applying the reduction pair processor with usable rules to remove from the DP problem
  pairs:
  
  f#(s(x), 0, z, u) -> f#(x, u, minus(z, s(x)), u)
  f#(s(x), s(y), z, u) -> f#(x, u, z, u)
  rules:
  
  f(0, y, 0, u) -> true
  f(0, y, s(z), u) -> false
  f(s(x), 0, z, u) -> f(x, u, minus(z, s(x)), u)
  f(s(x), s(y), z, u) -> if(le(x, y), f(s(x), minus(y, x), z, u), f(x, u, z, u))
  perfectp(0) -> false
  perfectp(s(x)) -> f(x, s(0), s(x), s(x))
  
   the pairs 
  f#(s(x), 0, z, u) -> f#(x, u, minus(z, s(x)), u)
  f#(s(x), s(y), z, u) -> f#(x, u, z, u)
  
  could not apply the generic root reduction pair processor with the following
  SCNP-version with mu = MS and the level mapping defined by 
  pi(f#) = [(epsilon,0),(1,0),(4,0)]
  Argument Filter: 
  pi(f#/4) = 3
  pi(s/1) = [1]
  pi(0/0) = []
  pi(minus/2) = []
  
  RPO with the following precedence
  precedence(s[1]) = 0
  precedence(0[0]) = 1
  precedence(minus[2]) = 0
  
  precedence(_) = 0
  and the following status
  status(s[1]) = lex
  status(0[0]) = lex
  status(minus[2]) = lex
  
  status(_) = lex
  
  problem when orienting DPs
  cannot orient pair f#(s(x), s(y), z, u) -> f#(x, u, z, u) strictly:
  [(f#(s(x), s(y), z, u),0),(s(x),0),(u,0)] >mu [(f#(x, u, z, u),0),(x,0),(u,0)] could not be ensured