MAYBE
Input TRS:
      1: a(d(x1)) -> d(b(x1))
      2: a(x1) -> b(b(b(x1)))
      3: d(x1) -> x1
      4: a(x1) -> x1
      5: b(d(b(x1))) -> a(d(x1))
      6: b(c(x1)) -> c(d(d(x1)))
      7: a(c(x1)) -> b(b(c(d(x1))))
Number of strict rules: 7
Direct POLO(bPol) ... failed.
Uncurrying ... failed.
Dependency Pairs:
     #1: #a(x1) -> #b(b(b(x1)))
     #2: #a(x1) -> #b(b(x1))
     #3: #a(x1) -> #b(x1)
     #4: #b(c(x1)) -> #d(d(x1))
     #5: #b(c(x1)) -> #d(x1)
     #6: #a(c(x1)) -> #b(b(c(d(x1))))
     #7: #a(c(x1)) -> #b(c(d(x1)))
     #8: #a(c(x1)) -> #d(x1)
     #9: #b(d(b(x1))) -> #a(d(x1))
     #10: #b(d(b(x1))) -> #d(x1)
     #11: #a(d(x1)) -> #d(b(x1))
     #12: #a(d(x1)) -> #b(x1)
Number of SCCs: 1, DPs: 5
  SCC { #1..3 #9 #12 }
POLO(Sum)... succeeded.
      a 	w: x1
      d 	w: x1 + 21239
      b 	w: x1
      c 	w: 1
      #d 	w: 0
      #a 	w: x1
      #b 	w: x1
    USABLE RULES: { 1..7 }
    Removed DPs: #12
Number of SCCs: 1, DPs: 4
  SCC { #1..3 #9 }
POLO(Sum)... POLO(max)... QLPOS... POLO(mSum)... QWPOpS(mSum)... Mat2b... succeeded.
      a 	w: x1 + [3;3]
      d 	w: [1,1;1,1] * x1 + [1;11677]
      b 	w: x1 + [1;1]
      c 	w: [24498;39812]
      #d 	w: [0;0]
      #a 	w: [0,1;1,0] * x1 + [2;2]
      #b 	w: [0,1;1,0] * x1
    USABLE RULES: { 1..7 }
    Removed DPs: #2 #3
Number of SCCs: 1, DPs: 2
  SCC { #1 #9 }
POLO(Sum)... POLO(max)... QLPOS... POLO(mSum)... QWPOpS(mSum)... Mat2b... failed.
Finding a loop...  failed.