From 2f04e5647ca1889cdd5da731dfc9f15138212def Mon Sep 17 00:00:00 2001
From: Patrick Simianer <p@simianer.de>
Date: Wed, 5 Jul 2017 07:53:33 +0200
Subject: ranking

---
 algorithms/ranking-dist.rb | 75 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 75 insertions(+)
 create mode 100755 algorithms/ranking-dist.rb

diff --git a/algorithms/ranking-dist.rb b/algorithms/ranking-dist.rb
new file mode 100755
index 0000000..c621bdd
--- /dev/null
+++ b/algorithms/ranking-dist.rb
@@ -0,0 +1,75 @@
+#!/usr/bin/env ruby
+
+items  = [0, 1, 2] 
+ranks  = [1, 2, 3]
+#permutations = [
+#  [1,2,3],
+#  [2,3,1],
+#  [3,1,2],
+#  [3,2,1],
+#  [1,3,2]
+#]
+scores = [3, 2, 1]
+
+def f items, ranks, scores,topone=false
+  prod = 1
+  items.each_with_index { |i,j|
+    x = []
+    d = Math.exp(scores[ranks[i]-1])
+    x << ranks[i]
+    sum = 0
+    if j+1 <= items.size
+      (j).upto(items.size-1) { |k|
+        sum = sum+Math.exp(scores[ranks[k]-1])
+        x << ranks[k]
+      }
+      prod = prod*(d/sum)
+      if topone
+        return  prod
+      end
+      puts "#{ranks[i]} / #{x[1..-1].map { |z| "#{z}" }.join(" ")}"
+    end
+  }
+  return prod
+end
+
+#best = f items,ranks,scores
+
+permutations = {}
+sz = 0
+stop = 0
+while true
+  break if stop == 1000
+  r = ranks.shuffle
+  permutations[r] = 1
+  if sz == permutations.size
+    stop = stop+1
+  else
+    sz = permutations.size
+    stop = 0
+  end
+end
+
+puts permutations.to_s
+
+sumtoone = 0
+permutations.each_key { |r|
+  p = f items,r,scores,false
+  puts "#{r.to_s} #{p}"
+  puts
+  sumtoone = sumtoone+p
+  #if p >= best
+  #  puts r.to_s
+  #  puts p
+  #end
+}
+
+puts "==="
+puts sumtoone
+
+puts "+++ NLL"
+
+scores = [0.1,0.1,100]
+true_ranking = [2,1,3]
+puts(-Math.log(f(items,true_ranking,scores)))
+
-- 
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