1 files changed, 50 insertions, 0 deletions
diff --git a/benchmark/bm_so_spectralnorm.rb b/benchmark/bm_so_spectralnorm.rb
new file mode 100644
index 0000000000..3617da5236
--- /dev/null
+++ b/benchmark/bm_so_spectralnorm.rb
@@ -0,0 +1,50 @@
+# The Computer Language Shootout
+# http://shootout.alioth.debian.org/
+# Contributed by Sokolov Yura
+
+def eval_A(i,j)
+	return 1.0/((i+j)*(i+j+1)/2+i+1)
+end
+
+def eval_A_times_u(u)
+        v, i = nil, nil
+	(0..u.length-1).collect { |i|
+                v = 0
+		for j in 0..u.length-1
+			v += eval_A(i,j)*u[j]
+                end
+                v
+        }
+end
+
+def eval_At_times_u(u)
+	v, i = nil, nil
+	(0..u.length-1).collect{|i|
+                v = 0
+		for j in 0..u.length-1
+			v += eval_A(j,i)*u[j]
+                end
+                v
+        }
+end
+
+def eval_AtA_times_u(u)
+	return eval_At_times_u(eval_A_times_u(u))
+end
+
+n = 500 # ARGV[0].to_i
+
+u=[1]*n
+for i in 1..10
+        v=eval_AtA_times_u(u)
+        u=eval_AtA_times_u(v)
+end
+vBv=0
+vv=0
+for i in 0..n-1
+        vBv += u[i]*v[i]
+        vv += v[i]*v[i]
+end
+
+str = "%0.9f" % (Math.sqrt(vBv/vv)), "\n"
+# print str