The Computer Language
Benchmarks Game

spectral-norm Ruby JRuby program

# The Computer Language Benchmarks Game
# http://benchmarksgame.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 = 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
print "%0.9f" % (Math.sqrt(vBv/vv)), "\n"

    

NOTES:
64-bit Ubuntu quad core
jruby 9.1.16.0 (2.3.3) 2018-02-21 8f3f95a Java HotSpot(TM) 64-Bit Server VM 10+46 on 10+46 +jit [linux-x86_64]


Thu, 22 Mar 2018 03:33:57 GMT

MAKE:
mv spectralnorm.jruby spectralnorm.rb

0.10s to complete and log all make actions

COMMAND LINE:
/opt/src/jruby-9.1.16.0/bin/jruby -Xcompile.fastest=true -Xcompile.invokedynamic=true -J-server -J-Xmn512m -J-Xms2048m -J-Xmx2048m spectralnorm.rb 5500

PROGRAM OUTPUT:
1.274224153