The Computer Language
Benchmarks Game

spectral-norm Node.js #3 program

source code

// The Computer Language Benchmarks Game
// http://benchmarksgame.alioth.debian.org/
//
// contributed by Ian Osgood
// Optimized by Roy Williams
// modified for Node.js by Isaac Gouy 

function A(i,j) {
  return 1/(((i+j)*(i+j+1)>>>1)+i+1);
}

function Au(u,v) {
    var n = u.length;
  for (var i=0; i<n; ++i) {
    var t = 0;
    for (var j=0; j<n; ++j)
      t += A(i,j) * u[j];
    v[i] = t;
  }
}

function Atu(u,v) {
  var n = u.length;
  for (var i=0; i<n; ++i) {
    var t = 0;
    for (var j=0; j<n; ++j)
      t += A(j,i) * u[j];
    v[i] = t;
  }
}

function AtAu(u,v,w) {
  Au(u,w);
  Atu(w,v);
}

function spectralnorm(n) {
  var storage_ = new ArrayBuffer(n * 24);
  var u = new Float64Array(storage_, 0, n),
      v = new Float64Array(storage_, 8*n, n),
      w = new Float64Array(storage_, 16*n, n);
  var i, vv=0, vBv=0;
  for (i=0; i<n; ++i) {
    u[i] = 1; v[i] = w[i] = 0; 
  }
  for (i=0; i<10; ++i) {
    AtAu(u,v,w);
    AtAu(v,u,w);
  }
  for (i=0; i<n; ++i) {
    vBv += u[i]*v[i];
    vv  += v[i]*v[i];
  }
  return Math.sqrt(vBv/vv);
}

console.log(spectralnorm(+process.argv[2]).toFixed(9));
    

notes, command-line, and program output

NOTES:
64-bit Ubuntu quad core
v7.6.0


Wed, 22 Feb 2017 21:23:41 GMT

MAKE:
cp -L spectralnorm.node-3.node spectralnorm.node-3.js
0.01s to complete and log all make actions

COMMAND LINE:
/usr/local/src/node-v7.6.0-linux-x64/bin/node spectralnorm.node-3.js 5500

PROGRAM OUTPUT:
1.274224153