Result contains NaN for some matrices

[hasanbalci]

I am considering to use your implementation, but during testing I realized that the result (especially u and q) of some matrices contains NaN values.

Some examples are:

input: [[-896, -896], [-19, -19]] output: u = [[NaN, NaN], [NaN, NaN]] q = [0, NaN] v = [[0.7071067811865476, -0.7071067811865475], [-0.7071067811865474, -0.7071067811865475]]

input: [[0, 0],[-1560.116, -2789.99]] output: u = [[NaN, NaN], [NaN, NaN]] q = [0, NaN] v = [[0.8728097060016351, -0.48806066949646665], [-0.48806066949646654, -0.8728097060016349]]

Thanks!

[DamianCz]

There are some divided by zero in implementation I can provide fix @danilosalvati if you want.

[danilosalvati]

Sorry @hasanbalci I completely forgot to answer your issue... At a first look it seem your bug is caused from eps parameter... I tried with runkit your first example with Number.MIN_VALUE as eps and it works

const svdJs = require("svd-js")
const a = [[-896, -896], [-19, -19]]
const { u, v, q } = svdJs.SVD(a, true, true, 1e-15)
console.log(u)
console.log(v)
console.log(q)

// output:
// [[0.02120059107367143, -0.9997752422110318], [-0.9997752422110316,0.021200591073671428]]
// [[-0.7071067811865475, 0.7071067811865476], [0.7071067811865475, 0.7071067811865474]]
// [0, 1267.4202144513872]

@DamianCz Where did you found those divided by zero in the implementation? Anyway PRs are always welcome :smile:

[hasanbalci]

@danilosalvati It seems that adding eps parameter as 1e-15 is working in my first example but not in the second one.

[DamianCz]

@danilosalvati it is safe to check all divided places . I will add PR when I will find time

[pygabc1]

There are some divided by zero in implementation I can provide fix @danilosalvati if you want.

Hi, DamianCz, did you fix "ZeroDivisionError: float division by zero"? Many lines occurred these problems, and it might result in the left singular vector(matrix) with "all zero components". For example, for c = f/z , I modified to c = (f/z if z != 0 else 0) (for python)

[DamianCz]

@pygabc1 I have added function and replace all usage of / with this function. Will add PR this week.

function dividedValue(divident, divisor) {
        if (divisor === 0) {
            return 0;
        }

        return divident / divisor;
    }

[jee7]

Did this ever get fixed? I have the same issue right now with version 1.1.1.

var result = SVDJS.SVD([
    [1, 2, 3],
    [2, 4, 6],
    [3, 6, 9],
], true, true, 1e-15);

The expected output for q would be [14, 0, 0], but I'm getting [0, NaN, 0] instead.

I tried the solution that replaces all the divisions with the function shown by @DamianCz. Yes, the NaN values are gone, but q will then just be [0, 0, 0] not the expected [14, 0, 0].

[donhatch]

I ran into this too. Another example:

input: [[0.018314685707290043, 0.1340867554784432],
        [0.13408675547842389,  0.98168531429271]]
output: {
  u: [[NaN,NaN],[NaN,NaN]],
  q: [0,NaN],
  v: [[0.9908003402768454,-0.1353317616352032],
      [-0.1353317616352032,-0.9908003402768454]]
}