Method decreaseKey

JSAT/src/jsat/utils/FibHeap.java:223–236

(FibNode<T> x, double k)

    }
    
    public void decreaseKey(FibNode<T> x, double k)
    {
        if(k > x.key)
            throw new RuntimeException("new key is greater than current key");
        x.key = k;
        FibNode<T> y = x.p;
        if(y != null && x.key < y.key)
        {
            cut(x, y);
            cascadingCut(y);
        }
        if(x.key < min.key)
            min = x;
    }
    
    /**
     *