The vandermonde matrix is not invertible?

[lpstudy]

Intel ISA-L told that using this way to construct Vandermonde matrix does not guarantee the invertible property for the sub matrix. I hope to get help from you.

Do I make a mistake or in your condition, this works well engough?

[drmingdrmer]

Yes Vandermonde matrix does not guarantee invertable for sub matrix.
Use the Cauchy matrix instead.

Do I make a mistake or in your condition, this works well engough?

I do not get what you mean about the "mistake".
Here I have a short explain about the invertibility which might help you a bit: http://drmingdrmer.github.io/tech/distributed/2017/02/01/ec.html#vandermonde-%E7%9F%A9%E9%98%B5%E7%9A%84%E5%8F%AF%E9%80%86%E6%80%A7