Which embeddable DBMS to use for linear algebra library?

Question

Java

Requirements: RAM up to 4 - 8 GB, it is impossible to put the whole matrix/vector into double[] .

At the moment, the existing solution in the form of using MappedByteBuffer stumbled upon the performance problem of sequential access to vector or matrix data. I guess it's a bicycle compared to RDBMS.

0. Should I use an embedded DBMS? If not, how would you solve this problem?

1. What embedded DBMS should be used for the linear algebra library, taking into account the requirements for maximum performance (read / write) with large dimensions (for example, a matrix of 1_000_000 by 1_000_000)?

Thanks for the replies.