I am currently working on writing a UMAT subroutine. In one part of the code, I need to solve a system of linear equations. Initially, I used Fortran libraries such as LAPACK and PARDISO for solving the system, but they were unable to provide accurate solutions for the equation’s roots when the matrixes are very large and sparse. In contrast, MATLAB can calculate these roots with high accuracy. To address this, I established a connection between Fortran and MATLAB to compute the roots directly within the Fortran code.