Guys I was reading about CG method to solve the sparse systems. I came across that the method is defined for positive definite symmetric matrices. I was wondering does it converges for negative definite matrices too ?
$Ax =b \iff (-A) x = -b$, and if $A$ is symmetric negative definite then $-A$ is symmetric positive definite. So you can use CG to solve $-Ax = -b$.