just joined this forum as i got into a problem while using LAPACK routine (DSYGV). i am using fortran 95 for an eigen value analysis for type Ax=lamda B type problem. i am trying to get the eigen value using the routine, and it gives first two eigen values as -ve which is not expected. i ran previously on 5 similar models and i got the eigen values as expected.. what could be reason for this negative value in eigen value listing. I checked both matrices - A and B, they are square, symmetric and all the diagonal elements are positive elements in all 6 cases. i could upload the matrices if anyone wish to see them - they are 660 X660 matrices - around 11mb each in csv format. appreciate any guidance here.