The matrices are obtained from Harwell-Boeing Sparse Matrix Collection from MatrixMarket, and are made symmetric (How?). Google search on each of these matrices (without the .sym sufix) should take you to its web page. The conversion from MatrixMarket format to PETSc binary is implemented by mm2petsc.c, mmio.c, and mmio.h mmio.c has a bugfix done by Victor Eijkhout, 2005. spd matrices: ============== S3DKQ4M2: ---------- Finite element analysis of cylindrical shells Cylindrical shell, uniform 150x100 quadrilateral mesh, R/t=1000 http://math.nist.gov/MatrixMarket/data/misc/cylshell/s3dkq4m2.html * Dimension N = 90449 * * Number of nonzero elements = 2455670 * S3DKT3M2: ----------- Finite element analysis of cylindrical shells Cylindrical shell, uniform 150x100 triangular mesh, R/t=1000 http://math.nist.gov/MatrixMarket/data/misc/cylshell/s3dkt3m2.html * Dimension N = 90449 * * Number of nonzero elements = 1921955 * indefinite: ============ 1138 BUS -------- Power systems admittance matrices Power system networks http://math.nist.gov/MatrixMarket/data/Harwell-Boeing/psadmit/1138_bus.html 1138x1138, 2596 entries, real symmetric indefinite symmetric positive definite BCSSTK26, BCSSTM26: --------------------- BCS Structural Engineering Matrices http://math.nist.gov/MatrixMarket/data/Harwell-Boeing/bcsstruc4/bcsstk26.html BCSSTK26: 1922 x 1922, 16129 entries real symmetric indefinite BCSSTM26: real symmetric positive definite, 1922 by 1922, 1922 entries both in sbaij format BCSSTK25, BCSSTM25: ------------------ BCSSTK25: 15439 x 15439, 133840 entries, real symmetric indefinite BCSSTM25: 15439 x 15439, 15439 entries, real symmetric positive definite both in sbaij format