EISPACK is asoftware library fornumerical computation ofeigenvalues andeigenvectors of matrices, written inFORTRAN. It contains subroutines for calculating the eigenvalues of nine classes ofmatrices: complex general, complexHermitian, real general, real symmetric, real symmetricbanded, real symmetric tridiagonal, special real tridiagonal, generalized real, and generalized real symmetric matrices.In addition, it includes subroutines to perform asingular value decomposition.

Originally written around 1972–1973,^[1] EISPACK, likeLINPACK andMINPACK, originated fromArgonne National Laboratory, has always been free, and aims to beportable, robust and reliable. The library drew heavily on algorithms developed byJames Wilkinson, which were originally implemented inALGOL. Brian Smith led a team at Argonne developing EISPACK, initially by translating these algorithms into FORTRAN.Jack Dongarra joined the team as an undergraduate intern at Argonne, and later went on to createLAPACK, which has largely superseded EISPACK and LINPACK.

• Smith, Brian; Boyle, James;Dongarra, Jack; Garbow, Burton; Ikebe, Y; Klema, V;Moler, Cleve (1976).Matrix Eigensystem Routines - EISPACK Guide.Lecture Notes in Computer Science 6. Springer.ISBN 978-3-540-07546-2.
• Garbow, Burton; Boyle, James;Dongarra, Jack;Moler, Cleve (1977).Matrix Eigensystem Routines - EISPACK Guide Extension.Lecture Notes in Computer Science 51. Springer.ISBN 978-3-540-08254-5.

• Netlibdownload site for EISPACK
• Interview withJack Dongarra about EISPACK.

• Fortran libraries
• Numerical linear algebra
• Numerical software