The name of each LAPACK routine is a coded specification of its function (within the very tight limits of standard Fortran 77 6-character names).
All driver and computational routines have names of the form XYYZZZ, where for some driver routines the 6th character is blank.
The first letter, X, indicates the data type as follows:
S REAL D DOUBLE PRECISION C COMPLEX Z COMPLEX*16 or DOUBLE COMPLEX
When we wish to refer to an LAPACK routine generically, regardless of data type, we replace the first letter by ``x''. Thus xGESV refers to any or all of the routines SGESV, CGESV, DGESV and ZGESV.
The next two letters, YY, indicate the type of matrix (or of the most significant matrix). Most of these two-letter codes apply to both real and complex matrices; a few apply specifically to one or the other, as indicated in Table 2.1.
BD bidiagonal GB general band GE general (i.e., unsymmetric, in some cases rectangular) GG general matrices, generalized problem (i.e., a pair of general matrices) (not used in Release 1.0) GT general tridiagonal HB (complex) Hermitian band HE (complex) Hermitian HG upper Hessenberg matrix, generalized problem (i.e a Hessenberg and a triangular matrix) (not used in Release 1.0) HP (complex) Hermitian, packed storage HS upper Hessenberg OP (real) orthogonal, packed storage OR (real) orthogonal PB symmetric or Hermitian positive definite band PO symmetric or Hermitian positive definite PP symmetric or Hermitian positive definite, packed storage PT symmetric or Hermitian positive definite tridiagonal SB (real) symmetric band SP symmetric, packed storage ST (real) symmetric tridiagonal SY symmetric TB triangular band TG triangular matrices, generalized problem (i.e., a pair of triangular matrices) (not used in Release 1.0) TP triangular, packed storage TR triangular (or in some cases quasi-triangular) TZ trapezoidal UN (complex) unitary UP (complex) unitary, packed storage
When we wish to refer to a class of routines that performs the same function on different types of matrices, we replace the first three letters by ``xyy''. Thus xyySVX refers to all the expert driver routines for systems of linear equations that are listed in Table 2.2.
The last three letters ZZZ indicate the computation performed. Their meanings will be explained in Section 2.3. For example, SGEBRD is a single precision routine that performs a bidiagonal reduction (BRD) of a real general matrix.
The names of auxiliary routines follow a similar scheme except that the 2nd and 3rd characters YY are usually LA (for example, SLASCL or CLARFG). There are two kinds of exception. Auxiliary routines that implement an unblocked version of a block algorithm have similar names to the routines that perform the block algorithm, with the sixth character being ``2'' (for example, SGETF2 is the unblocked version of SGETRF). A few routines that may be regarded as extensions to the BLAS are named according to the BLAS naming schemes (for example, CROT, CSYR).