The names of the routines are mnemonic and unique. Most routines are available in both a single precision and a double precision version, with names of the two versions sharing a common root. The root name is also the generic interface name. The name of the double precision specific version begins with a “D_” and the single precision specific version begins with an “S_”. For example, the following pairs are precision specific names of routines in the two different precisions: S_GQRUL/D_GQRUL (the root is “GQRUL ,” for “Gauss quadrature rule”) and S_RECCF/D_RECCF (the root is “RECCF,” for “recurrence coefficient”). The precision specific names of the IMSL routines that return or accept the type complex data begin with the letter “C_” or “Z_” for complex or double complex, respectively. Of course, the generic name can be used as an entry point for all precisions supported.

When this convention is not followed the generic and specific interfaces are noted in the documentation. For example, in the case of the BLAS and trigonometric intrinsic functions where standard names are already established, the standard names are used as the precision specific names. There may also be other interfaces supplied to the routine to provide for backwards compatibility with previous versions of the IMSL Fortran Numerical Library. These alternate interfaces are noted in the documentation when they are available.

Except when expressly stated otherwise, the names of the variables in the argument lists follow the Fortran default type for integer and floating point. In other words, a variable whose name begins with one of the letters “I” through “N” is of type INTEGER, and otherwise is of type REAL or DOUBLE PRECISION , depending on the precision of the routine.

An assumed-size array with more than one dimension that is used as a Fortran argument can have an assumed-size declarator for the last dimension only. In the MATH/LIBRARY routines, the information about the first dimension is passed by a variable with the prefix “LD” and with the array name as the root. For example, the argument LDA contains the leading dimension of array A. In most cases, information about the dimensions of arrays is obtained from the array through the use of Fortran 90’s size function. Therefore, arguments carrying this type of information are usually defined as optional arguments.

Where appropriate, the same variable name is used consistently throughout a chapter in the MATH/LIBRARY. For example, in the routines for random number generation, NR denotes the number of random numbers to be generated, and R or IR denotes the array that stores the numbers.

When writing programs accessing the MATH/LIBRARY, the user should choose Fortran names that do not conflict with names of IMSL subroutines, functions, or named common blocks. The careful user can avoid any conflicts with IMSL names if, in choosing names, the following rules are observed:

For further details, see the section on Reserved Names in the Reference Material.