On entry: the first dimension of the array q as declared in the (sub)program from which f08qtf is called.
if , ;
if , .
7: – IntegerInput
8: – IntegerInput
On entry: ifst and ilst must specify the reordering of the diagonal elements of . The element with row index ifst is moved to row ilst by a sequence of exchanges between adjacent elements.
9: – IntegerOutput
On exit: unless the routine detects an error (see Section 6).
6Error Indicators and Warnings
If , argument had an illegal value. An explanatory message is output, and execution of the program is terminated.
The computed matrix is exactly similar to a matrix , where
and is the machine precision.
The values of the eigenvalues are never changed by the reordering.
8Parallelism and Performance
Background information to multithreading can be found in the Multithreading documentation.
f08qtf makes calls to BLAS and/or LAPACK routines, which may be threaded within the vendor library used by this implementation. Consult the documentation for the vendor library for further information.
Please consult the X06 Chapter Introduction for information on how to control and interrogate the OpenMP environment used within this routine. Please also consult the Users' Note for your implementation for any additional implementation-specific information.
The total number of real floating-point operations is approximately if , and if , where .