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###

Testing IEEE arithmetic and ILAENV

As some new routines in LAPACK rely on IEEE-754 compliance,
two settings (`ISPEC=10` and `ISPEC=11`) have been added to ILAENV
(`LAPACK/SRC/ilaenv.f`) to denote IEEE-754 compliance for NaN and
infinity arithmetic, respectively. By default, ILAENV assumes an IEEE
machine, and does a test for IEEE-754 compliance. **NOTE: If you
are installing LAPACK on a non-IEEE machine, you MUST modify ILAENV,
as this test inside ILAENV will crash!**

If `ILAENV( 10, )` or `ILAENV( 11, )` is
issued, then `ILAENV=1` is returned to signal IEEE-754 compliance,
and `ILAENV=0` if the architecture is non-IEEE-754 compliant.

Thus, for non-IEEE machines, the user must hard-code the setting of
(`ILAENV=0`) for (`ISPEC=10` and `ISPEC=11`) in the version
of `LAPACK/SRC/ilaenv.f` to be put in
his library. There are also specialized testing and timing^{2}versions of
ILAENV that will also need to be modified.

- Testing/timing version of
`LAPACK/TESTING/LIN/ilaenv.f`
- Testing/timing version of
`LAPACK/TESTING/EIG/ilaenv.f`
- Testing/timing version of
`LAPACK/TIMING/LIN/ilaenv.f`
- Testing/timing version of
`LAPACK/TIMING/EIG/ilaenv.f`

The test program in `LAPACK/INSTALL/tstiee.f` checks an installation
architecture
to see if infinity arithmetic and NaN arithmetic are IEEE-754 compliant.
A warning message to the user is printed if non-compliance is detected.
This same test is performed inside the function ILAENV. If
`ILAENV( 10, )` or `ILAENV( 11, )` is
issued, then `ILAENV=1` is returned to signal IEEE-754 compliance,
and `ILAENV=0` if the architecture is non-IEEE-754 compliant.

To avoid this IEEE test being run every time you call
`ILAENV( 10, )` or `ILAENV( 11, )`, we suggest
that the user hard-code the setting of
`ILAENV=1` or `ILAENV=0` in the version of `LAPACK/SRC/ilaenv.f` to be put in
his library. As aforementioned, there are also specialized testing and
timing^{2}versions of ILAENV that will also need to be modified.

** Next:** Create the BLAS Library
** Up:** Test and Install the
** Previous:** Installing SECOND and DSECND
** Contents**
Julie Langou
2007-02-26