Using ESSL 6.1 with multiple releases or PTFs

ESSL 6.1 supports the base release and multiple program temporary fixes (PTFs) coexisting on the same system, provided you install the base release and PTFs to an alternate directory and do not create symbolic links in the /usr directory.

In this case:

Specify the alternate directory, for example:
```
--prefix=/opt/ibmmathe6100
```
Set the IBM_ESSL_SYMBOLIC_LINK environment variable to no:
```
export IBM_ESSL_SYMBOLIC_LINK=no
```

This results in no symbolic links being created in the /usr directory, so you must identify the location of the ESSL libraries, header files, man pages and message catalog.

Fore example, if you install ESSL to the alternate directory /opt/ibmmathe6100, you must do the following to use ESSL:

Add -I/opt/ibmmathe6100/essl/6.1/include to your C/C++ compiler command.
Add -L/opt/ibmmathe6100/essl/6.1/lib64 -R/opt/ibmmathe6100/essl/6.1/lib64 to your link command.
Add /opt/ibmmathe6100/essl/6.1/man to your MANPATH environment variable.
Add /opt/ibmmathe6100/essl/6.1/msg/en_US to your NLSPATH environment variable.

As an alternative, if your compiler supports environment variables CPATH, LIBRARY_PATH and LD_LIBRARY_PATH, you can set these environment variables instead of changing your compile and link commands. For example:

export CPATH=/opt/ibmmathe6100/essl/6.1/include:${CPATH}
export LIBRARY_PATH=/opt/ibmmathe6100/essl/6.1/lib64:${LIBRARY_PATH}
export LD_LIBRARY_PATH=/opt/ibmmathe6100/essl/6.1/lib64:${LD_LIBRARY_PATH}