UNIX/IRAF Site Manager's Guide

UNIX/IRAF Site Manager's Guide

3.1. Multiple architecture support

Often the computing facilities at a site consist of a heterogeneous network of workstations and servers. These machines will often have quite different architectures. Considering only a single vendor like Sun, as of 1992 one sees the three major architectures SPARC, Motorola 68020, and Intel 80386, and several minor variations on these architectures, i.e., the floating point options for the Sun-3, namely the Motorola 68881 coprocessor, the Sun floating point accelerator (FPA), and software floating point (Sun is trying to phase some of these out but the need for multiple architecture support is not likely to go away). On the Decstation we currently support two architectures, one (ddec) using the DEC Fortran compiler, and the other (dmip) using the MIPS Risc Fortran compiler. Other systems such as SGI/IRAF or the VAXstation support only a single architecture.

Since IRAF is a large system it is undesirable to have to maintain a separate copy of IRAF for each machine architecture on a network. For this reason IRAF provides support for multiple architectures within a single copy of IRAF. To be accessible by multiple network clients, this central IRAF system will typically be NFS mounted on each client.

Multiple architecture support is implemented by separating the IRAF sources and binaries into different directory trees. The sources are architecture independent and hence sharable by machines of any architecture. All of the architecture dependence is concentrated into the binaries, which are collected together into the so-called BIN directories, one for each architecture. The BIN directory contains all the object files, object libraries, executables, and shared library images for an architecture, supporting both IRAF execution and software development for that architecture. A given system can support any number of BIN directories, and therefore any number of architectures.

In IRAF terminology, when we refer to an "architecture" what we really mean is a type of BIN. The correspondence between BINs and hardware architectures is not necessarily one-to-one, i.e., multiple BINs can exist for a single compiler architecture by compiling the system with different compilation flags, as different versions of the software, and so on. Examples of some currently supported software architectures are shown below.

Architecture	System	    Description

generic any no binaries (default IRAF configuration) sparc Sun-4 Sun SPARC (RISC) architecture, integral fpu f68881 Sun-3 mc68020, 68881 floating point coprocessor pg Sun-4 Sun/IRAF compiled for profiling ddec Decstation DEC Fortran version of DSUX/IRAF dmip Decstation MIPS Risc Fortran version of DSUX/IRAF rs6000 IBM IBM RS/6000 running AIX irix SGI SGI IRIX, MIPS cpu f2c Macintosh A/UX, using Fortran-to-C translation and GCC

Most of these correspond to hardware architectures or floating point hardware options. The exceptions are the generic architecture, which is what the distributed system is configured to by default (to avoid having any architecture dependent binary files mingled with the sources), and the "pg" architecture, which is not normally distributed to user sites, but is a good example of a custom software architecture used for software development.

When running IRAF on a system configured for multiple architectures, selection of the BIN (architecture) to be used is controlled by the UNIX environment variable IRAFARCH, e.g.,

% setenv IRAFARCH ddec
would cause IRAF to run using the ddec architecture, corresponding to the BIN directory bin.ddec. Once inside the CL one can check the current architecture by entering one of the following commands (the output in each case is shown as well).
cl> show IRAFARCH
ddec
or
cl> show arch
.ddec
If IRAFARCH is undefined at CL startup time a default architecture will be selected based on the current machine architecture, the available floating point hardware, and the available BINs. The IRAFARCH variable controls not only the architecture of the executables used to run IRAF, but the libraries used to link IRAF programs, when doing software development from within the IRAF or host environment.
Additional information on multiple architecture support is provided in the system notes file for V2.8, file doc$notes.v28.