Information on atlconf

NOTE: this information was out of date before it was finished, so this discussion should be viewed as an introduction only.

For ATLAS 3.7.12, ATLAS's configure routine was completely rewritten for greater modularity. The total amount of code probably increased, but the amount that must be examined at any time should be very much smaller.

In the new system, the topmost unit is ATLAS/configure which is a BFI shell script which allows ATLAS's config.c to be invoked in a way very similar to gnu configure. This shell script gathers some info and fills in a Makfile which is then used to build xconfig from ATLAS/CONFIG/src/config.c. config.c is a driver program that first calls various probes to determine any information not overridden by user flags, and then calls xspew to create a full Make.inc for the target architecture. xsprew is built from the file ATLAS/CONFIG/src/SpewMakeInc.c.

The idea is to change ATLAS's install so it consists of the following commands:

1. /path/to/ATLAS/configure : Create Make.inc and build subdirs in the present directory (ATLAS no longer requires building in arch-spec directories under the source tree)
2. make build : Build ATLAS
3. make check : run sanity tests
4. make time : run simple benchmarks, compare observed vs. expected performance, and issue warning if too low
   • Keep record of arch default installs with perfermance as % of clock rate (not peak!)
   • If arch def used wt bad compiler, this will detect performance difference, and user should be warned
   • If no arch defaults (so expected performance unknown), still create standard benchmark output file for submission to ATLAS
5. make install : copy libraries and include files to user-specified directories

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