The solution of the 15,112-city traveling salesman problem was accomplished in several phases in 2000/2001. The initial tour-finding and cutting-plane phases were run on a cluster of Compaq ES40 Alphaservers consisting of 32 EV6 (500 MHz) nodes and 12 EV67 (667 MHz) nodes. The cluster is located at Rice University; it is the primary computing facility for the Compaq-Rice High Performance Computing Initiative. The final branching phase of the computation was run on the ES40 cluster, plus a network of Compaq DS20 servers and XP10000 workstations at Rice, a cluster of AMD-based FreeBSD workstations at Rice, and a network of Intel-based Linux workstations in the Applied and Computational Mathematics program at Princeton University.

Available CPU summary

System Model	CPU type	# CPUs available	Spec CPU95 Int/FP
Compaq XP1000	500 MHz Alpha 21264	5	26.9/52.2
Compaq DS20	500 MHz Alpha 21264	6	27.7/58.7
Compaq ES40	500 MHz Alpha 21264-6	32	27.3/57.7
Compaq ES40	667 MHz Alpha 21264-67	12	40.0/82.7
AMD FreeBSD Workstation	800 MHz Athalon	24	34.9/26.7
Intel Linux Workstation	Mix of 450 to 1,000 MHz Pentium III	19	-
Digital AS4100 5/400	400 MHz Alpha 21164	12	12.1/17.2

The computations used a total of 22.6 years of computer time, adjusted to a 500 MHz, EV6 Alpha processor.