ON THE ACCELERATION OF SHORTEST PATH CALCULATIONS IN TRANSPORTATION NETWORKS
Abstract
Shortest path algorithms are a key element of many graph problems. They are used in such applications as online direction finding and navigation, as well as modeling of traffic for large scale simulations of major metropolitan areas. As the shortest path algorithms are an execution bottleneck, it is beneficial to move their execution to parallel hardware such as FieldProgrammable Gate Arrays (FPGAs). Hardware implementation is accomplished through the use of a small A core replicated on the order of 20 times on an FPGA device. The objective is to maximize the use of onboard randomaccess memory bandwidth through the use of multithreaded latency tolerance. Each shortest path core is responsible for one shortest path calculation, and when it is finished it outputs its result and requests the next source from a queue. One of the innovations of this approach is the use of a small bubble sort core to produce the extractmin function. While bubble sort is not usually considered an appropriate algorithm for any nontrivial usage, it is appropriate in this case as it can produce a single minimum out of the list in O(n) cycles, whwere n is the number of elements in the vertext list. The costmore »
 Authors:
 Los Alamos National Laboratory
 Publication Date:
 Research Org.:
 Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
 OSTI Identifier:
 1000496
 Report Number(s):
 LAUR070085
TRN: US201101%%364
 DOE Contract Number:
 AC5206NA25396
 Resource Type:
 Conference
 Resource Relation:
 Conference: IEEE SYMPOSIUM ON FIELDPROGRAMMABLE CUSTON COMPUTING MACH ; 200704 ; NAPA
 Country of Publication:
 United States
 Language:
 English
 Subject:
 99; ACCELERATION; ALGORITHMS; ARCHITECTURE; BUBBLES; IMPLEMENTATION; MEMORY MANAGEMENT; NAVIGATION; QUEUES; SIMULATION; TOLERANCE; URBAN AREAS
Citation Formats
BAKER, ZACHARY K., and GOKHALE, MAYA B.. ON THE ACCELERATION OF SHORTEST PATH CALCULATIONS IN TRANSPORTATION NETWORKS. United States: N. p., 2007.
Web.
BAKER, ZACHARY K., & GOKHALE, MAYA B.. ON THE ACCELERATION OF SHORTEST PATH CALCULATIONS IN TRANSPORTATION NETWORKS. United States.
BAKER, ZACHARY K., and GOKHALE, MAYA B.. Mon .
"ON THE ACCELERATION OF SHORTEST PATH CALCULATIONS IN TRANSPORTATION NETWORKS". United States.
doi:. https://www.osti.gov/servlets/purl/1000496.
@article{osti_1000496,
title = {ON THE ACCELERATION OF SHORTEST PATH CALCULATIONS IN TRANSPORTATION NETWORKS},
author = {BAKER, ZACHARY K. and GOKHALE, MAYA B.},
abstractNote = {Shortest path algorithms are a key element of many graph problems. They are used in such applications as online direction finding and navigation, as well as modeling of traffic for large scale simulations of major metropolitan areas. As the shortest path algorithms are an execution bottleneck, it is beneficial to move their execution to parallel hardware such as FieldProgrammable Gate Arrays (FPGAs). Hardware implementation is accomplished through the use of a small A core replicated on the order of 20 times on an FPGA device. The objective is to maximize the use of onboard randomaccess memory bandwidth through the use of multithreaded latency tolerance. Each shortest path core is responsible for one shortest path calculation, and when it is finished it outputs its result and requests the next source from a queue. One of the innovations of this approach is the use of a small bubble sort core to produce the extractmin function. While bubble sort is not usually considered an appropriate algorithm for any nontrivial usage, it is appropriate in this case as it can produce a single minimum out of the list in O(n) cycles, whwere n is the number of elements in the vertext list. The cost of this min operation does not impact the running time of the architecture, because the queue depth for fetching the next set of edges from memory is roughly equivalent to the number of cores in the system. Additionally, this work provides a collection of simulation results that model the behavior of the node queue in hardware. The results show that a hardware queue, implementing a small bubbletype minimum function, need only be on the order of 16 elements to provide both correct and optimal paths. Because the graph database size is measured in the hundreds of megabytes, the Cray SRAM memory is insufficient. In addition to the A* cores, they have developed a memory management system allowing roundrobin servicing of the nodes as well as virtual memory managed over the Hypertransport bus. With support for a DRAM graph store with SRAMbased caching on the FPGA, the system provides a speedup of roughly 8.9x over the CPUbased implementation.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Mon Jan 08 00:00:00 EST 2007},
month = {Mon Jan 08 00:00:00 EST 2007}
}

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