NASA Scientific and Technical Aerospace Reports

cost function. We also consider their performance in the context of an ICA algorithm based on non-orthogonal joint
diagonalization.
DTIC
Cost Estimates; Costs
20060001851 International Business Machines Corp., Yorktown Heights, NY USA
Recursive Array Layouts and Fast Matrix Multiplication
Chatterjee, Siddhartha; Lebeck, Alvin R.; Patnala, Praveen K.; Thottehodi, Mithuna; Jan. 1, 2005; 50 pp.; In English; Original
contains color illustrations
Contract(s)/Grant(s): DABT63-98-1-0001
Report No.(s): AD-A440384; No Copyright; Avail.: Defense Technical Information Center (DTIC)
The performance of both serial and parallel implementations of matrix multiplication is highly sensitive to memory
system behavior. False sharing and cache conflicts cause traditional column-major or row-major array layouts to incur high
variability in memory system performance as matrix size varies. This paper investigates the use of recursive array layouts to
improve performance and reduce variability. Previous work on recursive matrix multiplication is extended to examine several
recursive array layouts and three recursive algorithms: standard matrix multiplication, and the more complex algorithms of
Strassen and Winograd. While recursive layouts significantly outperform traditional layouts (reducing execution times by a
factor of 1.2-2.5) for the standard algorithm, they offer little improvement for Strassen’s and Winograd’s algorithms. For a
purely sequential implementation, it is possible to reorder computation to conserve memory space and improve performance
between 10% and 20%. Carrying the recursive layout down to the level of individual matrix elements is shown to be
counter-productive; a combination of recursive layouts down to canonically ordered matrix tiles instead yields higher
performance. Five recursive layouts with successively increasing complexity of address computation are evaluated, and it is
shown that addressing overheads can be kept in control even for the most computationally demanding of these layouts.
DTIC
Architecture (Computers); Computer Storage Devices; Layouts; Matrices (Mathematics); Multiplication; Recursive Functions
20060001879 Washington State Univ., Pullman, WA USA
Numerical Studies of Acoustic Propagation in Shallow Water
Schneider, John B.; Nov. 13, 2005; 7 pp.; In English
Contract(s)/Grant(s): N00014-96-1-0790
Report No.(s): AD-A440431; No Copyright; Avail.: CASI: A02, Hardcopy
Equations were derived which rigorously codify the propagation of fields in finite-difference time-domain (FDTD) grids.
These equations were then used to construct a perfect total-field/scattered field boundary (which is used to inject energy into
the grid). Algorithms were developed to enhance the modeling of material boundaries in the FDTD method; the accuracy of
various FDTD or FDTD-like algorithms were rigorously studied; an FDTD algorithm was developed which is theoretically
exact (i.e., provided the grid is infinite the accuracy is limited only by the finite precision of computers); various computer
programs related to the FDTD method were written; and information and programs were disseminated via journal
publications, conference presentations, and the Web.
DTIC
Acoustic Propagation; Acoustics; Differential Equations; Finite Difference Theory; Shallow Water
20060001928 Uniformed Services Univ. of the Health Sciences, Bethesda, MD USA
Chemical Vapor Identification Using Field-Based Attenuated Total Reflectance Fourier Transform Infrared Detection
and Solid Phase Microextraction
Bryant, Chet K.; Jun. 9, 2004; 111 pp.; In English; Original contains color illustrations
Report No.(s): AD-A440604; No Copyright; Avail.: Defense Technical Information Center (DTIC)
Attenuated total reflectance Fourier transform infrared (ATR-FTIR) technology is used to identify chemicals in a liquid
or solid phase but not in a vapor phase. This research identified vapor phase chemicals using a field-portable ATR-FTIR
spectrometer combined with a solid phase microextraction (SPME) film. Two nerve agent simulants, diisopropyl
methylphosphonate (DIMP) and dimethyl methylphosphonate (DMMP), and three polycarbosiloxane polymers were
evaluated using a TravelIR ATR-FTIR instrument. An SPME film was adhered to the TravelIR sampling interface to extract
and concentrate vapors to be identified by the TravelIR. The lowest air concentration identified was 50 ppb DIMP and 250
ppb DMMP. A remote sampling technique where SPME films were exposed to vapors and then transferred to the TravelIR
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