Version 3 of the Hadley Centre Atmospheric Model (HadAM3) has been used to demonstrate one means of comparing a general circulation model with observations for a specific climate perturbation, namely the strong 1997/98 El Nino. This event was characterized by the collapse of the tropical Pacific's Walker circulation, caused by the lack of a zonal sea surface temperature gradient during the El Nino. Relative to normal years, cloud altitudes were lower in the western portion of the Pacific and higher in the eastern portion. HadAM3 likewise produced the observed collapse of the Walker circulation, and it did a reasonable job of reproducing the west/east cloud structure changes. This illustrates that the 1997/98 El Nino serves as a useful means of testing cloud-climate interactions in climate models.

Optimizing compilers have a long history of applying loop transformations to C and Fortran scientific applications. However, such optimizations are rare in compilers for object-oriented languages such as C++ or Java, where loops operating on user-defined types are left unoptimized due to their unknown semantics. Our goal is to reduce the performance penalty of using high-level object-oriented abstractions. We propose an approach that allows the explicit communication between programmers and compilers. We have extended the traditional Fortran loop optimizations with an open interface. Through this interface, we have developed techniques to automatically recognize and optimize user-defined array abstractions. In addition, we have developed an adapted constant-propagation algorithm to automatically propagate properties of abstractions. We have implemented these techniques in a C++ source-to-source translator and have applied them to optimize several kernels written using an array-class library. Our experimental results show that using our approach, applications using high-level abstractions can achieve comparable, and in cases superior, performance to that achieved by efficient low-level hand-written codes.

It is well established that bitmap indices are efficient for read-only attributes with a small number of distinct values. For an attribute with a large number of distinct values, the size of the bitmap index can be very large. To over come this size problem, specialized compression schemes are used. Even though there is empirical evidence that some of these compression schemes work well, there has not been any systematic analysis of their effectiveness. In this paper, we analyze the time and space complexities of the two most efficient bitmap compression techniques known, the Byte-aligned Bitmap Code (BBC) and the Word-Aligned Hybrid (WAH) code, and study their performance on high cardinality attributes. Our analyses indicate that both compression schemes are optimal in time. The time and space required to operate on two compressed bitmaps are proportional to the total size of the two bitmaps. We demonstrate further that an in-place OR algorithm can operate on a large number of sparse bitmaps in time linear in their total size. Our analyses also show that the compressed indices are relatively small compared with commonly used indices such as B-trees. Given these facts, we conclude that bitmap index is efficient on attributes of …

A Family of Durable Silver Mirror Designs has been fabricated at LLNL. We report here on the optical and environmental performance of the basic design, which can be cleaned with standard glass cleaner and cloth after months of exposure to outside atmosphere.