Yoshimori Nakase

An elementary processor architecture with simultaneous instruction issuing from multiple threads

In this paper, we propose a multithreaded processor architecture which improves machine throughput. In our processor architecture, instructions from different threads (not a single thread) are issued simultaneously to multiple functional units, and these instructions can begin execution unless there are functional unit conflicts. This parallel execution scheme greatly improves the utilization of the functional unit. Simulation results show that by executing two and four threads in parallel on a nine-functional-unit processor, a 2.02 and a 3.72 times speed-up, respectively, can be achieved over a conventional RISC processor. Our architecture is also applicable to the efficient execution of a single loop. In order to control functional unit conflicts between loop iterations, we have developed a new static code scheduling technique. Another loop execution scheme, by using the multiple control flow mechanism of our architecture, makes it possible to parallelize loops which are difficult to parallelize in vector or VLIW machines.

A new color conversion method for realistic light simulation

In this paper a new color conversion method to replace the RGB approximation based on the perceived change in color when a colored light source illuminates a surface is proposed. In our study 1200 uniformly distributed samples were taken from Commission Internationale de l’Eclairage 1976 L*a*b* uniform color space and used to construct a uniform subset. Photographic patches of the colors in this subset were then subjected to color light sources and the color changes were measured. From these measurements rules which govern the corresponding change within the color space were determined. Changes within the color space were then defined by simple linear equations for any light source illuminating any surface. Lastly, experiments were conducted to confirm that color conversion within the CIE color space generates more realistic images than RGB approximations for a variety of light sources.