Stabilization techniques for spectral methods

We introduce a stabilized treatment of spectral methods. The condition number of the spectral systems is highly improved. Elliptic and biharmonic problems are considered. Suitable interpolants in the case of inhomogeneous Dirichlet boundary conditions are presented. For a direct solver the improvements with respect to rounding error propagation are numerically demonstrated.     

On calibration error of randomized forecasting algorithms

It has been recently shown that calibration with an error less than Δ>0$\Delta >0$ is almost surely guaranteed with a randomized forecasting algorithm, where forecasts are obtained by random rounding the deterministic forecasts up to Δ$\Delta$. We show that this error cannot be improved for a vast majority of sequences: we prove that, using a probabilistic algorithm, we can effectively generate with probability close to one a sequence “resistant” to any randomized rounding forecasting with an error much smaller than Δ$\Delta$. We also reformulate this result by means of a probabilistic game.     

通用扫描线多边形填充算法

传统的扫描线多边形填充算法只适用于水平扫描线的逐行填充。文章提出通用扫描线多边形填充算法,该算法可以有效地解决任意间距、任意倾角的扫描线对多边形的填充问题。通用扫描线多边形算法采用了坐标变换、浮点数舍入策略等重要方法。顶点扫描线号是该算法中的核心概念。     

求补舍入并行和位长自适应整数转浮点数电路设计

提出了一种实现整数转浮点数的新的设计方法 ,并且对方法的正确性给予了证明 .采用这种设计方法 ,实现了求补和舍入的合并并行 ,使关键路径的延时比常规的电路设计方案减少了 15级门 ,同时降低了电路规模 .关键路径延时的减小 ,使这一转换可以在单周期内完成 .另外 ,该方法实现了位长自适应 ,只需花费很少的电路规模和延时实现控制 ,就可以适应长整型、整型到单、双精度浮点数的转换 ,增强了电路功能 .这一设计方法同样适用于其逆转换 .该转换模块采用 Fujitsu CE71库设计 ,在 10 0 MHz主频下经仿真验证 ,结果正确 ,已经应用到实际工程中 .     

位数随机的有效数字自动运算算法

针对物理实验数据的自动处理,提出一种位数随机的有效数字自动运算算法,包括有效数字运算结果的科学记数表示算法、有效位数的取舍算法、数据表示形武的转换算法以及不同位数有效数字的运算算法.对有效数字多项式的自动运算实验结果表明,该算法符合运算优先级的要求,运算结果符合有效数字的取舍原则,算法运算的结果与人工运算的结果完全相同,算法满足位数随机的物理实验数据的自动处理要求.     

无网格线探索布线算法

提出的一种高效快速的无网格线探索面线算法适用于焊盘外形尺寸不一，线宽及线间距离可变的印制电路板及ＭＣＭ电路布线，精心设计的数据结构及灵活的绕障探索方式可大大地提高搜索效率；多级多扁优化策略为改善布线结果提供了可靠的保证，该算法已成功地应用于通用印制电路板设计系统ＭＰＣＢ，取得了令人满意的效果。     

三相变压器励磁涌流及保护方案

针对近期基于波形对称原理的变压器差动保护频繁误动的现状,从三相变压器励磁涌流的产生机理入手,分析了波形对称原理与2次谐波制动原理的内在联系,结合目前流行的2种相位补偿方式,指出了传统采用相间差动的保护方案误动的根本原因.针对220 kV以上D侧套管内装设电流互感器的变压器,提出了一种采用相电流差动接线的保护方案.该方案在理论上克服了传统方案的全部弊端,并可实现真正的分相制动;缺点在于保护范围有所减小,需要其他保护来配合.     

压头钝化对纳米硬度测量的影响

压头面积函数是影响纳米硬度测量的一个主要因素。本文对由于压头端部钝化对纳米硬度测量的影响进行了分析,并通过实验进行了验证。结果表明,面积函数校准对提高纳米硬度等材料力学性能参数的测量准确性十分必要。     

Perturbing and evaluating numerical programs without recompilation—the wonglediff way

wonglediff is a program that tests the sensitivity of arbitrary program executables or processes to changes that are introduced by a process that runs in parallel. On Unix and Linux kernels, wonglediff creates a supervisor process that runs applications and, on the fly, introduces desired changes to their process state. When execution terminates, it then summarizes the resulting changes in the output files. The technique employed has a variety of uses. This paper describes an implementation of wonglediff that checks the sensitivity of programs to random changes in the floating‐point rounding modes. It runs a program several times, ‘wongling’ it each time: randomly toggling the IEEE‐754 rounding mode of the program as it executes. By comparing the resulting output, one gets a poor man's numerical stability analysis for the program. Although the analysis does not give any kind of guarantee about a program's stability, it can reveal genuine instability, and it does serve as a particularly useful and revealing idiot light. In our implementation, differences among the output files from the program's multiple runs are summarized in a report. This report is in fact an HTML version of the output file, with inline mark‐up summarizing individual differences among the multiple instances. When viewed with a browser, the differences can be highlighted or rendered in many different ways. Copyright © 2004 John Wiley & Sons, Ltd.     

一种可配置的桶式移位器的设计

根据CPU的中指令的不同，实现了一种可配置的桶式移位器，可以将将移器配置为通用移位器或对位移位移位器，采用这种桶式移位器，可以使采用部分译码方式的移位器在原有功能的基础上增加对位右移的功能，并同时产生满足IEEE舍入要求的附加位，在增加少量控制逻辑的基础上，使浮点运算的对位移位器与定点运算实现移位操作的通用顺合二为一，增强了桶式移位器的可复用性，减少了CPU芯片的面积，不需增加关键路径的长度，电路布线规整，易于VLSI实现。