四川大学系统级编程-2017-A卷答案.doc

2017F-SLP-A卷答案一每题2分，共40分BACBD ACAACDADAB CBDBB2 每题5分，共10分int NegativeNum (int x) return (x) & (0x80000000);int SetByte (int x,int n) return x|(0xFF (n3);三共13分9分（每两个填空1分） +-+ | unknown | 0xffff1004 +-+ | 3 | 0xffff1000 +-+ | unknown | 0xffff0ffc +-+ | unknown | 0xffff0ff8 +-+ | unknown | 0xffff0ff4 +-+ | 2 | 0xffff0ff0 +-+ | 0x08048407 | 0xffff0fec +-+ | 0xffff0ff8 | 0xffff0fe8 +-+ | unknown | 0xffff0fe4 +-+ | 1 | 0xffff0fe0 +-+ | 0x08048432 | 0xffff0fdc +-+ | 0xffff0fe8 | 0xffff0fd8 +-+ | unknown | 0xffff0fd4 +-+ | 0 | 0xffff0fd0 +-+ | 0x08048407 | 0xffff0fcc +-+ | 0xffff0fd8 | 0xffff0fc8 +-+ | 0 | 0xffff0fc4 +-+ | unknown | 0xffff0fc0 +-+ esp: 0xffff0fcc （2分）ebp: 0xffff0fd8 （2分）四共12分Code minmax incr square A1919090B9119090C119090This problem illustrates some of the subtle effects of memory aliasing, and it cannot be used to swap two values (2 scores). As the commented code below shows, the effects will be to set the value at xp to zero when xp equals to xy. 1 *xp = *xp + *xp; / 2x2 *xp = *xp - *xp; / 2x 2x = 03 *xp = *xp - *xp; / 0 0 = 0 (4 scores)This example illustrates that our intuition about program behavior can often be wrong. We naturally think of the case where xp and yp are distinct but overlook the possibility that they might be equal. Bugs often arise due to conditions the programmer does not anticipate. 五1. （5分）答：如编译执行环境是逐行访问内存，如C语言，则此代码有良好的空间局部性。如果如编译执行环境是逐列访问内存,如matlab， 且N较大，则该代码需跨行读取数据，则此代码 空间局部性就较差。2. （10分）A. 16*16*4 B. 256, 每行一个cold missC. 25%, 每4个整数产生一个cold missD. 25%, cache 大小没有什么影响六1. 【备注：非标准化考试】1） CSAPP：中文：computer system: a programmers perspective英文：深入理解计算机系统2） 可以（不限于）从下面的角度A） 整个计算机系统的核心部件：软件（如编译器和OS）和硬件（CPU、存储系统登）B） 程序的生命周期2.1） 概念：An exception is an abrupt change in the control flow in response to some change in the processors state.（说