(完整word版)四川大學(xué)系統(tǒng)級(jí)編程-2017-A卷答案.doc

1、2017F-SLP-A卷答案一每題 2 分，共 40 分BACBD ACAACDADAB CBDBB二 每題 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?jī)蓚€(gè)填空 1分）+-+|unknown|0xffff1004+-+|3|0xffff1000+-+|unknown|0xffff0ffc+-+|unknown|0xffff0ff8+-+|unknown|0xffff0ff4+-+|2|0xffff0ff0+-+

2、|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: 0xffff0f

3、d8（2 分）四共 12 分CodeminmaxincrsquareA1919090B9119090C119090This 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

4、+ *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 bewrong. 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

5、to conditions the programmer does not anticipate.五1. （5 分）答：如編譯執(zhí)行環(huán)境是逐行訪問(wèn)內(nèi)存，如C 語(yǔ)言，則此代碼有良好的空間局部性。如果如編譯執(zhí)行環(huán)境是逐列訪問(wèn)內(nèi)存,如matlab， 且 N 較大，則該代碼需跨行讀取數(shù)據(jù)，則此代碼空間局部性就較差。2. （10 分）A. 16*16*4B. 256, 每行一個(gè) cold missC. 25%, 每 4 個(gè)整數(shù)產(chǎn)生一個(gè) cold missD. 25%, cache 大小沒(méi)有什么影響六1. 【備注：非標(biāo)準(zhǔn)化考試】1 ） CSAPP ：中文： computer system: a programmers perspective英文：深入理解計(jì)算機(jī)系統(tǒng)2 ）可以（不限于）從下面的角度A ）整個(gè)計(jì)算機(jī)系統(tǒng)的核心部件：軟件（如編譯器和 OS ）和硬件（ CPU 、存儲(chǔ)系統(tǒng)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 tosome change in the processors state.（說(shuō)明：以上是教材/授課課件