Constraint Satisfaction with Preferences
PhD Thesis Summary
Hana Rudová
Faculty of Informatics,Masaryk University
Brno,Czech Republic
http://www.fi.muni.cz/~hanka
January2001
First works on constraint satisfaction problems(CSP)can be traced in the70’th but their widespread study and application started since the end of80’th when the extension of uni?-cation algorithm of logic programming led to the proposal of constraint logic programming (CLP)scheme.Introductory part of the thesis introduces both proposals as approaches allowing to express properties of the problem declaratively by means of constraints and to search for its solution via specialized algorithms.Presented thesis is focused on CSPs on?nite domains because of their practical applicability.Generally95%of all industrial constraint-based applications are formulated as CSPs on?nite domains.Constraint program-ming is applied to solve wide range of problems,among them scheduling,con?guration, hardware veri?cation,graphical interfaces,or molecular biology.However,in most real-life situations we need to express fuzziness,possibilities,probabilities,costs,...While problems may become over-constrained it does not make sense to say there is no solution.Many prob-lems require?nding of best or optimal solution wrt.one or even more optimization criteria. Others may be ill-de?ned and we need to include uncertainty of the problem de?nition into ?nal solution.All these problems need to apply some type of preferences which have to be in-cluded into both declarative and control part of the solution.That led us to the study of CSPs with preferences from both theoretical(proposal of new methodologies and uniform view to the existing ones)and practical(their application in timetabling area)points of view within this thesis.
1Frameworks
After short introduction of CSP&CLP schemes,we may proceed through description of particular frameworks for solving CSPs with preferences.As we intended to give a unifying view to particular approaches,we have proposed a uniform structure which is followed by all frameworks.Each of them elucidates notions of constraint(natural extension of constraint de?nition by a speci?c preference),problem(how it is extended to handle given preferences), distribution(a function aimed to evaluate particular assignments based on preferences),so-lution(de?ned with help of distribution via its optimal value),and consistency(up to which extent may be given problem satis?ed).
Starting from the basic frameworks over particular types of preferences(weighted,proba-bilistic,possibilistic,fuzzy CSPs)we continue through meta-frameworks(partial,valued,semiring-based CSPs).Basic frameworks may be obtained by speci?cation of a general algebraic struc-ture of meta-frameworks.Weighted CSP applies costs to optimize satisfaction of particular constraints(e.g.,minimize sum of weights of unsatis?ed constraints).Probabilities allow to express the degrees how much each constraint is valid in some ill-de?ned problem.Here we need to search for a de?nition of the real problem together with its best solution.Possibilistic CSP assigns a possibility degree to each constraint expressing how desirable its satisfaction is.This problem together with fuzzy CSP may be handled via min-max optimization.Fuzzy CSP associates the same type of preference to each tuple of values of constraint,however.
Partial CSP introduces the?rst attempt towards the generalization of basic approaches via problem https://www.doczj.com/doc/8a2964873.html,ter proposed valued CSP(VCSP)and semiring-based CSP(SCSP) build axiomatic theories which enable the construction of non trivial generic properties and algorithms.Particular formalisms de?ne monoid and lattice structures to catch particular preferences.While the monoid structure is able to handle only totally ordered preferences, SCSP with its lattice structure may represent partial ordering also.Multi-criteria optimization belongs to a typical representatives which require this property.
Even if SCSP is able to handle partial ordering of preferences,relation of equivalence between different SCSPs is not able to consider them.This led us to de?nition of a new equivalence and re?nement which are able to compare SCSP classes with partial ordering of preferences too.This de?nition remains in accordance with basic idea behind the re?ne-ment:if some problem is a re?nement of another one,then its set of solutions is included in the set of the later problem.
Together with the comparison of meta-frameworks,?nal part of this chapter summarizes relationships between particular basic frameworks which may be partitioned according to the idempotency of uni?able operator of both algebraic structures.Classical CSP,possibilistic and fuzzy CSP may be transformed via polynomial re?nement into weighted CSP but the opposite transformation doesn’t exist.It means that problem of?nding optimal solution of weighted CSP can not be reduced to fuzzy CSP.
2Constraint Hierarchies
Constraint hierarchies(CHs)and namely hierarchical constraint logic programming belong to traditional frameworks for handling of over-constrained problems.They allow to express hard constraints which has to be satis?ed and several preference levels of soft constraints which violations are minimized level by level subsequently.CHs de?ne the so called comparators aimed to select solutions(the best assignment of values to particular variables)via minimiz-ing errors of violated constraints.Global comparators aggregate errors of violated constraints at each level,basically we may compare weighted sum of errors or error of worst satis?ed constraint(weighted-sum-better and worst-case-better comparators).Local(locally-better)com-parator considers each constraint individually,regional comparator is able to select among assignments by individual comparison of constraints at some lower level even if they are incomparable at higher levels.
We have enhanced classical local comparator such that it is able to apply weights similar to those existing for weighted-sum-better comparator and proposed the so called ordered-better comparator[1].We have studied its relationship with locally-better comparator—
based on it and on existing algorithm for locally-better comparator we have proposed a new extended algorithm which is able to?nd ordered-better solution of CH.Our further study was concentrated on a more accurate proposal of the worst-case comparator which evokes following contra-intuitive behavior:violating a constraint with large weight we are not able to differ assignments violating or satisfying constraints with any smaller weight.This disad-vantage may be eliminated with help of lexicographic ordering which led us to the de?nition of the lexicographic-better comparator.
Even if the CHs are extensively studied and diverse algorithms were discussed to solve particular comparators,any correspondence of CH’s comparators with existing algebraic meta-frameworks wasn’t shown with exclusion of vague statements about their relationship with enhanced versions of fuzzy CSPs.This opens not only a theory gap,but also practical problems which disable the applicability of any general algorithm already proposed.Our ef-fort was devoted to the proposal of instances of particular algebraic structures which would capture most of the discussed comparators.Remaining of them are shown to be incompati-ble with some of the required properties of algebraic structures.As the second step,we have applied our extended de?nitions of equivalence and re?nement between classes of SCSPs and we have classi?ed all comparators of CHs which have an existing counterpart in some class of SCSP.
Basically we have constructed three classes of SCSP:weighted-SCSP corresponding to comparators derived from weighted-sum-better comparator,lexicographic-SCSP for lexic-ographic-better comparator,and local-SCSP for locally-better and ordered-better compara-tors.Worst-case-better comparator does not have its SCSP’s counterpart due to above de-scribed contra-intuitive behavior—this makes the lexicographic-better comparator even mo-re important as its equivalent SCSP class does exist.The property which forbids a proposal of SCSP class for regional comparator is just its ability to compare assignments which are incomparable at higher levels.
Weighted-SCSP together with lexicographic-SCSP are shown to be equivalent with the weighted CSP via polynomial time re?nement.This relationship might be expected because all of them have non-idempotent operator and total ordering of preferences.The total or-dering implies that all comparators dedicated to weighted-SCSP and lexicographic-SCSP classes may be de?ned as a classes of VCSP.However,this doesn’t hold for local-SCSP hav-ing partial ordering of preferences.This class may be polynomially transformed into the weighted CSP but the opposite transformation may not be constructed as the preferences within local-SCSP are partially ordered.
3Variables’Annotations
Above discussed frameworks associate preferences either with constraints or with each tu-ple of values of constraint.An original contribution of the thesis concerns another still not investigated possibility,an idea of assigning preferences to particular variables in constraint. Such preferences may express different levels of importance for particular variables(e.g., time of events within temporal scheduling may be classi?ed by participant’s interest,order of job within jobs’sequence is in?uenced by owner’s priority,prior placement of objects may depend on their properties).
We propose an annotation triple,a structure over annotations de?ning ordering over an-notations and function for combining particular annotations.Local annotations of variables
within constraints are combined to compute global annotations of variables and constraints via speci?ed combining function.Examples of its instances are discussed to be later applied for computing solution via fuzzy annotations,hierarchical annotations,and variable ordering[6].
Fuzzy and hierarchical annotations[2,4,3]present interpretation of variable’s annota-tions based on existing frameworks with preferences,on fuzzy CSP and constraint hierar-chies.For fuzzy annotations,global constraint annotations de?ne preferences for selection of solutions via min-max optimization.A correspondence of constraint system with fuzzy annotation with both fuzzy and possibilistic CSPs is proven.For hierarchical annotations[1], annotated constraint hierarchy(ACH)is constructed with help of global annotations which de-?ne weights of particular constraints.Solution of ACH is computed by different methods inherited by weighted-sum,worst-case,and least-square principles.Another method is pre-sented via individual comparison of particular global annotations at each level.Mapping of applied methods to particular comparators of CH is presented in accordance with se-lection method for global comparators.Solutions obtained via individual comparison are compatible with the proposed ordered-better comparator of CHs.Based on early mentioned algorithm for computing the ordered-better solution of CH,we have implemented a solver for systems of inequalities with annotations.
Another interpretation of annotations considers them as a source for computing variable ordering(VO)in CSPs with preferences.Several methods are proposed including different annotation triples and static versus dynamic VO.While static VO is computed with help of global annotations within initial solving step,dynamic VO recomputes global annotation each time a variable should be instantiated.Such global annotations take into account those variables only which remain to be free wrt.current partial assignment of variables in given computation step.
4Timetabling
The?nal part of the thesis concerns practical application of constraint-based approach with preferences in the area of timetabling[7,5].Our intent is devoted to the course timetabling problem which is a typical representative of scheduling and resource allocation application where various type of preferences need to be involved to obtain any acceptable solution.
First we have introduced general problem considering particular courses,teachers,class-rooms,and students as the basic objects.Having courses with too large number of students, they may be split to course sections.The main tasks to be solved are section assignment(as-sign students to particular course sections),classroom allocation(assign classrooms to course sections),and time assignment(assign time to course sections).
Subsequently our attention is devoted to current solution methods of the classroom alloca-tion and time assignment problems via constrained-based approach.We have distinguished possible models of problem solution including classroom and time assignment variables wrt.problem properties.We have also studied methods for search of solution space wrt. preferences within the problem.Such search might be processed with no global optimiza-tion criteria via labelling heuristics or non-systematic constraint relaxation https://www.doczj.com/doc/8a2964873.html,belling heuristics in?uence solution search by an ordering of variables and values in their domains. Both orderings may re?ect preferences within the problem.Constraint relaxation methods select some of the problem constraints to be violated.Here selection of violated constraints depends on their preferences.More sophisticated approaches de?ne some objective func-
tion over preferences within the problem with aim to optimize its value.This de?nition often leads to the weighted CSP and relaxing the constraints wrt.their weights or costs.
We have studied classroom allocation problem and proposed representation of problem with help of global constraints for distinguished problem instances.The most simple prob-lem de?nition allows to allocate classrooms of the same capacity to courses such that all requirements towards classrooms can be speci?ed over time variables and overall classroom allocation might be processed after completing the time assignment.We have de?ned suf?-cient property of the problem together with its representation by global constraints to allow such separation of classroom allocation and time assignment also for classrooms of various capacities and types.To solve general problem instance,we partitioned classroom allocation to two steps which are processed before and after time assignments.
Next section is devoted to construction of student-oriented schedules representing problem which still was not solved via CP methodology.The?rst part de?nes an objective function over generated timetable minimizing the number of courses which student is not able to attend wrt.parallel schedule of his(her)other course(s).Incremental de?nition of approxi-mation of this objective function allows its inclusion into labelling.The second part de?nes soft disjunctive scheduling problem(SDSP)which instance is also designated student con?ict minimization problem.Solution of such SDSP is de?ned via weighted and fuzzy constraint sat-isfaction as the basic representative of different complexity classes of CSPs with preferences.
Preferences are also included into the problem with help of variables’annotations as over-all problem is stated in variables having their own natural preferences.Annotations are derived from seniority of teachers(dean,professors,assistants,...),type of classrooms,or interest of students expressed by their requirements in course pre-enrollment.These annota-tions are applied via variable ordering methods.Examples of hard and soft constraints with annotations are described?nally.
Proposed methods are applied for Faculty of Informatics timetabling problem which solution was implemented in CLP library of ILOG Scheduler.Overall problem is characterized by requirements of scheduling courses for individual students(more than1000students)and taking into account preferential requirements of teachers towards any acceptable timetable. Achieved computational results conclude this part,within them the most interesting one is a quality of generated timetable satisfying more than94%students’requirements.
Our solution methods together with achieved results are compared with other approaches and solutions of comparable problem instances at the end of chapter.
References
[1]Hana Rudová.Constraints with variables’annotations and constraint hierarchies.In
Branislav Rovan,editor,SOFSEM’98:Theory and Practice of Informatics,pages409–418.
Springer-Verlag LNCS1521,1998.
[2]Hana Rudová.Constraints with variables’annotations.In Henri Prade,editor,13th Eu-
ropean Conference on Arti?cial Intelligence Proceedings,pages261–262.John Wiley&Sons, Ltd.,1998.
[3]Hana Rudová.Constraints with variables’annotations.Technical Report FIMU-RS-98-
04,Faculty of Informatics Masaryk University,1998.
[4]Hana Rudová.Over-constrained systems.In Proceedings of the Sixteenth National Confer-
ence on Arti?cial Intelligence and the Eleventh Innovative Applications of Arti?cial Intelligence Conference,page954.AAAI Press/MIT Press,1999.Presented in1999SIGART/AAAI Doctoral Consortium.
[5]Hana Rudováand Ludˇe k Matyska.Timetabling with annotations.Technical Report
FIMU-RS-99-09,Faculty of Informatics Masaryk University,1999.
[6]Hana Rudováand Ludˇe k Matyska.Uniform framework for solving over-constrained
and optimization problems.In CP’99Post-Conference Workshop on Modelling and Solving Soft Constraints,1999.
[7]Hana Rudováand Ludˇe k Matyska.Constraint-based timetabling with student sched-
ules.In Edmund Burke and Wilhelm Erben,editors,P ATAT2000—Proceedings of the3rd international conference on the Practice And Theory of Automated Timetabling,pages109–123, 2000.
英语单词惯用法集锦 习惯接动词不定式的动词（V to inf) adore(vi极喜欢) dread （vt.不愿做，厌恶）plan 计划 afford（+to,vt有条件，能承担）endeavour （vt，竭力做到，试图或力图）prefer（vt.宁可；宁愿(选择)；更喜欢）agree 同意endure(忍受.cannot ~ to) prepare准备 aim (vi[口语]打算：) engage (vi.保证，担保；) presume(vt.冒昧；敢于[用于第一人称时为客套话]：) appear (vi.似乎；显得) essay(vt.尝试，试图) pretend(vt.自命；自称；敢于；妄为) apply （申请）expect（期望，希望）proceed（开始，着手，）arrange （vi.做安排，(事先)筹划）fail （vt.未做…；疏忽)promise(许诺，保证做 ask （要求）forget （vt. 忘记）purpose （vt.决心，打算） beg （vt.正式场合的礼貌用语]请(原谅)，请(允许)：I beg to differ.恕我不能赞同）guarantee（保证，担保）refuse（拒绝）bear 承受，忍受hate（[口语]不喜欢；不愿意；）regret （vt. 抱歉；遗憾）begin help （有助于，促进）remember（记住） bother （vi.通常用于否定句]麻烦，费心）hesitate（vi.犹豫；有疑虑，不愿）scheme（策划做）care （vt.想要；希望；欲望[后接不定式，常用于否定、疑问及条件句中]）hope （vt.希望，盼望，期待）seek（vt.谋求，图谋[后接不定式]） cease （停止; 不再(做某事)[正式] intend （打算；想要）seem（似乎，好像[后接不定式或从句]；觉得像是，以为[ choose （意愿；选定；决定）itch start开始claim （vt. 主张；断言；宣称） continue （继续）like 喜欢swear（vt.起誓保证；立誓要做(或遵守） dare （vt.敢，敢于，勇于，胆敢）long（vi.渴望；热望；极想） decline（vt.拒绝，拒不(做、进入、考虑等) manage（设法完成某事）threaten（vt.威胁，恐吓，恫吓）deign （屈尊做）mean（有意[不用进行时）trouble（vi.费心，费神；麻烦）demand（vi.要求，请求：）need （需要）try（设法做） deserve (应得) neglect (疏忽) undertake(承诺,答应，保证) desire （希望渴望）offer（表示愿意(做某事)，自愿；）venture（冒险(做某事））determine（vi.决心，决意，决定，）omit （疏忽，忘记）want 想要 die （誓死做）pine （渴望）wish （希望） 习惯接“疑问词+动词不定式”的动词（有时也包括VN wh-+to do) advise 建议explain 解释perceive 觉察，发觉 answer 答复find 得知，察觉persuade 说服，劝说；使某人相信 ask 询问，问forget 忘记phone 打电话 assure 保证guess 臆测，猜度pray 祈祷 beg 请求，恳求hear 小心聆听（法庭案件）promise 允诺 conceive 想象，设想imagine 以为，假象remember记得 consider 考虑，思考indicate 暗示remind 提醒，使想起 convince 使相信inform告知通知instruct告知，教导 see 看看，考虑，注意decide 解决，决定know 学得，得知 show 给人解释；示范；叙述；discover发现；知道learn 得知，获悉 signal以信号表示doubt 怀疑，不相信look 察看；检查；探明 strike 使想起；使突然想到；使认为suggest 提议，建议tell 显示，表明；看出，晓得；warn 警告，告诫think 想出；记忆，回忆；想出，明白wonder 纳闷，想知道 wire 打电报telegraph 打电报 习惯接动名词的动词（包括v+one’s/one+v+ing) acknowledge 认知，承认…之事实escape免除，避免omit疏忽，忽略 admit 承认，供认excuse 原谅overlook 放任，宽容，忽视adore （非正式）极为喜欢fancy 构想，幻想，想想postpone 延期，搁置 advise 劝告，建议finish完成prefer较喜欢 appreciate 为…表示感激(或感谢)forbid 不许，禁止prevent预防 avoid 逃避forget 忘记prohibit 禁止，妨碍
Prefer的用法 最常见的意思是"宁可"、"宁愿(选择)"、"比较喜欢"、"更喜欢"等, 可以构成以下结构。 一. prefer sth. "Do you like French?""Yes, but I prefer English.""你喜欢法语吗?""喜欢,但是我更喜欢英语。" 注:prefer是"比较喜欢,更喜欢"的意思,即like better,因此就不能再与better, more等比较级词语连用。 二.prefer over sth. I prefer over this newly-built lab, and you? 我比较喜欢这个新建的实验室,你呢? They prefer over new works that sing of their life today. 他们更喜欢歌颂他们今天生活的新作品。 三. prefer sth. above all others I prefer the book above all others. 我最喜欢这本书。 四. prefer A to B I prefer the original book to the revised edition. 我觉得原书比修订本好。 五. prefer doing A to doing B Even on holidays Mr. Wang preferred reading to doing nothing. 即使在假日,王先生宁愿读书而不愿闲着。
注:在这种结构中,to为介词,而不是不定式符号,故其后应当接动名词形式,决不能接动词原形。另外,为了保持前后对应关系,prefer后面也应当接动名词形式。 六. prefer to do sth. They prefer to spend the rest of the morning wandering in the streets. 他们比较喜欢把早上剩下的时间都用来在街上闲逛。 七. prefer doing sth. So you prefer speaking without referring to your notes? 这么说,你更喜欢不看稿子做报告了? 注: 这种prefer后面接动名词的结构,用来谈论一般情况下"更喜欢某种活动",而在一个特定场合下表示"特别喜欢"时,得用上述prefer 后接动词不定式结构。 八. prefer to do sth. rather than do sth. These workers prefered to work extra hours at night rather than leave the work until the next week. 这些工人宁愿加班干,也不愿把工作留到下一个星期。 注:这种结构中的rather than可以置于句首。例如: Rather than go on holiday to the seaside I prefer to work days and go to school nights. 我宁愿白天工作,晚上上学,而不愿到海边度假。
1、keep ①keep + 形容词表示“保持” Please keep quite. 请保持安静。 ②keep + 宾语+ 形容词（或介词短语）表示“把……保持在某一状态” We must do everything we can to keep the air clean. 我们必须尽一切所能保持空气清洁。 ③keep sb doing sth 表示“让某人做某事” ——只能用现在分词作宾语补足语，不能用不定式。 He kept us waiting for two hours. 他让我们等了两个小时。 He kept us to wait for two hours. (错误) ④keep on doing sth和keep doing sth 表示“继续做某事，反复做某事”，可换用。 但keep on doing 更强调动作的反复性或做事人的决心。 He keeps on phoning me, but I don’t want to talk to him. Though he failed 3 times, he kept on trying. 他老是给我打电话，但我不想同他讲话。虽然他已失败了3次，但他仍继续干下去。 keep doing sth 经常用于静态动词。 He kept lying in bed all day long. 他整天都躺在床上。 ⑤keep …from doing sth 表示“阻止，使免于” He kept them from fishing in the lake. 他不让他们在那个湖里捕鱼。 2、may not / mustn’t / needn’t / wouldn’t ①may not be 是may be的否定式，意为“可能不是，也许不是” He may be there.他可能在那里。He may not be there.他可能不在那里。 ②must 意为“必须”，mustn’t 意为“千万不可，绝对不可” 所以Must we/I ……?的否定回答要用needn’t—意为“不必” -Must we get there before 11 o’clock？ -No, we needn’t. ③wouldn’t = would not 意为“不会，不愿” I wouldn’t say no. 3、do ①do表示“做”，做某事，常指某种不具体的活动；make表示“制作”，指做出某种具体的东西。
知识点滴：单词prefer 的用法大全 1. prefer+ 名词 ——Would you like meat or fish? ——I'd prefer meat ，please. 2. prefer+ 动名词 Do you prefer cooling for yourself or eating in a restaurant? 自己做饭还是喜欢下馆子？ —Do you like swimming? 你喜欢游泳吗？ —Yes, but I prefer sailing. 喜欢，但我更喜欢驾驶帆船。 3. prefer+ 不定式 Do you prefer to cook for yourself, or to eat in a restaurant? I prefer to spend the weekend at home. 我喜欢在家里度周末。 I would prefer to stay at home tonight. She prefers to be alone. 4. Prefer sb. to do sth. Their father prefers them to be home early. 他们的父亲宁愿他们早点回家。 I thought you would prefer me not to knock. 5. prefer A to B 在本句型中，A与B是平行结构，可以是名词，也可以都是动名词。例如： I prefer dogs to cats. 在狗与猫之间我更喜欢狗。 Most people prefer trains to buses. 大多 数人愿意坐火车而不愿坐汽车。 I prefer writing a term paper to taking an examination. 我宁愿写一篇学期论文也不愿参加考试。 I prefer staying at home to going out. 我觉得在家里比出去好。 Thousands of children nowadays prefer doing their homework to a background of pop-music to doing it in a quiet room. 成千上万的孩子如今一边听流行音乐一边做作业， 也不愿在安安静静的房间里做。 She has always preferred marking her own clothes rather than buying them in the shops. 她向来喜欢自己做衣服，而不到商店里去买衣服。 6. Prefer+ 不定式+rather than+ 不定式 1) 本句型中，第一个不定式前面要加to ，第二个不定式前面以不加to 居多。例如：He prefer to die rather than become traitor. 他宁死也不做叛徒。 Older people often fear change. They know what they can do best. They prefer to repeat their successes rather than risk failure. 年纪大的人常常怕变化。他们知道什么最拿手，宁愿把自己成功的经验再如法炮制也不愿冒失败的危险。 She preferred to sew rather than to knit. 她喜欢缝纫而不喜欢编织。 2) rather than 也可以置于句首： Rather than buy a car of his own, he prefers to rent one. 3) than 后也可用动名词： I prefer to stay at home rather than go/going to see a film. 我觉得与其去看电影倒不如待在家里。 I would prefer to spend the weekend at home rather than drive/driving all the
#pragma code_seg 格式如： #pragma code_seg( [ [ { push | pop}, ] [ identifier, ] ] [ "segment-name" [, "segment-class" ] ) 该指令用来指定函数在.obj文件中存放的节,观察OBJ文件可以使用VC自带的dumpbin命令行程序,函数在.obj文件中默认的存放节为.text节，如果code_seg 没有带参数的话,则函数存放在.text节中。 push (可选参数)将一个记录放到内部编译器的堆栈中,可选参数可以为一个标识符或者节名 pop(可选参数)将一个记录从堆栈顶端弹出,该记录可以为一个标识符或者节名identifier(可选参数)当使用push指令时,为压入堆栈的记录指派的一个标识符,当该标识符被删除的时候和其相关的堆栈中的记录将被弹出堆栈 "segment-name" (可选参数)表示函数存放的节名 例如: //默认情况下,函数被存放在.text节中 void func1() {// stored in .text } //将函数存放在.my_data1节中 #pragma code_seg(".my_data1") void func2() {// stored in my_data1 } //r1为标识符,将函数放入.my_data2节中 #pragma code_seg(push, r1, ".my_data2") void func3() {// stored in my_data2 } int main() { } 例如 #pragma code_seg(“PAGE”) 作用是将此部分代码放入分页内存中运行。 #pragma code_seg() 将代码段设置为默认的代码段 #pragma code_seg("INIT") 加载到INIT内存区域中，成功加载后，可以退出内存
一动词加-ing 的情况 consider, suggest/advise,look forward to, excuse/pardon admit,delay/put off,fancy avoid,miss,keep/keep on,practise deny,finish,enjoy/appreciate forbid,imagine,risk can't help,mind,allow/permit,escape 考虑建议盼原谅, 承认推迟没得想. 避免错过继续练, 否认完成就欣赏. 禁止想象才冒险, 不禁介意准逃亡. 如：建议：advise,suggest,冒险:risk,献身:devote oneself to 二动词后加doing 和加to do sth. 意思不一样的情况 ①remember doing指记住过去做过的事，remember to do指记住将来要做的事，表示“不要忘记”。 ②forget doing表示忘记过去做过的事，forget to do表示“没有想起做某事”。 ③mean doing表示“意味着做某事”，mean to do表示“打算做某事”。 ④regret doing表示对已做过的事感到后悔，regret to do表示对将要做的事表示遗憾。 ⑤stop doing表示“停止做某事”，stop to do是停止做正在做的事以便去做另外一件事，这里的to do不是stop的宾语而是stop的目的状语。 ⑥try doing表示“尝试做某事”，try to do表示“设法、试图做某事”。 ⑦go on doing表示继续做同一件事，go on to do表示做完一件事后，接下去做另外一件事。 三动词后加to do sth. afford负担得起agree同意appear似乎，显得arrange安排 ask问attempt企图beg请求begin开始 choose选择claim要求decide决定demand要求 desire愿望determine决定expect期望fail不能 forget忘记happen碰巧hate憎恨，厌恶hesitate犹豫 hope希望intend想要learn学习long渴望 love爱manage设法mean意欲，打算need需要 neglect忽视offer提供omit忽略，漏other扰乱；烦恼
词组prefer to的用法 prefer A to B I prefer the original book to the revised edition. 我觉得原书比修订本好。 prefer doing A to doing B Even on holidays Mr. Wang preferred reading to doing nothing. 即使在假日,王先生宁愿读书而不愿闲着。 注:在这种结构中,to为介词,而不是不定式符号,故其后应当接动名词形式,决不能接动词原形。另外,为了保持前后对应关系,prefer后面也应当接动名词形式。 prefer to do sth. They prefer to spend the rest of the morning wandering in the streets. 他们比较喜欢把早上剩下的时间都用来在街上闲逛。 prefer doing sth. So you prefer speaking without referring to your notes? 这么说,你更喜欢不看稿子做报告了? 注: 这种prefer后面接动名词的结构,用来谈论一般情况下"更喜欢某种活动",而在一个特定场合下表示"特别喜欢"时,得用上述prefer后接动词不定式结构。 prefer to do sth. rather than do sth. These workers prefered to work extra hours at night rather than leave the work until the next week. 这些工人宁愿加班干,也不愿把工作留到下一个星期。 注:这种结构中的rather than可以置于句首。例如: Rather than go on holiday to the seaside I prefer to work days and go to school nights. 我宁愿白天工作,晚上上学,而不愿到海边度假。 注:有时rather可以移至第一个不定式之前,而让than留在第二个不定式之前,即为prefer rather...than结构.这种用法多见于书面语言,在口语中很少用. prefer to do sth. rather than doing sth. They prefer to join in the celebrations rather than going on a visit to the Palace Museum. 他们宁愿参加庆祝活动而不愿参观故宫。
pretend三种易混淆不定式的用法 今天给大家带来了pretend三种易混淆不定式的用法，我们一起来学习吧，下面就和大家分享，来欣赏一下吧。 pretend三种易混淆不定式的用法 1. pretend to do sth .这个短语的意思是假装(将要)去做什么事情，适用于将来时态动作将来假装要去做但不一定去做的状态。 举例: If youpretend to know what you dont know，youll only make afool of yourself.不懂装懂就会闹笑话。(suri的回答) Child pretend to be mother and father in kindergarten.孩子在幼稚园里面假扮父亲和母亲(表将来)(JasoOon的回答) 2. pretend to have done sth .这个短语的意思是假装已经做过了某事，强调事情的一个完成的状态，侧重于假装的事情已经做好了。 举例:I pretend tohave seen nothing，but I cant.我假装自己没有看到任何东西，但是我做不到(侧重于一个完成时态，已经试图去假装没有看到)
she pretended to have finished the homeworkwhen she went out and played.当她出门玩的时候她假装自己已经完成了家庭作业。(假装做作业这个动作已经在出门玩之前做完了)(JasoOon的回答)以及怀陌的回答:When the teacher came in，he pretended to havefinished the homework.当老师进来的时候他假装自己已经完成家庭作业了，两者有异曲同工之妙。 3. pretendtobe doing sth 这个短语的意思是假装正在做某事，强调动作的一个进行时态。 举例:They pretend to be reading books when the teacher sneakingly stands at the back door.当老师偷偷地站在后门的时候他们假装正在读书(读书与老师站在后门都是过去进行时 态)(JasoOon的回答) Asmanypeople do，youoftenpretend to be doingwork when actuallyyou arejust wasting time online.像很多人一样，你经常假装正在工作，其实是在上网。 群主补充：昨天和今天已提交作业的同学，做得都很好，全部授予小红花。希望你们再接再厉，不要松懈哟。所以下周一出题者为所有已提交作业的同学或者你们选出的代表。
知识点滴: 单词prefer的用法大全 1.prefer+名词 ——Would you like meat or fish? ——I'd prefer meat，please. 2.prefer+动名词 Do you prefer cooling for yourself or eating in a restaurant?自己做饭还是喜欢 下馆子？ —Do you like swimming?你喜欢游泳吗？ —Yes, but I prefer sailing.喜欢，但我更喜欢驾驶帆船。 3.prefer+不定式 Do you prefer to cook for yourself, or to eat in a restaurant? I prefer to spend the weekend at home.我喜欢在家里度周末。 I would prefer to stay at home tonight. She prefers to be alone. 4.Prefer sb. to do sth. Their father prefers them to be home early.他们的父亲宁愿他们早点回家。 I thought you would prefer me not to knock. 5.prefer A to B 在本句型中，A与B是平行结构，可以是名词，也可以都是动名词。例如：
I prefer dogs to cats.在狗与猫之间我更喜欢狗。 Most people prefer trains to buses. 大多数人愿意坐火车而不愿坐汽车。 I prefer writing a term paper to taking an examination. 我宁愿写一篇学期论文也不愿参加考试。 I prefer staying at home to going out. 我觉得在家里比出去好。 Thousands of children nowadays prefer doing their homework to a background of pop-music to doing it in a quiet room.成千上万的孩子如今一边听流行音乐一边做作业，也不愿在安安静静的房间里做。 She has always preferred marking her own clothes rather than buying them in the shops.她向来喜欢自己做衣服，而不到商店里去买衣服。 6.Prefer+不定式+rather than+不定式 1)本句型中，第一个不定式前面要加to，第二个不定式前面以不加to居多。例如：He prefer to die rather than become traitor.他宁死也不做叛徒。 Older people often fear change. They know what they can do best. They prefer to repeat their successes rather than risk failure.年纪大的人常常怕变化。他们知道什么最拿手，宁愿把自己成功的经验再如法炮制也不愿冒失败的危险。 She preferred to sew rather than to knit.她喜欢缝纫而不喜欢编织。 2)rather than也可以置于句首： Rather than buy a car of his own, he prefers to rent one.
UNIT1 Ⅰ.重点单词 1．______________ adj.抽象的；深奥的n．摘要 2．______________n．雕塑 3．______________ n．目标；目的v i.& v t.瞄准；(向某方向)努力 4．______________ adj.卓越的；杰出的；极好的 5．______________n．技术；方法；技能 6．______________ n．巧合(的事)；(事情、口味、故事等)相合 7．______________ n．阴影；影子 8．______________ adj.荒谬的；可笑的 9．______________ adj.争论的；争议的 10．______________n．努力；尝试；企图v t.尝试；企图 11．______________ n．信任；信心；信念→______________ adj.忠诚的→______________ad v.忠实地① 12．______________adj.常规的；传统的；因循守旧的→______________ n．传统② 13．______________ adj.典型的；有代表性的→______________ n．类型 14．______________ adj.明显的；明白的→______________ n．证据③ 15．______________ v t.采用；采纳；收养→______________n．采用；收养④ 16．______________v t.拥有；具有；支配→______________n．拥有；(尤作复数)所有17．______________ v t.预言；预告；预测→______________ n．预告；预言 Ⅱ.核心短语 1．______________ 巧合地 2．______________ 大量 3．_____________ _ (可是)另一方面 4．_____________ _以一种更加现实的方式 5．____________ __ 集中精力于…… 6．____________ _ _导致；通向；通往 7．_____________ _ 逃脱；摆脱；脱离 Ⅰ.重点单词 1．______________ adj.确切的；特定的 2．______________n．画像；身材；数字 3．______________ v t.雕刻；刻记 4．______________ adj.脆弱的；容易生病的；精致的
#pragma预处理命令 #pragma可以说是C++中最复杂的预处理指令了，下面是最常用的几个#pragma 指令： #pragma comment(lib,"XXX.lib") 表示链接XXX.lib这个库，和在工程设置里写上XXX.lib的效果一样。 #pragma comment(linker,"/ENTRY:main_function") 表示指定链接器选项/ENTRY:main_function #pragma once 表示这个文件只被包含一次 #pragma warning(disable:4705) 表示屏蔽警告4705 C和C++程序的每次执行都支持其所在的主机或操作系统所具有的一些独特的特点。例如，有些程序需要精确控制数据存放的内存区域或控制某个函数接收的参数。#pragma为编译器提供了一种在不同机器和操作系统上编译以保持C和C++完全兼容的方法。#pragma是由机器和相关的操作系统定义的，通常对每个编译器来说是不同的。 如果编译器遇到不认识的pragma指令，将给出警告信息，然后继续编译。Microsoft C and C++ 的编译器可识别以下指令：alloc_text，auto_inline，bss_seg，check_stack，code_seg，comment，component，conform，const_seg，data_seg，deprecated，fenv_access，float_control，fp_contract，function，hdrstop，include_alias，init_seg，inline_depth，inline_recursion，intrinsic，make_public，managed，message，omp，once，optimize，pack，pointers_to_members，pop_macro，push_macro，region, endregion，runtime_checks，section，setlocale，strict_gs_check，unmanaged，vtordisp，warning。其中conform，init_seg, pointers_to_members，vtordisp仅被C++编译器支持。 以下是常用的pragma指令的详细解释。 1.#pragma once。保证所在文件只会被包含一次，它是基于磁盘文件的，而#ifndef 则是基于宏的。
Prefer用法 一．prｅfeｒ+名词或动名词“宁愿”,“更喜欢”。He es from Ｓhanghaｉ，ｓo he prefeｒs ricｅ、她就是上海人,因此更喜欢吃米饭。I prｅfeｒ goｉng ｂy biｋｅ、我宁愿骑单车去。Ｉ prefeｒ tｈe whｉte one、我喜欢那个白得. 二。pｒefer ｔo do “宁愿做"．Ｉ pｒefer to gｏ at once、我愿意马上就走。 三。ｐrefer sb、ｔo ｄo “宁愿某人做” I ｐrefｅr ｙoｕ to ｇｏ aｔ oｎce、我倒希望您马上就走. 四.pｒｅｆｅｒＡto B 、“宁愿…而不愿…““喜欢,，,而不喜欢…””与…相比,更喜欢…＂、 I prｅｆeｒ tea to miｌk、我宁愿喝茶也不喝牛奶。I prefｅr watｃｈiｎg TＶ to going oｕt、我宁愿瞧电视也不出去。五。prefer to do sｔｈ、 ratｈeｒｔhaｎ do sｔh、“宁愿做、、、而不做、、、＂ I prefer ｔｏ watcｈ TV ｒａther than ｇo ouｔ、我宁愿呆在家里也不出去. 六．prｅfer+ that从句“宁愿”（从句一般用虚拟语气)I ｐref ｅr thａt ｙou sｈｏuld do iｔ、我宁愿您做这件事. 小结1、pｒefer sth 喜欢某物 2、prefer dｏing stｈ喜欢做某事 ３、ｐrefeｒ sb to do ｓth 喜欢做某事 4、prefeｒ A ｔo B 与Ｂ比起来更喜欢做A
5、prefeｒ doing A to doｉnｇ B 与做B比起来喜欢A 6、prefｅｒ to do Ａ rathｅr thａｎ do B 喜欢做Ａ,不喜 欢作B ７、prｅfer tｏ dｏＡ than do B 喜欢做Ａ,不喜欢作B 练习: 1、I ｐrｅfeｒｗａlｋiｎg alｏne、我喜欢一个人溜达。A:CaｎIｇiｖe youａlifｔ？您顺便坐我得车走吗？ B：Ｎｏ,tｈａnks、I pｒefer to walk、不用了，谢谢，我喜欢步行。 2、Wｅwｏuｌd prefeｒto dｏit ｌａter、我们宁愿以后做它。 ３、A:Wouｌd you ｐrefer tｏwａit? 您愿意等吗？ B：Yｅs,I’d preｆer ｔo、就是得，愿意等． 4、I pｒefｅｒｍy ｃｏffee blａck、我喜欢喝不加奶得咖啡。 5、I preｆeｒthe chａiｒinｉts oldｐｌace、我觉得这把椅子还就是放在老地方好。 6、Ｗe prｅferred ｔｈe hｏuse painｔed white 我们倒喜欢那座漆成白色得房子。 7、Ｔｈeir ｆather ｐrefeｒｓtｈｅm to be hoｍｅｅarly、
#pragma data:code 在Keil中为了节省数据存储器的空间，通过“code”关键字来定义一个数组或字符串将被存储在程序存储器中： uchar code buffer[]={0,1,2,3,4,5}; uchar code string[]="Armoric" ; 而这类代码移值到ICCAVR上时是不能编译通过的。我们可以通过"const" 限定词来实现对存储器的分配： #pragma data:code const unsigned char buffer[]={0,1,2,3,4,5}; const unsigned char string[]="Armoric"; #pragma data:data 注意： 《1》使用ICCAVR6.31时，#pragma data :code ;#pragma data:data ; 这些语法时在"data:cod"、"data:data"字符串中间不能加空格，否则编译不能通过。 《2》const 在ICCAVR是一个扩展关键词，它与ANSIC标准有冲突，移值到其它的编译器使用时也需要修改相关的地方。 在ICCAVR中对数组和字符串的五种不同空间分配： const unsigned char buffer[]={0,1,2,3,4,5}; //buffer数组被分配在程序存储区中 const unsigned char string[]="Armoric" ; //stringp字符串被分配在程序存储区中 const unsigned char *pt //指针变量pt被分配在数据存储区中，指向程序存储区中的字符类型数据 unsigned char *const pt //指针变量pt被分配在程序存储区中，指向数据存储区中的字符类型数据 const unsigned char *const pt //指针变量pt被分配在程序存储区，指向程序存储区中的字符类型数据 unsigned char *pt //指针变量pt被分配在数据存储区中，指向数据存储区中的数据 请问#pragma data:code和#pragma data:data是什么意思？ 前者表示：随后的数据将存贮在程序区，即FLASH区，此区只能存贮常量，比如表格之类。
英语语法顺口溜(巧记). 英语学习 动词为纲“滚雪球” 难易编组抓循环 同类归纳印象深图示介词最直观 混淆多因形音义反义词语成对念 构词方法不可忘习惯用语集中练 词不离句法最好课外阅读莫间断 be 的用法口诀 我用am，你用are，is连着他，她，它； 单数名词用is，复数名词全用are。 变疑问，往前提，句末问号莫丢弃。 变否定，更容易，be后not莫忘记。 疑问否定任你变，句首大写莫迟疑。 时间名词前所用介词的速记歌 年月周前要用in，日子前面却不行。 遇到几号要用on，上午下午又是in。 要说某日上下午，用on换in才能行。 午夜黄昏须用at，黎明用它也不错。 at也用在明分前，说“差”可要用上to， 说“过”只可使用past，多说多练牢牢记， 莫让岁月空蹉跎。 记住f(e)结尾的名词复数 妻子持刀去宰狼，小偷吓得发了慌； 躲在架后保己命，半片树叶遮目光。 巧记48个国际音标 单元音共十二，四二六前中后。 双元音也好背，合口集中八个整。 辅音共计二十八，八对一清又七浊， 四个连对也包括。有气无声清辅音， 有声无气浊辅音，发音特点应掌握。 非谓语动词的一些特殊用法后只接不定式作宾语的一些常用特殊谓语动词动词后，不定式，want, hope和wish， agree, decide, mean, manage, promise, expect, pretend,且说两位算在此， 要记牢，要记住，掌握它们靠自己。
英语学习小窍门 后接动词不定式做宾语补足语省略不定式符号“to”的一些常用特殊动词 一些动词要掌握，have, let和make, 此三动词是使役，“注意”“观察”“听到”see， 还有feel和watch，使用它们要仔细， 后接“宾补”略去“to”，此点千万要牢记 除此之外，还可以掌握“八字言”， 一感feel,二听hear, listen to, 三让have, let, make,四看see, look at, observe, watch 后只接动名词做宾语的一些常用特殊动词 特殊动词接“动名”，使用它们要记清， “放弃”“享受”可“后悔”， “坚持”“练习”必“完成”， “延期”“避免”非“介意” 掌握它们今必行。 动名词在句中的功能及其它 “动名”语法其功能，名词特征有动、形，主宾表定都可作，“动名”、“现分”要认清，“现分”不作“宾”和“主”， 动名作“状”可不行。二词皆可作定语，混为一谈不允许，主谓关系视分词，“动名”一词无此义。 现在分词形式及在句子中的作用（包括过去分词的作用）： 现在分词真好记，动词后面ING。它的作用真不小，可以充当定状表。 还有宾语补足语，忘记此项不可以。 分词做定语的位置及其它 “定分”位置有二条，词前词后定分晓。 单个分词在词前，有时此规有颠倒。 分词短语在词后，“定从”和它互对照。 “现分”动作进行时，“过分”动作完成了。 （注：“定分”：做定语的分词；“定从”：定语从句；“现分”：现在分词；“过分”：过去分词。） 分词做状语在句子中所表示的意义 分词做状语，概有七意义。“ 时间”和“原因”，“结果”与“目的”。 “方式”加“伴随”，“条件”常出席。 且谈其主语，谓语头前的*。 欲要记住它，必须常练习。（*指句子的主语）
prefer的用法总结 prefer的用法1： 可用于多种形式的复合结构(宾语补足语可以是形容词、介词短语、过去分词、不定式等)。如： i prefer my coffee black. 我喜欢喝不加奶的咖啡。 i prefer the chair in its old place. 我觉得这把椅子还是放在老地方好。 we preferred the house painted white 我们倒喜欢那座漆成白色的房子。 their father prefers them to be home early. 他们的父亲希望他们早点儿回家。 prefer的用法2： 用作动词，表示“更喜欢”“宁愿”等，后接动词时，可用不定式或动名词，其区别大致为：表示一般情况用动名词，表示特定动作用不定式。比较： i prefer walking alone. 我喜欢一个人溜达。 a：can i give you a lift? 你顺便坐我的车走吗? b：no, thanks. i prefer to walk. 不用了，谢谢，我喜欢步行。 但是，与would或should连用时，总是表示特定的想法，所以其后总是接不定式。如：
正：we would prefer to do it later. 我们宁愿以后做它。 误：we would prefer doing it later. 另外注意，当would prefer后接不定式被省略时，要注意保留其中的to，如： a：would you prefer to wait? 你愿意等吗? b：yes, i’d prefer to. 是的，愿意等。 prefer的用法3： 其后有时接that从句作宾语，从句谓语动词通常用虚拟语气(用过去式或用should+v)。如： he preferred that such comments should cease. 他希望停止这种议论。 i would prefer it if you didn’t smoke in here. 我希望你不要在这里面吸烟。 prefer的用法4： 表示“宁愿……而不愿……”“喜欢……而不喜欢……”“与……相比，更喜欢……”等，其基本句型是prefer…to…和prefer…rather than…，其搭配习惯如下： (1) 用于prefer…to…时，主要用于比较两个名词或动名词。如： i prefer the seaside to the mountains. 我喜欢海边，不喜欢山区。