journal of parallel and distributed computing52,82 95(1998)
article no.PC981466
Adaptive Virtual Cut-Through as
a Viable Routing Method1
Ho Won Kim,-Hyun Suk Lee,-Sunggu Lee,-and Jong Kim
-Department of Electrical Engineering and Department of Computer Science and Engineering,
Pohang University of Science and Technology(POSTECH),
San31Hyoja Dong,Pohang790-784,
South Korea
Received February14,1997;revised May11,1998;accepted May11,1998 Adaptive virtual cut-through is considered as a viable alternative to
wormhole switching for fast and hardware-efficient interprocessor communica-
tion in https://www.doczj.com/doc/134084846.html,puter simulations are used to show that our
implementation of a minimal-path fully-adaptive virtual cut-through algo-
rithm outperforms both deterministic and adaptive wormhole switching
methods under both uniform random message distributions and clustered dis-
tributions such as the matrix transpose.A hardware-efficient implementation
of adaptive virtual cut-through has been implemented using a semi-custom-
designed router chip that requires only2.30more area than a comparable
deterministic wormhole router chip.A network interface controller chip,
which is crucial to our adaptive virtual cut-through method,has also been
designed and is under fabrication. 1998Academic Press,Inc.
Key Words:Virtual cut-through,wormhole switching,circuit switching,
multicomputer,direct interconnection network,VLSI design.
1.INTRODUCTION
The interconnection network is a critical component of a massively parallel com-puter system because information must be communicated quickly in order for the processing nodes of the parallel computer to cooperate in solving a given problem. Information may be sent as messages between the processing nodes of a distributed-memory multicomputer or as data between the processors and memories of a shared-memory multiprocessor
For fast inter-processor communications,dedicated hardware devices,termed routers,can be used to perform flow control without the intervention of the com-putation processor.Two popular hardware-supported switching methods are 1This paper has been significantly modified from a preliminary version of this work presented at the ``24th International Conference on Parallel Processing''held in August1995.This work was supported
wormhole (WH )switching [1]and virtual cut-through (VCT )switching [1].In WH switching (also known as WH routing)and VCT switching,messages arriving at an intermediate node are immediately forwarded to the next node on the path without buffering,provided that a channel to the next node is available.This is referred to as a cut-through operation.A cut-through may be performed at an intermediate node as soon as the header of the message arrives with the destination information.If cut-throughs are established through all intermediate nodes,a circuit is estab-lished to the destination,and the switching method resembles traditional circuit switching .If the message header is blocked at an intermediate node because the requested outgoing channel is unavailable,the message is kept in the network (i.e.,in the on-line flit buffers at each node along the path up to the current node)in WH and completely buffered at the current node in VCT.
Wormhole switching is the most popular communication method used in current commercial multicomputers due to its low hardware overhead (requiring only a single flit buffer per incoming channel)and high performance.However,VCT can typically achieve higher performance than WH for the following reason:when a packet cannot cut-through an intermediate node,the packet is buffered at that node instead of being kept in the network as in WH.This effect becomes particularly evident with heavy network traffic.The main reason that VCT has not been as popular as WH is that the required buffering capability of the former method has been seen as a large hardware overhead.
Due to its relative unpopularity,VCT has not been as heavily researched as WH.However,this paper will show that VCT,in particular adaptive VCT,has signifi-cant performance benefits over WH and can be implemented with minimal hardware overhead.It is shown that adaptive VCT has several attractive features when compared to WH:negligible overhead for avoiding deadlock (a situation in which no packet can proceed toward its destination),use of 1000of the free channels,good performance with heavy network traffic,and good performance with random or arbitrary locations of destination nodes.The hardware complexity issue is addressed by showing that VCT can be implemented with little hardware over-head (in some cases,less than WH),by exploiting the source buffer in the network interface to the router.
2.BACKGROUND
The type of parallel computer assumed will be a multicomputer with a direct interconnection network ,in which a communication link can only be used by the two end-nodes that it is connected to.Adjacent processing nodes are assumed to be connected by two directed communication links in opposite directions (although undirected links are also possible,directed links are assumed for simplicity).A com-munication link consists of one or more data lines and several control lines.One or more physical channels may occupy a single communication link by using time multiplexing or by partitioning the set of data lines.One or more virtual channels may occupy a single physical channel by using separate flit buffers and control lines 83
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physical channel,they must be time-multiplexed;however,when only one of the virtual channels is active,it can utilize the full bandwidth of the physical channel. It is also assumed that messages are sent in fixed-size packets.
All communication methods must deal with the problem of deadlock,which occurs when there is a cycle of packets in which no packet can progress toward its destination because it is blocked by some other packet.WH switching is par-ticularly susceptible to deadlock because blocked packets remain in the network, thereby reducing the number of free channels.Although much less likely,deadlock is also possible with VCT as the packet buffers at intermediate nodes can become full.The use of virtual channels was introduced by Dally and Seitz[1]as a means of guaranteeing deadlock-free WH switching.The WH routing algorithms intro-duced in[1]are deterministic algorithms,in which the routing path used is com-pletely determined by the source and destination node addresses.In[3],Dally showed that virtual channels could also be used with a deterministic WH routing algorithm to significantly reduce the probability of blocking,and thus increase the throughput of the network.
Realizing the need for adaptability in routing around congested or faulty nodes and links,several researchers[4,5]used virtual channels to produce adaptive deadlock-free WH routing algorithms,in which a packet is permitted to change its routing path if a blocked channel is encountered.Adaptive algorithms can be classified into minimal[6]and nonminimal[4,7]algorithms,where a minimal algorithm always uses the shortest-length paths to each destination,and fully adap-tive[4]and partially adaptive[6,7]algorithms,where the former differs from the latter in that only a subset of the possible paths may be used.
3.ADAPTIVE VIRTUAL CUT-THROUGH
Wormhole switching methods have several deficiencies when compared to VCT. First,WH in general has a lower saturation throughput than a comparable VCT method as blocked packets contribute to network congestion in WH;however,this problem is significantly alleviated by the use of multiple-flit flit buffers and?or multi-ple virtual channels.Second,in WH based on deadlock avoidance,even with the use of virtual channels,1000of the free channels(and flit-buffers)are not available for use by a given packet as some of the channels have to be reserved in order to prevent deadlock.Also,in WH based on deadlock recovery,extra hardware over-head(deadlock buffer,timer,and crossbar)is necessary to detect and recover from deadlock[8 10].Third,fully adaptive routing in torus networks is difficult and requires extra virtual channels to be used for deadlock avoidance.Although virtual channels do not waste channel bandwidth,virtual channels do occupy valuable hardware resources because each virtual channel requires a separate on-line flit buffer and control line and contributes to the complexity of the arbitration logic within the router(refer to Section4).
For the above reasons,adaptive VCT is proposed as an alternative to WH. When originally proposed in[2],VCT was described as a deterministic routing
incoming channel,the header is decoded to determine the ``one''outgoing channel to connect to.If that outgoing channel is busy,then the packet is buffered at the current node.This method is analogous to deterministic WH as originally described by Dally and Seitz [1].Thus,it is natural to consider an adaptive version of virtual cut-through in order to be able to navigate around congested or faulty nodes ?links.In order to facilitate discussion of the many possible forms of adaptive VCT,a general switching model,shown in Fig.1,is proposed.When the head of a packet is received at an incoming channel,the destination node information is extracted from the header.A connection is then attempted to the first-choice outgoing chan-nel.If successful,then a cut-through is established through the current node as denoted by (0)in Fig.1.However,if the requested outgoing channel is blocked (1)because it is being used by another packet,then a connection is attempted to the second-choice outgoing channel (2).This process is repeated until a cut-through is achieved or all outgoing channels permitted by the adaptive VCT algorithm are exhausted,as is the situation in Fig.1.In this situation,the blocked packet remains in the network (as in WH)until one of the permissible outgoing channels becomes available or the ``permitted waiting time''(PWT)expires.In the latter case,the packet is received at the current node (3)and inserted into the source buffer of the current node just as if the packet originated there (the circuit implementation is dis-cussed in Section 4).The packet at the head of the source buffer waits until one of the outgoing channels permitted to it becomes available,and then exits through that outgoing channel,as shown by (4)in Fig.1.The ejection latency out of and the reinjection latency into the network for blocked messages in intermediate nodes are alleviated with the aid of a specially designed network interface controller.
Based on the above switching model,simulations were conducted with several different variations of adaptive VCT.In [11],we showed that deflection VCT ,based on the deflection routing methods proposed for computer networks with packet switching [12],adaptive VCT with PWT>0,and adaptive VCT with the
85
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86KIM ET AL.
choice of adaptivity limited to a fixed number were inferior to adaptive mini-mal-path VCT with PWT=0.In adaptive minimal-path VCT,the packet is permit-ted to choose between all possible minimum-length paths to the destination.Also, within adaptive minimal-path VCT,it is possible to attempt to follow a``zig-zag'' path(algorithm A mc)or to simply follow a``priority-X-direction''path(algorithm A ms).Again,in[11],we showed that A mc performs worse than A ms with certain destination node distributions and is only slightly better than A ms with other destination node distributions.Thus,this paper uses the A ms adaptive minimal-path VCT algorithm,in which the switching model of Fig.1is used and minimal paths are followed with the X-direction attempted first.
The A ms algorithm deals with deadlock in the following manner.Since VCT buff-ers blocked packets,the deadlock conditions for VCT are identical to packet switching thus,the methods used to avoid deadlock in packet switching can be used[13,14].In our hardware implementation of adaptive VCT,the``structured buffer pool technique''for deadlock avoidance[13]was used because of its simplicity.In this method,the source buffer is partitioned into K buffer classes, where K is the diameter of the network.The i th buffer class,also called the i-hop class,may only hold those packets that have i of fewer hops to go to their respec-tive destinations.It is well known that this technique ensures deadlock-free store-and-forward packet switching[13].Our implementation in Section4.3shows that the source buffer can be implemented in a small SRAM(or even main memory) in fact,several researchers are investigating the injection of packets into the network directly from memory,thus avoiding intermediate buffer copies[15,16].The number of buffers in the NIC required to guarantee deadlock freedom is high and depends on the network size.There are other techniques to reduce those buffer requirements to small constant values regardless of network size[17,18]. However,at the time we initiated the NIC design,we were not aware of these techniques.
4.HARDWARE IMPLEMENTATION
https://www.doczj.com/doc/134084846.html,munication Architecture
The proposed communication architecture for supporting adaptive VCT is shown in Fig.2.As can be seen from this figure,there is a network interface controller (NIC),source and receive buffers,and a processor responsible for preparing and sending the packets out onto the network.The NIC is logically partitioned into the external and internal NI.The external NI responds to the network and the internal NI responds to the processor and memory[19].Packets are initially stored in the source buffer before being sent out to the router chip.The router chip is connected to other router chips in a connection pattern determined by the interconnection network topology used.A packet which is injected into a router chip from a pro-cessing node is routed to the router chip connected to the destination node.Packets to be received by the current node are initially buffered in the receive buffer before
https://www.doczj.com/doc/134084846.html,munication architecture.
To demonstrate the feasibility of adaptive VCT,the A ms algorithm was implemented in a semi-custom-designed VLSI router chip and NIC chip.The com-plete hardware implementation of the A ms algorithm in a multicomputer would involve using our router and NIC chips in the network interface.Upon receiving a new packet in the receive buffer,the NIC must examine the header to determine if the packet is destined for the current node or is ``in transit.''In the latter case,the packet must be rerouted to the source buffer to be transmitted when one of its per-mitted outgoing channels becomes available.(Note that bandwidth matching requirements imply that the data transfer rates in the source and the receive buffers must match the data transfer rates within the router network.)In order to perform this rerouting efficiently without having to contend for the local bus,a dedicated path must be established to the source buffer within the external NI arbitration with packet insertion from the local processing node (on a FCFS basis)is of course necessary.
4.2.An Adaptive VCT Router Chip
A block diagram of our router chip,designed to implement the A ms adaptive VCT algorithm in a two-dimensional mesh or torus network,is shown in Fig.3.As can be seen,there are single-flit buffers at the receivers and transmitters and a crossbar switch connecting the receivers to the transmitters.The crosspoint logic includes arbitration logic to handle contention for common transmitters (outgoing channels).Finite state machine control logic in the receiver implements algorithm A ms by first attempting to connect to the first-choice transmitter,then the second-choice transmitter (if one exists),and then the PN (processing node)transmitter (for reception)if none of the first two choices are available.Note that in our prototype chip,6-bit-wide data lines were used to connect to other routers and the local processing node due to a shortage of I ?O pins.Note also that the ``permitted waiting time''used is 0.
The router chip was designed using Mentor Graphics design tools,manufactured using Samsung's 1.0-+m CMOS process,and successfully tested.The arbitration capabilities of the crossbar switch were successfully tested and the A ms adaptive routing algorithm worked as designed.The chip required 33,000transistors,con-87
ADAPTIVE VIRTUAL CUT-THROUGH
FIG.3.Block diagram of the A ms adaptive VCT router chip.
12.5MHz.The layout for this chip is shown in Fig.4.The placement of the various blocks for the router design are approximately the same as in Fig.3.
The hardware overhead required for our adaptive VCT router chip was estimated by measuring the layout area required by our chip as compared to the layout area required by a comparable deterministic WH router chip.This comparison is shown in Table 1.When our chip is compared to a deterministic WH router chip without multiple virtual channels,the overhead is 2.30.When our chip is compared to a deterministic WH router chip with two virtual channels per physical channel (to
88KIM ET AL.
TABLE 1
Router Chip Layout Area Comparison
avoid deadlock),our chip is smaller by 85.00,even though the size of the crossbar is kept constant [3].Since this latter chip has higher performance,however,it should perhaps be compared to an adaptive VCT chip with two virtual channels per physical channel in this case,the overhead for our chip is 9.50.The significance of a smaller chip area is that the router can easily be implemented in one corner of a multiple-capability chip (such as a processor+memory+NIC+router chip).It should be noted,however,that this comparison is only a rough estimate,as the layout is not optimized.
It is noted that in a practical VCT router implementation it is more preferable to use multiple-flit buffers,such as in [20,21],rather than single-flit buffers since single-flit buffers can result in bubbles and reduced throughput.
https://www.doczj.com/doc/134084846.html,work Interface Controller Design
Figure 5shows a block diagram of our NIC chip,which is designed to interface to our router chip and support the A ms adaptive VCT algorithm.The send queue is a queue of ``send packet requests.''If an entry is detected at the head of the send
89
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https://www.doczj.com/doc/134084846.html,yout of the network interface controller chip.
queue,the sending control logic forms a packet header from the destination infor-mation and sends it out followed by the packet body.The packet body is sent out from the source buffer starting at the address pointed to by ``data address.''The receiving control logic,upon receiving the header of a packet,determines if the packet is destined for the current node or is simply being stored temporarily.In the former case,the packet is stored in the receive buffer.In the latter case,the received packet is stored in the source buffer and an entry is appended to the tail of the send queue.The only addition required to the basic NIC design to implement the A ms adaptive VCT algorithm is a flit buffer and some extra control logic to send tem-porarily buffered messages to the source buffer.
In our NIC implementation,the source buffer and receive buffer are implemented as SRAMs with a possible maximum size of 32K words (256words in an internal SRAM and the rest in an external SRAM)and a word size of 6bits (to interface to our 6-bit router chip).Logically,the source buffer is partitioned into two parti-tions.In the first partition,which we arbitrarily chose to be 2K words,packets are stored in any ``packet slot''as they are received.The second partition is sub-parti-tioned into K buffer classes to implement the ``structured buffer pool technique''for deadlock avoidance described at the end of Section 3.This second partition is used only when the first partition is completely filled.Our simulation results at the end of Section 5show,however,that we almost never have to use this second partition.The NIC chip was designed using a 0.8-+m CMOS process and is currently awaiting fabrication.Figure 6shows the layout for the NIC chip.
5.SIMULATIONS
Computer simulations were used to compare the performance of the A ms adaptive 90KIM ET AL.
topologies,network sizes,packet sizes,flit buffer sizes,and multiple virtual chan-nels.A 16_16two-dimensional mesh topology was chosen to allow meaningful comparison with deterministic and adaptive WH routing algorithms as most WH routing algorithms do not work on a two-dimensional torus with only one virtual channel per communication link.Note that the adaptive VCT algorithms,by con-trast,work efficiently (without deadlock)on any network topology,using only one virtual channel per communication link.In the simulations for the A ms algorithm,the ejection and reinjection overhead for an in-transit buffered packet were modeled based on the delays measured with the circuit simulations for our NIC hardware implementation.
In our simulations,a 20-flit packet size is assumed,and packets are transmitted one flit at a time through the network,with one flit being transferred in one clock cycle time.Each node generates new packets according to a Poisson distribution with rate *?L ,where *is the applied load and L is the length of the packets.Destination nodes are selected using two methods,one based on a random uniform distribution and one based on a clustered distribution.Although we have experimented with several clustered distributions,for the sake of brevity only the results for the matrix transpose distribution are shown in this paper.
The simulation results are presented with the offered traffic,*,along the X-axis and the average network latency on the Y-axis.Note that,as in [3],the offered traffic has been normalized by the maximum possible throughput,which on a 16_16mesh with uniform random traffic is 64flits ?cycle.The latency is defined as the time from when a packet is first generated and stored in the source buffer to when the tail of the packet leaves the network and enters the receive buffer of the destination node.All times are measured in terms of flit cycles.Each simulation is executed for 30,000cycles,with statistics collected for only the last 20,000cycles in order to avoid transient startup effects.
FIG.7.Average latency comparison with deterministic and adaptive WH routing algorithms given a 16x16mesh and 20-flit packets,a uniform destination node distribution,2flit buffers per virtual 91
ADAPTIVE VIRTUAL CUT-THROUGH
Figure 7shows a comparison of the A ms algorithm with deterministic and adap-tive WH routing algorithms based on a uniform destination node distribution.The deterministic WH routing algorithm used is the X Y routing algorithm in which the packet is first sent in the X direction and then in the Y direction.The adaptive WH routing algorithms simulated are Glass and Ni's negative-first algorithm based on the turn model [7](NEG),which is a partially-adaptive minimal algorithm,and Disha's WH routing algorithm based on deadlock recovery (Disha-Seq),which is a fully-adaptive algorithm [8,9].The Disha-Seq algorithm is simulated with a time out of 80,the recommended value.At low traffic loads,all methods perform similarly,with Disha-Seq showing slightly better performance than the other algo-rithms.However,when comparing the saturation point,it can clearly be seen that the A ms algorithm has the best performance only the A ms algorithm is capable of supporting a 750traffic load.
Figure 8shows the results for a matrix transpose destination node distribution.With a matrix transpose destination node distribution,the Disha-Seq algorithm again has the best performance at low traffic loads and the A ms algorithm has the highest network saturation point.
Figures 9and 10show the results of using 16virtual channels per communication link (with 32-flit buffers allocated to each virtual channel).The interested reader is referred to [3]and [22]for the effects of larger numbers of virtual channels and larger buffers.Figure 9compares the A ms algorithm with deterministic and adaptive WH routing algorithms assuming 20-flit packets,two virtual channels per link,and a uniform destination node distribution.Figure 10shows a similar comparison assuming a matrix transpose destination node distribution.It can be seen that while the performance of all algorithms have improved significantly from Figs.7and 8,the A ms algorithm again has the highest network saturation point.
FIG.8.Average latency comparison with deterministic and adaptive WH routing algorithms given a 16x 16mesh and 20-flit packets,a matrix transpose destination node distribution,2flit buffers per 92KIM ET AL.
FIG.9.Average latency comparison with deterministic and adaptive WH routing algorithms given a 16x 16mesh,20-flit packets,a uniform destination node distribution,32flit buffers per virtual channel and 16virtual channels per link.
During all simulations with the A ms algorithm,records were kept of the maxi-mum source buffer lengths observed.This is important as our adaptive VCT method is dependent on using the source buffer in the NIC to buffer temporarily blocked packets.The maximum of the source buffer lengths observed under very heavily-loaded network conditions in all of our simulations (taken to be the point when the average latency was over 70times the minimum average latency the network will rarely be used or usable at loads beyond this point)was only 11packets.Thus,in this case,with a packet length of 20flits,a 220-flit source buffer is sufficient to support adaptive VCT.
FIG.10.Average latency comparison with deterministic and adaptive WH routing algorithms given a 16x 16mesh,20-flit packets,a matrix transpose destination node distribution,32flit buffers per 93
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94KIM ET AL.
CONCLUSION
This paper has investigated adaptive VCT as a viable alternative to WH switching. It has been shown that adaptive VCT has several attractive features when compared to WH:negligible overhead for avoiding deadlock(in terms of both performance and hardware),the possibility of using1000of the free buffers and channels,good performance with heavy network traffic,and good performance with uniform or clustered locations of destination nodes.Simulations have been used to investigate the performance of a minimal-path adaptive VCT algorithm(A ms).When compared to other deterministic and adaptive WH routing algorithm,the results show that A ms has a significantly higher network saturation point,and only slightly poorer performance at low network traffic loads.Finally,the hardware complexity issue was addressed by showing that VCT can be implemented with little hardware over-head(in some cases,less than WH)by exploiting the source buffer in the network interface to the router.
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辽宁省五校2018届高三英语上学期期末考试试题 第一部分：听力（共两节，满分30分） 第一节：（共5小题；每小题1.5分^满分7.5分） 听下面5段对话，每段对话后有一个小题，从题中所给的三个选项中选出最佳选项，并标在试卷的相应位置。听完每段对话后，你都有10秒钟的时间来回答和阅读下一小题。每段对话仅读一遍。 例：How much is the shirt? A. ￡19.15. B. ￡9.15. C. ￡9.18. 答案是B。 1. What does the man like about the play? A. The story. B. The ending. C. The actor. 2. Which place are the speakers trying to find? A. A hotel. B. A bank. C. A restaurant. 3. At what time will the two speakers meet? A. 5:20. B. 5:10. C. 4:40. 4. What will the man do? A. Change the plan. B. Wait for a phone call. C. Sort things out. 5. What does the woman want to do? A. See a film with the man. B. Offer the man some help. C. Listen to some great music. 第二节：（共15小题；每小题1.5分，满分22.5分） 听下面5段对话或独白。每段对话或独白后有几个小题。从题中所给的A、B、C三个选项中选出最佳选项，并标在试卷的相应位置。听每段对话或独白前，你将有时间阅读各个小题，每小题5秒钟：听完后，各小题将给出5秒钟的作答时间，每段对话或独白读两遍。 听第6段材料，回答6、7题。 6. Where is Ben?
普通员工辞职申请书范文【三篇】 尊敬的xx人力资源部： 您好! 因为个人职业规划和一些现实因素，经过慎重考虑之后，特此提出离职申请，敬请批准。 在xx工作一年多的时间里，我有幸得到了各位领导及同事们的倾心指导及热情协助，在本职工作和音乐专业技能上，我得到了很大水准的提升，在此感谢xx提供给我这个良好的平台，这个年多的工作经验将是我今后职业生涯中的一笔宝贵财富。 在这里，特别感谢各位领导在过去的工作、生活中给予的大力支持与协助;尤其感谢xx，xx等，一年来对我的信任和关照，感谢所有给予过我协助的同事们。 望批准我的申请，并请协助办理相关离职手续，在正式离开之前我将认真继续做好当前的每一项工作。 祝公司事业蓬勃发展，前景灿烂。 申请人：### 20xx年xx月xx日 【篇二】 尊敬的韩总： 作为一名在酒店工作了大半年的员工，我对酒店有着一种格外亲切的感觉。每一个人在他年轻的时候，都有很多第一次，我当然也不例外。
我的第一份工作是在酒店，我最青春的三年也是在酒店度过的。 在这里，我学会了很多东西，能够跟同事们在一起工作，我觉得很开心，这里的每一位都是我的大哥大姐，我的叔叔阿姨，是他们教给了 我在学校里面学不到的知识，如何为人、如何处事、如何工作……在 酒店里，领导们也对我十分的关心，从刚进入酒店开始，我就感受到 从上至下的温暖。因为我是酒店里年龄还一般，还不算小，也从来没 有在这么大的集体里生活过，自不过然的，心里面就会产生一种被呵 护的感觉。这是一种以前在集体里未曾有过的感觉，很温馨，很自豪，而且它一直陪伴着我，直到我离开…… 但这种感觉不会随着我的离开而走远，我想我永远也不会忘记， 毕竟我以前生活在一个温暖而又温馨的集体里。韩总，还记得第一次 跟您近距离接触和理解是在20xx.3.16号。随着时间的流逝，斗转星移，您多年积累的工作经验与个人才华也得到充分的施展。您是我们 酒店的经理。在我上班之前，制定了一系列的政策与方针，重新定位 了酒店的经营策略，持续地尝试新的机制与奖励、分配办法，力争让 酒店的经济效益持续迈上新高，也让酒店员工的福利待遇如芝麻开花 一般节节高樊。，这才是为员工谋利益的举动，这才是一位被员工在 心里面所认可的经理。 而我，作为这个集体的一份子，更加感觉到您对员工的关心与培养。您肯定想到，酒店要想在竞争激烈的社会中立于不败之地，人才 的培养与发展是不可忽视的环节之一。因为我自身水平的不足，近期 的工作让我觉得力不从心，所以想公司提出了辞呈，忘领导批准。 申请人：### 20xx年xx月xx日 【篇三】 尊敬的公司领导：
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英语高考单项选择 真题部分-2004年浙江省 21. The winner of 1990 was extremely bad. _____ most people say it was the worst winter of their lives. A. At last B.In fact C.In a word D.As a result 22. The Wilsons live in _____ A-shaped house near the coast. It is _____ 17th century cottage. A. the , / B. an, the C. /, the D. an, a 23. The discussion ____ alive when an interesting topic was brought in. A. was coming B. had come C. has come D. came 24. ______ students are required to take part in the boat race. A. Ten strong young Chinese B. Ten Chinese strong young C. Chinese ten young strong D. Young strong ten Chinese 25. We wanted to get home before dark, but it didn’t quite _____ as planned. A. make out B. turn out C. go on D. come up 26. I ____ pay Tracy a visit, but I am not sure whether I will have time this Sunday. A. should B. might C. would D. could 27. ---- What do you want to do next? We have half an hour until the basketball game. ----- _____. Whatever you want to do is fine with me. A. It just depends B. It’s up to you C. All right D. Glad to hear that 28. --- Brad was Jane’s brother! ---_______ he reminded me so much of Jane! A. No doubt B. Above all C. No wonder D. Of course 29. Linda worked for the Minnesota Manufacturing and Mining Company, ____ as 3M. A. knowing B. known C. being known D. to be known 30. If you are feeling so tired, perhaps a little sleep would _____. A. act B. help C. serve D. last 31. _____ modeling business is by no means easy to get into, the good model will always be in demand. A. While B. Since C. As D. If 32. I’ve never seen anyone run so fast---- ______ David go. A. just watch B. just to watch C. just watching D. just having watched 33. We had three sets of garden tools and we seemed to have no use for ______. A. none B. either C. any D. each 34. Because the shop _____, all the T-shirts are sold at half price. A. has closed down B. closed down C. is closing down D. had closed down 35. A nyway, that evening, ____ I’ll tell you more about later, I ended up staying at Rachel’s place. A. when B. where C. what D. Which
2011-2012学年度第一学期高三年级 英语试题 第一部分英语知识运用(共四节,满分55分) 第一节语音知识(共5小题,每小题1分,满分5分) 从每小题的A、B、C、D四个选项中,找出所给单词的正确读音,并在答题卡上将该选项涂黑。、 1. loose A. present B. usual C. usage D. rose 2. south A. courage B. soup C. southern D. trousers 3. official A. concert B. ocean C. coast D. century 4. steam A. hear B. nearly C. mean D. heart 5．judge A．museum B. husband C．true D. huge 第二节情景对话(共5小题,每小题1分,满分5分) 根据对话情景和内容,从对话后所给的选项中选出能填入每一空白处的最佳选项,并在答题卡上将该选项涂黑.选项中有两个为多余选项。 A: Any good news? B: Not really. 6 So I was left behind after school yesterday. A: 7 B: Sometimes I do. The day before yesterday, I was quiet in my history class but I still had to stay after school. A: 8 B: Because I fell asleep. But it wasn’t m y fault. 9 A: I advise you to take school more seriously. If you don’t pass your exam, you will have to drop out and work as a result; B: 10 If I have a job, I have to do dull work every day. But now I am in school, I must listen to dull teachers every day. A: Something must be wrong with you. Go to the psychologist first. A: You are lazy. B: I don’t understand. C: You made your teacher angry. D: Better keep quiet in class. E: The lesson is dull. F: I don’t think it makes much difference. G: I was talking without being asked in class. 第三节语法和词汇知识(共15小题,每小题1分,满分15分) 从每小题的A、B、C、D四个选项中,选出可以填入空白处的最佳选项,并在答题卡上将该选项涂黑。 11.The CEO needs an assistant with ____ little knowledge of German and ___ experience in administrative management. A. the, an B.the, / C. a, an D. a, / 12. Many houses were destroyed in the heavy rain. They should get them _____. A. to repair B. repaired C. repairing D. repair 13. Allow children to voice their opinions, ____ they are different from your own.
辞职报告文本辞职报告范文大全 辞职报告 （篇一） 尊敬的领导： 我很遗憾自己在这个时候向公司正式提出辞职申请。 来到公司也已经快两年了，在这近两年里，得到了公司各位同事的多方帮助，我非常感谢公司各位同事。正是在这里我有过欢笑，也有过泪水，更有过收获。公司平等的人际关系和开明的工作作风，一度让我有着找到了依靠的感觉，在这里我能开心的工作，开心的学习。或许这真是对的，由此我开始了思索，认真的思考。 但是最近我感觉到自己不适合做这份工作，同时也想换一下环境。我也很清楚这时候向公司辞职于公司于自己都是一个考验，公司正值用人之际，公司新的项目的启动，所有的后续工作在公司上下极力重视下一步步推进。也正是考虑到公司今后在这个项目安排的合理性，本着对公司负责的态度，为了不让公司因我而造成的决策失误，我郑重向公司提出辞职。 我考虑在此辞呈递交之后的2—4周内离开公司，这样您将有时间去寻找适合人选，来填补因我离职而造成的空缺，同时我也能够协助您对新人进行入职培训，使他尽快熟悉工作。 能为公司效力的日子不多了，我一定会把好自己最后一班岗，做好工作的交接工作，尽力让项目做到平衡过渡。离开这个公司，离开
这些曾经同甘共苦的同事，很舍不得，舍不得领导们的尊尊教诲，舍不得同事之间的那片真诚和友善。 在短短的两年时间我们公司已经发生了巨大可喜的变化，我很遗 憾不能为公司辉煌的明天贡献自己的力量。我只有衷心祝愿公司的业绩一路飙升!公司领导及各位同事工作顺利! （篇二） 尊敬的办公室人力资源管理领导： 我向公司正式提出辞职。 我自**日进入公司，到现在已经一年有余了，正是在这里我开始 踏上了社会，完成了自己从一个学生到社会人的转变。在过去的一 年多里，公司给予了我许多学习和锻炼的机会，开阔眼界、增长见识。我对公司给予的照顾表示忠心的感谢!但是，经过近段时间的思考， 我越来越迷惘！我越来越觉得现在的工作、生活离自己想要的越来越远。所以，我必须离开，去过我思想深处另一种有别于目前的生活。我想，生活应该是在选择到适合自己的道路以后，再持之以恒地坚持！ 公司目前已经过了一年最忙的时间，是充电、整顿、储备人才的 时刻。相信，我的离开会很快有新生力量补充。因为这不是我想要的工作、生活状态，所以，我现在对工作没有激情、对生活也极其懒散。本着对公司负责的态度，为了不让公司其他同事受到我消极情绪 * ，也为了不让公司因为我出现业务上的纰漏等，我郑重向公司提出辞职，望公司给予批准！ 祝公司稳步发展，祝公司的领导和同事们前程似锦、鹏程万里!
求CSSCI中的垃圾刊物，要好发的 经济问题探索，华东经济管理，商业研究，统计与决策 科技管理研究、图书馆论坛 经济师，财会通讯比较好发。 南京社会科学，现代管理科学 商业研究好投些，统计与决策，管理现代化等等 cssci有些很垃圾的，比如科技管理研究 中国最最最最垃圾CSSCI期刊排行榜＊＊＊＊＊ 从别的网站转过来的，虽然不全了了解，但感觉挺有道理。和大家一起讨论一下。 1 科技管理研究不是C刊＊＊＊＊＊＊＊＊＊ 2 科技进步与对策＊＊＊＊＊＊＊＊科技进步与对策3000字左右1000元 3 生产力研究＊＊＊＊＊＊＊ 4 中国科技论坛＊＊＊＊＊＊＊ ５经济纵横＊＊＊＊＊＊＊＊＊＊ ６财经理论与实践＊＊＊＊＊＊＊ ７经济经纬＊＊＊＊＊＊＊ ８中国国情国力＊＊＊＊＊＊ ９统计与决策＊＊＊＊＊＊＊＊＊ １０求索／江西社会科学／国际贸易问题／旅游科学＊＊＊＊＊＊＊＊＊＊ 中国最最最最垃圾权威期刊排行榜 １财政研究＊＊＊＊＊＊＊＊＊（非学术刊物，一般刊物水平） ２保险研究＊＊＊＊＊＊＊＊＊（非学术刊物，一般刊物水平） ３旅游学刊＊＊＊＊＊＊＊＊＊（非学术刊物，一般刊物水平） ４经济管理．新管理＊＊＊＊＊＊＊＊（自从换成半月刊后，我就再也没有看过了）５投资研究／审计研究＊＊＊＊＊＊＊（不伦不类） ６税务研究＊＊＊＊＊＊＊＊＊＊（非学术刊物，一般刊物水平） ７中国农村经济＊＊＊＊＊＊＊＊＊（社会主义农村大字报） ８人民日报／光明日报／经济日报／求是／马克思主义／科学社会主义／党建研究（尽是怪胎鬼扯，尤其报子上的１８００－２０００来字的空洞废话－－－－－－－－－－－－这些作者全是投机分子，这样的东西敢拿出来当成果并得到了承认确实是中国特色的悲哀和耻辱，闹到关外去绝对是国际笑话）＊＊＊＊＊＊＊＊＊＊＊＊＊＊ 个人认为，国际贸易问题应该是好期刊吧。 个人以为“中国科技论坛”还是有不少好文章的，比“研究与发展管理”要强；“科技进步
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Put the title of your abstract here using both upper and lower case letters, Times New Roman, 12 pts, bold, centered, double spaced A. Author a, B. Author b, C. Author a,* a Department, University, Street, Postal-Code City, Country b Laboratory, Institute, Street, Postal-Code City, Country Abstract This general template helps you on preparing manuscript for part of Elsevier Journals. Use this document as a template if you are using Microsoft Word 6.0 or later. Here comes self-contained abstract. Please read the Guide for Authors of your target journal for the requirements of Abstract. Pay special attention to the word count. PACS(optional, as per journal): 75.40.-s; 71.20.LP Keywords:Keyword 1.D; Keyword 2.B (Read the Guide for Authors for the requirements for Keywords, including number, thesaurus, and classification indications) * Corresponding author. Tel.: +xx xxx xx xx; fax: +xx xxx xx xx. E-mail address: xxxxx@xxx.xx
上师大附中2020 学年度第一学期高三期中考试 英语 考生注意： 1. 考试时间120 分钟，试卷满分140 分。 2. 本考试设试卷和答题纸两部分。所有答題必须涂（选择题）或写（非选择题）在答题纸上，做在试卷上一律不得分。 3. 答題前，务必在答題纸上填写准考证号和姓名。 I. Listening Comprehension Section A Directions: In Section A, you will hear ten short conversations between two speakers. At the end of each conversation, a question will be asked about what was said. The conversations and the questions will be spoken only once. After you hear a conversation and the question about it, read the four possible answers on your paper, and decide which one is the best answer to the question you have heard. 1. A. 7:00 a.m..B. 7:30 a.m..C. 8:00 a.m..D. 8:30 a.m.. 2. A. Parent and child. B. Husband and wife. C. Teacher and student. D. Shop assistant and customer. 3. A. See a doctor about her strained shoulder. B. Use a ladder to help her reach the tea. C. Replace the cupboard with a new one. D. Place the tea on a lower shelf next time. 4. A. At Mary Johnson’s. B. In an exhibition hall. C. At a painter’s studio. D. Outside an a rt gallery. 5. A. He helped Doris build up the furniture. B. Doris helped him arrange the furniture. C. Doris fixed up some of the bookshelves. D. He was good at assembling bookshelves. 6. A. Blue. B. Red. C. Black. D. Green 7. A. He doesn’t get on with the others. B. He has been taken for a fool. C. He doesn’t feel at ease in the firm. D. He has found a better position. 8. A. They’d better not go riding. B. It is not good riding in the rain. C. They can go riding half an hour later. D. Riding a bike is a great idea. 9. A. The man has to get rid of the used furniture. B. The man’s apartment is ready for rent.
广东省清远市清城区高三第一学期期末统考（B）卷 英语试题 (本卷满分150分，时间120分钟) 第一部分听力（共两节，满分30分） 第一节（共5小题；每小题1.5分，满分7.5分） 听下面5段对话。每段对话后有一个小题，从题中所给的A、B、C三个选项中选出最佳选项，并标在试卷的相应位置。听完每段对话后，你都有10秒钟的时间来回答有关小题和阅读下一小题。每段对话仅读一遍。 1．What does the man want to do? A．Fly a kite． B．Go to the park． C．Play on the Internet． 2．What will the girl buy this evening? A．Sunglasses． B．A scarf．C．Gloves． 3．What does the man suggest the woman do? A．Take a taxi．B．Walk to the hotel．C．Ask someone else for help．4．Who is probably the woman? A．A hotel clerk．B．A police officer．C．The man's wife． 5．What are the speakers mainly talking about? A．A birthday party．B．New Year's gifts．C．The man's parents． 第二节(共15小题；每小题1.5分，满分22.5分) 听下面5段对话。每段对话或独白后有几个小题，从题中所给的A、B、C三个选项中选出最佳选项，并标在试卷的相应位置。听每段对话或独白前，你将有时间阅读各个小题，每小题5秒钟；听完后，各小题将给出5秒钟的作答时间。每段对话或独白读两遍。 听第6段材料，回答第6、7题。 6．What is the party for? A．A birthday． B．A graduation ceremony．C．A wedding． 7．Where does the man’s cousin 1ive now?
辞职申请书范文大全500字 辞职申请书500字 辞职一般是提前30天向上级或公司递交辞职，无需公司批准，30天之后您就能顺利辞职了，以下是为大家搜集的范文，欢迎阅读! 尊敬的公司领导： 由于工作调动，现正式向公司提出调离原工作岗位。 舍不得，舍不得这里的人，舍不得自己曾经的付出。每一次出差、每一次报价、每一次谈判、每一次争吵，在飞机上、在吉普车上、在会议室里、在工地上，所有这一切，都充斥着我的记忆，那么清晰，就像是在昨天。但时间的指针总是忠诚地一步一步往前走，昨天终究会结束。 在公司四年半的时间里，我收获了很多，除了朋友和知识，更 重要的是，我到了成长的快乐。感谢命运，让我在最青春的年华里遇到了装备公司;感谢公司领导，你们的关注和欣赏让我一直充满自信，你们的指点和教诲让我在成长的路上少走了很多弯路;感谢公司的同事，和你们的沟通，轻松愉悦;感谢我自己，能够一直保持着一份纯净，真诚地付出，真诚地享受每一次收获。
鉴于目前的身体及生活状态，自认为不能够为公司创造更大的价值，现向公司提出辞职。 虽然我不能在这里继续“战斗”下去，但真心的希望，xx公司能够梦想成真，在世界的舞台上舞出属于自己的精彩。 此致 敬礼! 辞职人： 20xx年xx月xx日 尊敬的x总： 您好! 转眼间，我到公司已有X年了，这X年的工作时间里，虽然我的工作并不是尽善尽美，但在公司同事们的帮助，尤其是您的信任与教导下，我也努力的去完成每一项您布置给我的工作，都用了自己的
热情努力去对待。凭心而论，我开始对基础工程毫无了解，但在您这里我基本了解了基础工程，使我学到了很多东西，特别是一些做人的道理和对生活的理解。在这里，我真诚的对袁总说一声：谢谢您了! 但犹豫再三，经过了长时间的考虑，我还是写了这封辞职申请书。 加入公司以来，您对我的信任、教导与严格要求，令我非常感动，也成为激励我努力工作的动力。在您及同事们的热心指导与悉心帮助下，我在工程技术和管理能力方面都有了一定的提高。我常想，自己应该用一颗感恩的心，去回报您及公司对我的栽培，真的想用自己的努力去做好您交给的每一份工作任务，但自己的能力真的很有限，有很多地方没有做得能让您满意，所以对过去工作中失误与不足的地方，我真诚的对您说声抱歉，请您原谅! 经过这段时间的思考，我觉得我可能技术能力方面有所不足， 也缺少工作的积极性和脚踏实地的工作精神，没能很好的适应这个工作，所以一直没有把工作做到令您满意的程度。这是我在以后的人生中需要注意的地方，也是袁总经常教导我的地方，我一定会铭记于心! 再一次真诚地感谢您及公司全体同事对我的关爱与帮助!
刊物汇总CSSCI 经济问题探索，华东经济管理，商业研究，统计与决策 科技管理研究、图书馆论坛 经济师，财会通讯比较好发。 南京社会科学，现代管理科学 商业研究好投些，统计与决策，管理现代化等等 cssci有些很垃圾的，比如科技管理研究 中国最最最最垃圾CSSCI期刊排行榜＊＊＊＊＊ 从别的网站转过来的，虽然不全了了解，但感觉挺有道理。和大家一起讨论一下。 1 科技管理研究不是C刊＊＊＊＊＊＊＊＊＊ 2 科技进步与对策＊＊＊＊＊＊＊＊科技进步与对策3000字左右1000元 3 生产力研究＊＊＊＊＊＊＊ 4 中国科技论坛＊＊＊＊＊＊＊ ５经济纵横＊＊＊＊＊＊＊＊＊＊ ６财经理论与实践＊＊＊＊＊＊＊ ７经济经纬＊＊＊＊＊＊＊ ８中国国情国力＊＊＊＊＊＊ ９统计与决策＊＊＊＊＊＊＊＊＊ １０求索／江西社会科学／国际贸易问题／旅游科学＊＊＊＊＊＊＊＊＊＊ 中国最最最最垃圾权威期刊排行榜 １财政研究＊＊＊＊＊＊＊＊＊（非学术刊物，一般刊物水平） ２保险研究＊＊＊＊＊＊＊＊＊（非学术刊物，一般刊物水平） ３旅游学刊＊＊＊＊＊＊＊＊＊（非学术刊物，一般刊物水平） ４经济管理．新管理＊＊＊＊＊＊＊＊（自从换成半月刊后，我就再也没有看过了）５投资研究／审计研究＊＊＊＊＊＊＊（不伦不类） ６税务研究＊＊＊＊＊＊＊＊＊＊（非学术刊物，一般刊物水平） ７中国农村经济＊＊＊＊＊＊＊＊＊（社会主义农村大字报） ８人民日报／光明日报／经济日报／求是／马克思主义／科学社会主义／党建研究（尽是怪胎鬼扯，尤其报子上的１８００－２０００来字的空洞废话－－－－－－－－－－－－这些作者全是投机分子，这样的东西敢拿出来当成果并得到了承认确实是中国特色的悲哀和耻辱，闹到关外去绝对是国际笑话）＊＊＊＊＊＊＊＊＊＊＊＊＊＊ 个人认为，国际贸易问题应该是好期刊吧。 个人以为“中国科技论坛”还是有不少好文章的，比“研究与发展管理”要强；“科技进步与对策”则是一篇有用的文章都没有，应该再加两个星。 接受电子投稿的CSSCI来源期刊(经济管理类) [复 中国科技论坛 管理现代化 中国行政管理 中国人力资源开发 hrdchina@https://www.doczj.com/doc/134084846.html, 未来与发展 科技进步与对策 马克思主义与现实
2019-2020学年第一学期上大附中高一英语 9月周日小测 Ⅰ. Grammar Directions: After reading the passage below, fill in the blanks to make the passages coherent and grammatically correct. For the blanks with a given word, fill in each blank with the proper form of the given word; for the other blanks, use one word that best fits each blank. Last August Susan and forty-two other students got wet and dirty while removing six tons of garbage __21__ the rive running across their city. They cleaned up the rive as part of a week-long environmental camp. Like one in three American rives, this river is so polluted __22__ it’s not safe for swimming or fishing. Still, Susan, who __23__ (complete) her third summer camp so far on the river cleanup, sees a change in this river. “Since we started three years ago, the river is getting a lot __24__ (clean).” she says. Environmental scientists praise the teenagers for removing garbage __25__ can harm wild life. Water birds, for example, __26__ die of plastic bottle rings and get cut by tiny metals. Three years ago, __27__ the cleanup started, garbage was everywhere. But this year the teenagers can row their boats fast. By the end of this year’s six-hour cleanup, they __28__ (remove) enough garbage to fill more than two large trucks. “__29__ (see) all that garbage in the rive makes people begin to care about environmental issues,” Susan says. She hopes that when others read that, she and her peers care enough __30__ (clean) it up, maybe they would think twice before they throw garbage into the river. Ⅱ. Vocabulary Directions: Complete the following passage by using the words in the box. Each word can only be used once. Note that there is one word more than you need. 1 / 10
2019—2020学年度高三校际联合检测 英语 2020．01 本试卷共三部分，共10页。满分120分。考试时间100分钟。 注意事项： 1．答卷前，考生务必将自己的姓名、考生号等填写在答题卡和试卷指定位置上。 2．回答选择题时，选出每小题答案后，用铅笔把答题卡上对应题目的答案标号涂黑。如需改动，用橡皮擦干净后，再选涂其他答案标号。回答非选择题时，将答案写在答题卡上。写在本试卷上无效。 3．考试结束后，将答题卡上交。 第一部分阅读(共两节，满分50分) 第一节(共15小题；每小题2.5分，满分37.5分) 阅读下列短文，从每题所给的A、B、C、D四个选项中选出最佳选项。 A Barbican Art Gallery A world-class arts and learning center，the Barbican pushes the boundaries of all major art forms including dance，film，music，theater and many visual arts from Egypt．Tickets： Adult：￡10 online／￡12 at the door 13-17 years old：￡6 online／￡8 at the door Children aged 12 and under：Free Opening Times： Sat．—Wed．：10 a．m．—6 p．m．；Thu．—Fri．：10 a．m．—9 p．m． Review by Laura Miller：I have just watched To Kill a Mockingbird here．The play and actors were fantastic．Nice and clean ladies’toilets with hot water．During the interval，they were selling the usual ice cream and drinks．Not all staff were friendly，but most were．I would come again to watch another show or even the same one． The British Museum
简短辞职申请书范文大全 想必每一位在职场混迹多年的职场人士都应曾经写过辞职信之类的。在现在这个发展速度如此之快的社会，跳槽也就成了常见现象。而离职前的辞职信是必写的。下面就是小编给大家带来的简短辞职申请书范文大全，希望大家喜欢! 尊敬的xx： 我自xx年来到公司，工作中得到公司和您的培养，个人得到了很大的成长，公司的文化和环境也令我工作得非常开心。 现由于个人原因，我不得不提出辞职，希望能于x年x月x日正式离职，请公司批准我的这份辞职书。并请公司在x月x日前安排好人员接替我的工作，我将尽心交接。 再次对您x年来的培养和指导表示衷心的感谢。 最后祝您及公司的所有同事一切顺利! 此致 敬礼 辞职人：xxx 20xx年x月x日 尊敬的X经理： 您好! 感谢公司在我入职以来的培养关心和照顾，从X年X月份来到[公司]至今，我学到了很多东西，今后无论走向哪里，从事什么，这段经历都是一笔宝贵的财富，我为在彩卡的这段工作经历而自豪。 而今，由于个人原因提出辞职，望领导批准。 辞职人： 20xx年x月x日
公司人事部： 我因为要去美国留学，故需辞去现在的工作，请上级领导批准。 公司的企业文化感化了我，我对公司是深有感情的。我留学归来之后，仍愿意回公司就职。 感谢公司领导和同事在工作中对我的关心和支持，并祝公司兴隆。 辞职人：xxx 20xx年x月x日 尊敬的公司领导： 在递交这份辞呈时，我的心情十分沉重。现在由于我的一些个人原因的影响，无法为公司做出相应的贡献。因此请求允许离开。 当前公司正处于快速发展的阶段，同事都是斗志昂扬，壮志满怀，而我在这时候却因个人原因无法为公司分忧，实在是深感歉意。 我希望公司领导在百忙之中抽出时间受理我的离职事项。 感谢诸位在我在公司期间给予我的信任和支持，并祝所有同事和朋友们在工作和活动中取得更大的成绩。 辞职人： 20xx年x月x日 尊敬的xx： 自xx年入职以来，我一直很喜欢这份工作，但因某些个人原因，我要重新确定自己未来的方向，最终选择了开始新的工作。 希望公司能早日找到合适人手开接替我的工作并希望能于今年5月底前正式辞职。如能给予我支配更多的时间来找工作我将感激不尽，希望公司理解!在我提交这份辞呈时，在未离开岗位之前，我一定会尽自己的职责，做好应该做的事。 最后，衷心的说：“对不起”与“谢谢”! 祝愿公司开创更美好的未来!