Multi-threading - Token Bucket Emulation in C
You will emulate/simulate a traffic shaper that transmits/services packets controlled by a token bucket filter depicted below using multi-threading within a single process. If you are notamiliar with pthreads, you should read the textbook.
Multi-threading - Token Bucket Emulation in C
Figure 1 above depicts the system you are required to emulate. The token bucket has a capacity(bucket depth) of B tokens. Tokens arrive into the token bucket according to an unusual arrivalprocess where the inter-token-arrival time between two consecutive tokens is 1/r. We willcall r the token arrival rate (although technically speaking, it's not exactly the token arrivalrate; please understand that this is quite different from saying that the tokens arrive at a constantrate of r). Extra tokens (overflow) would simply disappear if the token bucket is full. A tokenbucket, together with its control mechanism, is referred to as a token bucket filter.Packets arrive at the token bucket filter according to an unusual arrival process where the interarrival time between two consecutive packets is 1/lambda. We will call lambda the packet rrival rate (although technically speaking, it's not exactly the packet arrival rate; please
understand that this is quite different from saying that the packets arrive at a constant rateof lambda). Each packet requires P tokens in order for it to be eligiable for transmission. (Packetsthat are eligiable for transmission are queued at the Q2 facility.)When a packet arrives, if Q1 is not empty, the packet will just get queued onto the Q1 facilitysince packets must be processed in the first-come-first-serverd order. (Please note that, in this case, you do not have to check if there is enough tokens in the bucket so you can move thepacket at the head of Q1 into Q2 and you need to understand why you do not need to performsuch a check.)Otherwise (i.e., Q1 is empty), you must check to see if the token bucket has P or more tokens in
- If the token bucket has P or more tokens in it, you must remove P tokens from the tokenbucket and move the packet into Q2 (although technically speaking, you are required to first addthe packet to Q1 and timestamp the packet, remove the P tokentsfrom the token bucket and thepacket from Q1 and timestamp the packet, before moving the packet into Q2 and get anothertimestamp for the packet), and wake up the servers in case they are sleeping. On the other hand,if the token bucket does not have enough tokens, the packet getsqueued into the Q1 facility.Finally, if the number of tokens required by a packet is larger than the bucket depth, the packetmust be dropped and not get added to Q1 (otherwise, it will block all other packets that follow
it).The transmission facility (denoted as S1 and S2 in the above figure and they are referred to as the
"servers") serves packets in Q2 in the first-come-first-served order and at a transmission/service
rate of mu per second. When a server becomes available, it will dequeue the first packet
from Q2 and start transmitting/servicing the packet. When a packet has received 1/mu seconds of
service, the packet leaves the system. You are required to keep the servers as busy as possible.
When a token arrives at the token bucket, it will add a token into the token bucket. If the
bucket is already full, the token will be lost. It will then check to see if Q1 is empty. If Q1 is not
empty, it will see if there is enough tokens to make the packet at the head of Q1 be eligiable for
transmission (packets in Q1 must be served in the first-come-first-served order). If it does, it will
remove the corresponding number of tokens from the token bucket, remove that packet
from Q1 and move it into Q2, and wake up the servers in case they are sleeping. Please note that
under this scenario, the token bucket must be empty at this time and there would be no need to
check to see if the packet now at the head of Q1 is eligible for transmission or not.
Technically speaking, the "servers" are not part of the "token bucket filter". Nevertheless, it's part
of this assignment to emulation/simulation the severs because the servers are considered part of
the "system" to be emulated. (For the purpose of this spec, we will use the term "emulation" and
"simulation" interchangeably.)
Our system can run in only one of two modes.
Deterministic : In this mode, all packet inter-arrival times are equal to 1/lambda seconds and all
transmission/service times are equal to 1/mu seconds (both these values must
be rounded to the nearest millisecond), and all packets requireexactly P tokens. If 1/lambda is greater than 10 seconds, please use an interarrival time of 10 seconds. If 1/mu is greater than 10 seconds, please use a
transmission/service time of 10 seconds.Trace-driven : In this mode, we will drive the emulation using a trace specification file (will bereferred to as a "tsfile"). Each line in the trace file specifies the inter-arrival time of代 写Multi-threading - Token Bucket Emulation in C a packet, the number of tokens it need in order for it to be eligiable for
transmission, and its transmission/service time. (Please note that in this mode, it's perfectly fine if an inter-arrival time or a transmission/service time is greaterthan 10 seconds.) If you are running in the trace-drive mode, youmust not validate or read the entire tsfile before you start your simulation
because that would delay the start of simulation.In either mode, if 1/r is greater than 10 seconds, please use an inter-token-arrival time of 10seconds. Otherwise, please round the inter-token-arrival time to the nearest millisecond.
Your job is to emulate the packet and token arrivals, the operation of the token bucket filter, the
first-come-first-served queues Q1 and Q2, and servers S1 and S2. You also must produce a trace
of your emulation for every important event occurred in your emulation. Please see more
details below for the requirements.
You must use:
- one thread for packet arrival
- one thread for token arrival
- one thread for each server
You must not use one thread for each packet.
In addition, you must use at least one mutex to protect Q1, Q2, and the token bucket. (It is
recommended that you use exactly one mutex to protect Q1, Q2, and the token bucket.)
Finally, Q1 and Q2 must have infinite capacity (i.e., you should use My402List from previous
assignment to implement them and not use arrays).
Please use a Makefile so that when the grader simply enters:
make warmup2
an executable named warmup2 is created (minor variation is permitted if you document it).
Commandline
The command line syntax (also known as "usage information") for warmup2 is as follows:
warmup2 [-lambda lambda] [-mu mu] [-r r] [-B B] [-P P] [-n num] [-t
tsfile]
Square bracketed items are optional. You must follow the UNIX convention that commandline
options can come in any order. (Note: a commandline option is a commandline argument that
begins with a - character in a commandline syntax specification.) Unless otherwise specified,
output of your program must go to stdout and error messages must go to stderr.
The lambda, mu, r, B, and P parameters all have obvious meanings (according to the description
above). The -n option specifies the total number of packets to arrive. If the -t option is specified, tsfile is a trace specification file that you should use to drive your emulation. In this
case, you should ignore the -lambda, -mu, -P, and -n commandline options and run your
emulation in the trace-driven mode. You may assume that tsfile conforms to the tracefile
format specification. (This means that if you detect an error in this file, you may simply print an
error message and call exit() to quit your program, even if you have started your simulation.
You must not try to perform error recovery if the input file does not conform to the tracefile
format specification.) If the -t option is not specified in the commandline, you must run your
emulation in the deterministic mode.
The default value (i.e., if it's not specified in a commandline option) for lambda is 1 (packets per
second), the default value for mu is 0.35 (packets per second), the default value for r is 1.5
(tokens per second), the default value for B is 10 (tokens), the default value for P is 3 (tokens),
and the default value for num is 20 (packets). B, P, and num must be positive integers (i.e., > 0)
with a maximum value of 2147483647 (0x7fffffff). lambda, mu, and r must be positive real
numbers (i.e., > 0).
Running The Code and Program Output
The emulation should go as follows. At emulation time 0, all 4 threads (arrival thread, token
depositing thread, and servers S1 and S2 threads) got started. The arrival thread would sleep so
that it can wake up at a time in an attempt to match the inter-arrival time of the first packet (i.e.,
either according to lambda or line 2 of a tracefile). At the same time, the token depositing thread
would sleep so that it can wake up at a time in an attempt to match the inter-token-arrival time
between consecutive tokens (i.e., 1/r seconds) and would try to deposit one token into the token
bucket each time it wakes up. The actual arrival time of the first packet p1 is denoted as time T1,
the actual arrival time of the 2nd packet p2 is denoted as time T2, and so on.
As a packet or a token arrives, or as a server becomes free, you need to follow the operational
rules of the token bucket filter. Since we have four threads accessing shared data structures, you
must use the tricks you learned from Chapter 2 related lectures. Please also check out the slides
for this assignment for the skeleton code for these threads.
You are required to produce a detailed trace for every important event occurred during the
emulation and every such event must be timestamped. Each line in the trace must correspond to
one of the following situations:
If a packet is served by a server (server S1 is assumed below for illustration),
there must be exactly 7 output lines that correspond to important events related to this
packet. They are (please see the operational rules of the token bucket filter regarding the
meaning of these events):
- p1 arrives, needs 3 tokens, inter-arrival time = 503.112ms
- p1 enters Q1
- p1 leaves Q1, time in Q1 = 247.810ms, token bucket now has 0 token
- p1 enters Q2
- p1 leaves Q2, time in Q2 = 0.216ms• p1 begins service at S1, requesting 2850ms of service
p1 departs from S1, service time = 2859.911ms, time in system =
3109.731ms
Please note the following:
o The value printed for "inter-arrival time" must equal to the timestamp of the
"p1 arrives" event minus the timestamp of the "arrives" event for the previous
packet. (You can assume that packet p0 arrived at time 0, even though there is no
packet p0.)
o The value printed for "time in Q1" must equal to the timestamp of the "p1
leaves Q1" event minus the timestamp of the "p1 enters Q1" event.
o The value printed for "time in Q2" must equal to the timestamp of the "p1
leaves Q2" event minus the timestamp of the "p1 enters Q2" event.
o The value printed for "requesting ???ms of service" must be the requested
service time (which must be an integer) of the corresponding packet.
o The value printed for "service time" must equal to the timestamp of the "p1
departs from S1" event minus the timestamp of the "p1 begins service at
S1" event (and it should be larger than the requested service time printed for the
"begin service" event).
o The value printed for "time in system" must equal to the timestamp of the "p1
departs from S1" event minus the timestamp of the "p1 arrives" event.
- If a packet is dropped, you must print:
p1 arrives, needs 3 tokens, inter-arrival time = 503.112ms, dropped
Please note that the value printed for "inter-arrival time" must equal to the timestamp of
the "p1 arrives" event minus the timestamp of the "arrives" event for the previous packet.
- If <Ctrl+C> is pressed by the user, you must print the following (and print a '\n' before it
to make sure that it lines up with all the other trace printouts):
SIGINT caught, no new packets or tokens will be allowed
Please understand that in order for the above to get printed correctly in a trace printout,
using a signal handler to catch signals may not work. You are strongly advised to use a
separate SIGINT-catching thread and uses sigwait() (which is covered in Chapter 2).
- If a packet is removed when it's in Q# (Q1 or Q2) because <Ctrl+C> is pressed by the
user, you must print:
p1 removed from Q#
- If a token is accepted, you must print:
token t1 arrives, token bucket now has 1 token• If a token is dropped, you must print:
token t1 arrives, dropped
- When you are ready to start your emulation, you must print:
emulation begins
- When you are ready to end your emulation, you must print:
emulation ends
All the numeric values above are made up. You must replace them with the actual packet
number, actual number of tokens required, actual server number, measured inter-arrival time,
measured time spent in Q1, actual number of tokens left behind when a packet is moved into Q2,
measured time spent in Q2, measured service time, and measured time in the system.
The output format of your program must satisfy the following requirements.
- You must first print all the emulation paramters. Please see the sample printout for what
the output must look like.
- Whenever a token arrives, you must assign a token number to it, and add it to the token
bucket. You must then print its arrival time, the fact that it has arrived, and the number of
tokens in the the token bucket. Please see the sample printout for what the output must
look like.
- Whenever a packet arrives, you must assign a packet number to it. You must then print its
arrival time, the fact that it has arrived, the number of tokens it needs for transmission,
and the time between its arrival time and the arrival time of the previous packet. Please
see the sample printout for what the output must look like.
You then must append this packet onto Q1. Afterwards, you must then print the time this
packet entered Q1 and the fact that it has entered Q1. Please see the sample printout for
what the output must look like.
Later on, when this packet leaves Q1, it removes the correct number of tokens from the
token bucket. You must then print the time this packet leaves Q1, the fact that it has
left Q1, the amount of time it spent in Q1, and the number of tokens in the the token
bucket. Please see the sample printout for what the output must look like.
You must then append this packet onto Q2. Afterwards, you must then print the time this
packet entered Q2 and the fact that it has entered Q2. Please see the sample printout for
what the output must look like.
Later on, when this packet leaves Q2 and enters the server, you must then print which
server the packet entered, the time the packet begin service, the fact that it has begun service, and the amount of time it spent in Q2. Please see the sample printout for what the
output must look like.
- When emulation ends, you must print all the necessary statistics. Please see the sample
printout for what the output must look like. If a particular statistics is not applicable (e.g.,
will cause divide-by-zero error), instead of printing a numeric value, please print "N/A"
followed by an explanation (such as, for example, "no packet was served"). Please note
that your program output must never contain any "NaN" (which means "not-a-number").
Sample Printout: Here is what your program output must look like (values used here are just a
bunch of unrelated random numbers for illustration purposes):
Emulation Parameters:
number to arrive = 20
lambda = 2 (print this line only if -t is not specified)
mu = 0.35 (print this line only if -t is not specified)
r = 4
B = 10
P = 3 (print this line only if -t is not specified)
tsfile = FILENAME (print this line only if -t is specified)
00000000.000ms: emulation begins
00000250.726ms: token t1 arrives, token bucket now has 1 token
00000501.031ms: token t2 arrives, token bucket now has 2 tokens
00000503.112ms: p1 arrives, needs 3 tokens, inter-arrival time = 503.112ms
00000503.376ms: p1 enters Q1
00000751.148ms: token t3 arrives, token bucket now has 3 tokens
00000751.186ms: p1 leaves Q1, time in Q1 = 247.810ms, token bucket now has 0 token
00000752.716ms: p1 enters Q2
00000752.932ms: p1 leaves Q2, time in Q2 = 0.216ms
00000752.982ms: p1 begins service at S1, requesting 2850ms of service
00001004.271ms: p2 arrives, needs 3 tokens, inter-arrival time = 501.159ms
00001004.526ms: p2 enters Q1
00001005.615ms: token t4 arrives, token bucket now has 1 token
00001256.259ms: token t5 arrives, token bucket now has 2 tokens
00001505.986ms: p3 arrives, needs 3 tokens, inter-arrival time = 501.715ms
00001506.713ms: p3 enters Q1
00001507.552ms: token t6 arrives, token bucket now has 3 tokens
00001508.281ms: p2 leaves Q1, time in Q1 = 503.755ms, token bucket now has 0 token
00001508.761ms: p2 enters Q2
00001508.874ms: p2 leaves Q2, time in Q2 = 0.113ms
00001508.895ms: p2 begins service at S2, requesting 1900ms of service
...
00003427.557ms: p2 departs from S2, service time = 1918.662ms, time in system = 2423.286ms
00003612.843ms: p1 departs from S1, service time = 2859.861ms, time in system = 3109.731ms
...
????????.???ms: p20 departs from S?, service time = ???.???ms, time in system = ???.???ms
????????.???ms: emulation ends
Statistics:
average packet inter-arrival time = <real-value>
average packet service time = <real-value>
average number of packets in Q1 = <real-value>
average number of packets in Q2 = <real-value>
average number of packets at S1 = <real-value>
average number of packets at S2 = <real-value>
average time a packet spent in system = <real-value>
standard deviation for time spent in system = <real-value>
token drop probability = <real-value>
packet drop probability = <real-value>In the Emulation Parameters section, please print the emulation parameters specified by the user
or the default values mentioned above. Please do not print the "adjusted" values because certain
parameters are too small. (For example, if lambda is 0.01, you must print 0.01 and not 0.1.)
After Emulation Parameters section comes the Event Trace section. The first column there
contains timestamps and they correspond to event times, measured relative to the start of the
emulation. Every emulation event must be timestampted. You need to figure out how to make
sure that the timestamp values look reasonable (e.g., never decrease in value). Please use exactly
8 digits (zero-padded) to the left of the decimal point and exactly 3 digits after the decimal
point (zero-padded) for all the timestamps in this column. All time intervals in the trace
printout must be printed in milliseconds with exactly 3 digits after the decimal point (zero
padded). Please remember that a time interval in the trace printout is the difference between two
timestamps and timestamps are considered integers with a resolution of microseconds.
Therefore, you must print all the digits. If your code represent timestamps as double, you need to
make sure that you satisfy this requirement or you may end up losing a lot of points. In the
printout, after emulation parameters, all values reported must be measured values.
In the Statistics section, the average number of packets at a facility can be obtained by adding
up all the time spent at that facility (for all relevant packets) divided by the total emulation time.
The time spent in system for a packet is the difference between the time the packet departed
from the server and the time that packet arrived. The token drop probability is the total number
of tokens dropped because the token bucket was full divided by the total number of tokens that
was produced by the token depositing thread. The packet drop probability is the total number
of packets dropped because the number of tokens required is larger than the bucket depth divided
by the total number of packets that was produced by the arrival thread.
All real values in the Emulation Parameters and Statistics sections must be printed with at least 6
significant digits. (If you are using printf(), you can use "%.6g". Please note that with
"%.6g", printf() would omit trailing zeroes.) A timestamp in the beginning of a line of trace
output must be in milliseconds with exactly 8 digits (zero-padded) before the decimal point and
exactly 3 digits (zero-padded) after the decimal point. Please note that the timestamps must
lined up perfectly and have microsecond resolution and the grader needs to see all these
digits.
Please use sample means when you calculated the averages. If n is the number of sample, this
mean that you should divide things by n (and not n-1).
The unit for time related statistics must be in seconds (and not milliseconds).
Let X be something you measure. The standard deviation of X is the square root of the variance
of X. The variance of X is the average of the square of X minus the square of the average of X.
Please note that we must use the "population variance" (and not a "sample variance") in our
calculation since we have all the data points. Let E(X) denote the average of X, you can write:
Var(X) = E(X2 ) - [E(X)]2When you are keep statistics, you should keep a running average.
Please note that it's very important that the event time in the printout is monotonically
increasing (as shown in the sample printout below). This can be difficult to achieve when we
have multiple threads running in parallel. But since we are using only one mutex, you can use the
following simple (although not super-efficient) trick. When you are getting the time for an event,
you must have the mutex locked, and you must not release the mutex until you have printed the
line of printout that corresponds to that event, i.e., reading the clock and printing out the event is
done in one atomic operation.
If the user presses <Ctrl+C> on the keyboard, you must stop the arrival thread and the token
depositing thread, remove all packets in Q1 and Q2, let your server finish transmitting/servicing
the current packet, and output statistics. (Please note that it may not be possible to remove all
packets in Q1 at the instance of signal delivery. The idea here is that once signal delivery has
occurred, the only packet you should serve are the ones currently being transmitted/serviced. All
other packets should be removed from the system.)
You can divide the packets into 3 categories.
- Completed packets: these are the packets that made it all the way to the server and
completed service at the server.
- Dropped packets: these are the packets arrived into the system but never made it even to
Q1 because it needs too many tokens.
- Removed packets: these are the packets that got into Q1 to begin with but never made it
to the server.
All packets should participate in the calculation of the average packet inter-arrival time and
packet drop probability statistics. Only completed packets should participate in the calculation of
the average packet service time statistics. Only completed packets should participate in the
calculation of the average number of packets in Q1/Q2/S1/S2 and time spent in system statistics.
Finally, when no more packet can arrive into the system, you must stop the arrival thread as soon
as possible. Also, when Q1 is empty and no future packet can arrive into Q1, you must stop the
token depositing thread as soon as possible.
Trace Specification File Format
The trace specification file is an ASCII file containing n+1 lines (each line is terminated with a
"\n") where n is the total number of packets to arrive. Line 1 of the file contains a positive integewhich corresponds to the value of n. Line k of the file contains the inter-arrival time in
milliseconds (a positive integer), the number of tokens required (a positive integer), and servicetime in milliseconds (a positive integer) for packet k-1. The 3 fields are separated by space or tabcharacters (or any combination of any number of these characters). There must be no leading or
trailing space or tab characters in a line. If a line is longer than 1,024 characters (including the
'\n' at the end of a line), it is considered an error. A sample tsfile for n=3 packets is provided.
It's content is listed below:
3 (This is the sample tsfile)
2716 2 9253
7721 1 15149
972 3 2614
In the above example, packet 1 is to arrive 2716ms after emulation starts, it needs 2 tokens to beeligible for transmission, and its service time should be 9253ms; the inter-arrival time between
packet 2 and 1 is to be 7721ms, it needs 1 token to be eligible for transmission, and its servicetime should be 15149ms; the inter-arrival time between packet 3 and 2 is to be 972ms, it needs 3token to be eligible for transmission, and its service time should be 2614ms.
In the above example, you should treat these numeric values as "targets" or your emulation. Inyour trace output, you need to print what you measured (i.e., byreading the clock). It should be
very unlikely that a measured inter-arrival time or a measured service time has exactaly the same value as its corresponding target value. For example, the inter-arrival time of packet 3 issuppose to be 972 milliseconds. If the reported actual inter-arrival time between packets 2 and 3
is exactly 972.000 milliseconds, you should look for bugs in your code! Actually, you shouldprobably get a different value every time your rerun your emulation.This file is expected to be error-free. (This means that if you detect a real error in a tsfile, youmust simply print an error message and call exit() immediately. You MUST NOT print
statistics or attempt to recover from error in this case.)
You are expected to create your own tsfile to test your program. Make sure you know how to
create test cases where you know for sure that packets will be wait in Q1, in Q2, or both. You
should be able to look at your tsfile and predict what will happen in the trace and verify that
your program printout is consistent with your prediction.
Minimum Emulation Time
If you have the fastest machine in the universe that there is no overhead anywhere (i.e.,bookkeeping time is zero everywhere, takes zero time to execute any code, etc.) and it's runninga real-time OS that always sleeps exactly the amount of time you ask it to sleep, what would bethe minimum simulation time when you runwarmup2? Of course, this depends on theparameters of your simulation. Let's take the sample tsfile shown above and think about wheneach packet will leave the simulation if we simply run:
./warmup2 -t tsfile.txt
- If there is no overhead anywhere, packet p1 would arrive at exactly 2716ms into thesimulation. At that time, the token bucket should have more than enough tokensfor p1 and p1 would start transmitting immediately. Since the transmission time of p1 is9253ms, p1 should finish transmission at time 11969ms.
- Packet p2 would arrive at exactly 7721ms after the arrival time of packet p1. This meansthat packet p2 would arrive at time 10437ms. At that time, the token bucket should havemore than enough tokens for p2 and p2 would start transmitting immediately. Since thetransmission time of p2 is 15149ms, p2 should finish transmission at time 25586ms.
- Packet p3 would arrive at exactly 972ms after the arrival time of packet p2. This meansthat packet p3 would arrive at time 11409ms. At that time, the token bucket should have more than enough tokens for p3. But, both servers are busy. Therefore, p3 must wait inQ2. The server that transmitted p1 would finish first at time 11969ms and it would start
transmitting p3 as soon as it becomes available. Since the transmission time of p3 is
2614ms, p3 should finish transmission at time 14583ms.From the above analysis, simulation will end when p2 is transmitted at time 25586ms. By doing
analysis like this, you can figure out the minimum simulation time of your program. If yourprogram runs faster than that, you would know for sure that you have a bug in your code! (Ofcourse, if the number of packets is large in an input file, it may not be feasible to do this type of
analysis by hand.)The grading guidelines and grading data (in w2data.tar.gz) have been made available.
Please run the scripts in the guidelines on a standard 32-bit Ubuntu 16.04 system.The grading guidelines is the only grading procedure we will use to grade your program. Noother grading procedure will be used. Please note that the grader may use a different set of trace
files and commandline arguments when grading your submission. (We may make minor
changes if we discover bugs in the script or things that we forgot to test.) It is strongly
recommended that you run your code through the scripts in the grading guidelines.
For your convenience, a copy of the grading scripts are made available here:
section-A.csh
section-B.sh
section-A-all.sh
section-B-all.sh
(Technically speaking, the scripts above are not "grading scripts" since they are just scripts
provided for your convenience to save you some typing. The grader will not run these scripts
when grading.)
After you have download the above shell scripts, please put them in the same directoryas warmup2 and run the following command:
chmod 755 section-*.sh section-*.csh
Please also follow the beginning part of the grading guidelines to unpack the grading data file(i.e., w2data.tar.gz) so that the script can work properly. By the way, please do not run thesegrading scripts in a Ubuntu shared folder. For unknown reasons, running the grading scripts from
within a shared folder may not work correctly!A Perl script, "analyze-trace.txt", is made available to help you to debug your program printout.(I have to name it as if it's a text file. Otherwise, my web server would try to execute the Perl
script.) Please read the comment at the top of the code to see how to use it. This code only worksif your printout is in the right format and each regular packet has 7 lines of printout (with their
timestamps in chronological order) and each dropped packet has 1 line of printout. If your printout has missing lines in the printout or if the lines are in the wrong order, you should fixyour code and rerun this script!For this assignments, please always use pthread_cond_broadcast() to wake up server threads.Please do not use pthread_cond_signal() anywhere in your code. (Yes, this is notthe most efficient way. But since the grader must follow the grading guidelines when grading,this would most likely get you the most number of points.)
In section (A) of the grading guidelines, each test has a minimum emulation time. The numberswere obtained using the Minimum Emulation Time analysis mentionedabove. If the runningtime of your code is too fast or too slow, it means that you have serious bugs in your code andyou need to get them fixed.
标签：Q1,Multi,Bucket,packet,threading,token,ms,time,must From： https://www.cnblogs.com/wx--codinghelp/p/18430528