Class Climate Surveys and Course Overview

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Today

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Class Climate Surveys

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All quizzes & exams from this quarter:

SE-2811

Slide design: Dr. Mark L. Hornick

Content: Dr. Hornick

Errors: Dr. Yoder

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Overview of course



Muddiest Point of the quarter



Practice Exercises from quarter



TBA?: Graphical Overview of course



TBA?: Review material for multithreading

based on my review of your final projects

SE-2811

Dr.Yoder

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Embedded Systems

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Terminology



Electronics and Interfacing



Low-level I/O (simple digital input and output)



Real-Time Systems



Terminology



Meeting deadlines



Predicting and measuring latency



Predicting bandwidth, both analog and digital



Scheduling, especially RMA



Multithreading

SE-2811

Dr.Yoder

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It’s got to be fast… or does it?

SE-2811

Dr.Yoder

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Select all that are real-time systems

a.

Video Game

b.

Aircraft Autopilot

c.

Refinery Process Control

d.

Cash Register

e.

Smartphone

SE-3910  - Dr. Josiah Yoder

Slide style: Dr. Hornick

Much Material: Dr. Schilling

5

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Select all that are embedded systems

a.

Video Game

b.

Aircraft Autopilot

c.

Refinery Process Control

d.

Cash Register

e.

Smartphone

SE-3910  - Dr. Josiah Yoder

Slide style: Dr. Hornick

Much Material: Dr. Schilling

6

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What fun to wire and smoke…

SE-2811

Dr.Yoder

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SE-3910  - Dr. Josiah Yoder

Slide style: Dr. Hornick

Much Material: Dr. Schilling

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SE-3910  - Dr. Josiah Yoder

Slide style: Dr. Hornick

Much Material: Dr. Schilling

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11

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13

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Considering any one of the resistors on the

previous slides, is it large enough to not

damage a GPIO pin configured as output, if the

resistor ties the output to ground?



Sourcing limit: 4mA



Sinking limit: 8mA



Voltage: 3.3 V

SE-2811

Dr.Yoder

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3

.

3

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?



Sourcing limit: 4mA



Sinking limit: 8mA



Voltage: 3.3 V

SE-2811

Dr.Yoder

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SE-3910  - Dr. Josiah Yoder

Slide style: Dr. Hornick

Much Material: Dr. Schilling

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1



If S1 is closed, and

S2 is opened, what is

the voltage across

C1?



If S2 is closed, and

S1 is opened?



I

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I

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?

SE-2811

Dr.Yoder

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

If S1 is open and S2

is closed, compute

the voltage from

GPIO 12 to ground.



(Assume GPIO 12 is

not connected to

anything)

SE-2811

Dr. Yoder

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SE-3910  - Dr. Josiah Yoder

Slide style: Dr. Hornick

Much Material: Dr. Schilling

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(

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)

SE-3910

Dr.Yoder

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

Voltage from

GPIO to ground

if



S1 is closed



S2 is closed



Both are open



Current from

source if both

are closed

SE-2811

Dr.Yoder

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

Suppose L1 is a

diode with 

V

d

 = 1.8 

V



Ex: Write a formula

relating the current

through L1 to R1.



Ex: Solve for R1 if we

want the (max)

current to be 10 mA.

SE-2811

Dr.Yoder

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It’s like Java, only with pointers…

SE-2811

Dr Yoder

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

Why  does this

6

unsigned short *pt;

7

pt = myArray[0];



Produce this?

myLib.c:7: error: data definition has no type or storage class

myLib.c:7: error: type defaults to 'int' in declaration of 'pt'

myLib.c:7: error: conflicting types for 'pt'

myLib.c:6: note: previous declaration of 'pt' was here

myLib.c:7: error: initialization makes integer from pointer without a cast



How should it be written?



Are these compile or link errors?

http://stackoverflow.com/questions/6639256/poi

nter-to-first-element-in-array-c

SE-2811

Dr Yoder

24

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void foo(struct bar2* b);

…

struct bar b;

And then….



foo((struct bar2*) b*)



foo((bar2*) *b)



foo((bar2*) b&)



foo((struct bar2*) &b)

SE-3910  - Dr. Josiah Yoder

Slide style: Dr. Hornick

Much Material: Dr. Schilling

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How do you get a reference (pointer) to the first

element in an array?

int x[5] = {1,2,3,4,5}

boolean foo(int *ip);

a)

foo(&x);

b)

foo(&x[0]);

c)

foo(x);

d)

foo(x[0]);

SE-3910  - Dr. Josiah Yoder

Slide style: Dr. Hornick

Much Material: Dr. Schilling

26

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int x[5] = {1,2,3,4,5}

boolean foo(int *ip);

a)

foo(&x+1);

b)

foo(&x[0]);

c)

foo(x+1);

d)

foo(x[0]);

e)

foo(&(x+1));

SE-3910  - Dr. Josiah Yoder

Slide style: Dr. Hornick

Much Material: Dr. Schilling

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Why do we have both .h and .cpp file

extensions for C++?  Why not just have .cpp

(like .java for Java classes)?

Answer these questions:

1.

What should you put into a class’s .h file?

2.

What should you put into a class’s .cpp file?

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SE-2811

Dr.Yoder

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[

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]



syntax error



warning: implicit declaration of function `...'



point.m:40: error: ‘mypoint’ undeclared (first use in

this function)



parse error before `...‘



collect2: ld returned 1 exit status



undefined reference to `filterText'



/usr/lib/crt1.o(.text+0x18): undefined reference to

`main '

SE-2811

Dr.Yoder

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

syntax error



point.m:40: error: ‘mypoint’ undeclared (first use in

this function)



collect2: ld returned 1 exit status



/usr/lib/crt1.o(.text+0x18): undefined reference to

`main '



parse error before `...‘



undefined reference to `filterText'



warning: implicit declaration of function `...'

SE-2811

Dr.Yoder

30

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

Creating a signal from sine waves



Frequency content of a signal



Analog bandwidth



Stroboscopic effect



Why some cables can carry more data than

others



Even more outcomes on outcomes page, if

desired

SE-2811

Dr.Yoder

31

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Wiggly and squiggly…

SE-2811

Dr.Yoder

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SE-3910  - Dr. Josiah Yoder

Slide style: Dr. Hornick

Much Material: Dr. Schilling

33

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SE-3910  - Dr. Josiah Yoder

Slide style: Dr. Hornick

Much Material: Dr. Schilling

34

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SE-3910  - Dr. Josiah Yoder

Slide style: Dr. Hornick

Much Material: Dr. Schilling

35

0

1 Volt/div

1 ms/div

D

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[Witty saying needed…]

SE-2811

Dr.Yoder

36



TODO: Get all the noisy-analog-channel

data-rates

SE-2811

Dr Yoder

37

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P   = 1,000,0000,000,000,000



T   = 1,000,000,000,000



G   = 1,000,000,000



M  = 1,000,000



K   =  1,000



()   =  1



m = 1/1,000



us = 1/1,000,000



ns = 1/1,000,000,000  (us = 

μ

s)

SE-3910  - Dr. Josiah Yoder

Slide style: Dr. Hornick

Much Material: Dr. Schilling

38

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

Pi   = 1024

5



Ti   = 1024

4



Gi   = 1024

3



Mi  = 1024

2



Ki   =  1,024



()   =  1

SE-3910  - Dr. Josiah Yoder

Slide style: Dr. Hornick

Much Material: Dr. Schilling

39

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

How many SI Kb is 4 Gibibytes (GiB)?



N

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!

SE-2811

Dr.Yoder

40

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

Suppose you are designing a real-time

system, and the “remote display” design team

says they can handle a data rate of 100MB/s

according to their current design.



What should you ask?

SE-2811

Dr. Yoder

41

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SE-3910  - Dr. Josiah Yoder

Slide style: Dr. Hornick

Much Material: Dr. Schilling

42

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

Suppose an audio signal has a maximum

frequency of 60 KHz (SI).



What is the minimum sampling rate needed to

reconstruct this signal completely?



What bit-rate is needed if each sample has

65,536 possible values? (Use a binary multiplier)

SE-2811

Dr.Yoder

43

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

With 1 KB buffer, there will be ____ samples

per buffer.



With a 40KHz sampling rate, the buffer must

be filled every ____ milliseconds (audio

deadline)



With 40KHz sampling, the maximum

frequency sine-wave that can be encoded

is…

[HINT: To compute:   buffer size / sample size

= samples per buffer

Similarly, samples per buffer / sample rate =

time to empty buffer]

SE-2811

Dr.Yoder

44

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

TODO: Various unit analyses (e.g. audio

rates, video rates, Nyquist theorem)

SE-2811

Dr.Yoder

45

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When will I ever get all this done?

SE-2811

Dr.Yoder

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SE-3910  - Dr. Josiah Yoder

Slide style: Dr. Hornick

Much Material: Dr. Schilling

47

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

Does this meet the theoretical 69% bound?



Is it guaranteed to succeed?



Is it guaranteed to fail?



What simplifying assumptions do we make in

RMA scheduling?



Round-robin vs. Cyclic Code Scheduling

SE-2811

Dr Yoder

48

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Two hands, twice the productivity…

SE-2811

Dr.Yoder

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…

.

(

c

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)

"

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"

I was blank and interviewer was short of time

and eventually he couldnt explain the reason to

me.

http://stackoverflow.com/questions/5269535/jav

a-threads-vs-pthreads

SE-3910  - Dr. Josiah Yoder

Slide style: Dr. Hornick

Much Material: Dr. Schilling

50

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:

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.

Consider this code-

snippet

Queue q = …

…

synchronized(q) {

   while(true) {

     img = getImage();

     q.offer(img);

   }

}

// on another thread

synchronized(q) {

   while(true) {

      img = q.poll();

      showImage();

   }

}

SE-2811

Dr.Yoder

51

E

x

:

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Consider this code-

snippet

Queue q = …

…

synchronized(q) {

i

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=

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(

)

;

   while(true) {

      q.offer(img);

   }

}

// on another thread

synchronized(q) {

   while(true) {

      img = q.poll();

   }

s

h

o

w

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m

a

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e

(

)

;

}

SE-2811

Dr.Yoder

52

C

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x

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m

p

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.

E

x

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:



Both the Java and Qt solutions will behave

poorly if I start multiple threads.



P

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:



Click start



Click start



// what happens? (For Java? For Qt?)



Click stop



// what happens? (For Java? For Qt?)

SE-2811

Dr.Yoder

53

M

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Q

t



Why is it necessary to include a fifth

argument when connecting the “stop” button

to the “interrupt” socket on the prime worker

thread?

SE-2811

Dr.Yoder

54

S

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y



What are the two major things that a compiler

does that invalidate the sequential

consistency memory model?



Why does it do these things?

SE-2811

Dr Yoder

55

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.

SE-2811

Dr.Yoder

56

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)



Explain the advantage of the

ConcurrentSkipListMap over a TreeMap that

has been synchronized with

Collections.synchronizedMap(Map<K,V> m)

SE-2811

Dr.Yoder

57

“

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”

void publishMessage() {

    answer = 42;

    isReady = 1;

}

void consumeMessage() {

    if (isReady)

sout

("%d\n", answer);

}

http://preshing.com/2013070

2/the-happens-before-

relation/

Exercise:

How might this code

execute to print 

0

instead of 

42

?

(You may use

reordering and/or

caching in your solution)

SE-2811

Dr.Yoder

58

E

x

.

public void a() {

   System.out.println(“x”);

   System.out.println(“y”);

}

public void b() {

   System.out.println(“x”);

   System.out.println(“y”);

}

SE-2811

Dr.Yoder

59

Prove the following code is(n’t) free of data races:

E

x

.

public void a() {

   x = 5;

   System.out.println(“x”);

}

public void a() {

   x = 5;

  System.out.println(“x”);

}

SE-2811

Dr.Yoder

60

Prove the following code is(n’t) free of data races:

E

x

.

public void a() {

  synchronized {

    x = 5;

    System.out.println(“x”);

  }

}

SE-2811

Dr.Yoder

61

Prove the following code is(n’t) free of data races:

E

x

.

if(theLogger==null){

  synchronized (EventLogger.class){

    if(theLogger == null){

       theLogger = new EventLogger(path);

    }

  }

}

SE-2811

Dr.Yoder

62

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.

if(theLogger==null){

  synchronized (EventLogger.class){

    if(theLogger == null){

       theLogger = new EventLogger(path);

    }

  }

}

SE-2811

Dr.Yoder

63

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Loggers is a map.

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if(loggers.get(path)==null){

  synchronized (loggers){

    if(loggers.get(path) == null){

      EventLogger n = new EventLogger(path);

    }

  }

}

SE-2811

Dr.Yoder

64

E

x

.

if(loggers.get(path)==null){

  synchronized (loggers){

    if(loggers.get(path) == null){

       Logger logger = new EventLogger(path);

       loggers.put(path, logger);

    }

  }

}

SE-2811

Dr.Yoder

65

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if(loggers.get(path)==null){

  synchronized (loggers){

    if(loggers.get(path) == null){

       Logger logger = new EventLogger(path);

       loggers.put(path, logger);

    }

  }

}

SE-2811

Dr.Yoder

66

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?

synchronized(this) {

    im = getImage();

    q.put(im);

}

synchronized(this) {

    im = q.get(im);

    display(im);

}

SE-2811

Dr.Yoder

67

E

T

H

I

C

S

But that’s not all, there’s more!

SE-2811

Dr.Yoder

68

C

a

s

e

S

t

u

d

i

e

s



What do you do if you are on a project that

puts human lives at risk and things are going

poorly?



What can we learn from Appollo 1, 11, and

Toyota?

SE-2811

Dr Yoder

69