Managing Milk Mishaps: A Concurrency Lesson
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CS 140 Lecture Notes: Concurrency
Slide 1
Too Much Milk
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m
m
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e
A
3
:
0
0
A
r
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h
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:
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m
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3
:
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5
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3
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3
:
1
5
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3
:
2
0
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,
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undefinedCS 140 Lecture Notes: Concurrency
Slide 2
Too Much Milk
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A
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!
CS 140 Lecture Notes: Concurrency
Slide 3
Computerized Milk Purchase
1
if (milk == 0) {2
if (note == 0) {3
note = 1;
4
buy_milk();
5
note = 0;
6
}
7
}
CS 140 Lecture Notes: Concurrency
Slide 4
Still Too Much Milk
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e
a
d
A
:
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r
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a
d
B
:
1
if (milk == 0) {2
if (note == 0) {3
if (milk == 0) {4
if (note == 0) {5
note = 1;
6
buy_milk();
7
note = 0;
8
}
9
}
10
note = 1;
11
buy_milk();
12
note = 0;
13
}
14
}
CS 140 Lecture Notes: Concurrency
Slide 5
Second Attempt
T
h
r
e
a
d
A
:
1
if (note == 0) {2
if (milk == 0) {3
buy_milk();
4
}
5
note = 1;
6
}
T
h
r
e
a
d
B
:
1
if (note == 1) {2
if (milk == 0) {3
buy_milk();
4
}
5
note = 0;
6
}
CS 140 Lecture Notes: Concurrency
Slide 6
Third Attempt
T
h
r
e
a
d
A
:
1
noteA = 1;
2
if (noteB == 0) {3
if (milk == 0) {4
buy_milk();
5
}
6
}
7
noteA = 0;
T
h
r
e
a
d
B
:
1
noteB = 1;
2
if (noteA == 0) {3
if (milk == 0) {4
buy_milk();
5
}
6
}
7
noteB = 0;
CS 140 Lecture Notes: Concurrency
Slide 7
Fourth Attempt
T
h
r
e
a
d
A
:
1
noteA = 1;
2
if (noteB == 0) {3
if (milk == 0) {4
buy_milk();
5
}
6
}
7
noteA = 0;
T
h
r
e
a
d
B
:
1
noteB = 1;
2
while (noteA == 1) {3
// do nothing
4
}
5
if (milk == 0) {6
buy_milk();
7
}
8
noteB = 0;
Learn about the comical scenario of roommates forgetting to buy milk, and delve into concurrency concepts through humorous anecdotes and code snippets. The lecture slides depict the chaotic yet educational journey of handling too much milk through synchronized threads and computerized milk purchases.
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Presentation Transcript
Too Much Milk Roommate A 3:00 Arrive home: no milk 3:05 Leave for store 3:10 Arrive at store 3:15 Leave store 3:20 Arrive home, put milk away CS 140 Lecture Notes: Concurrency Slide 1
Too Much Milk Roommate A Roommate B 3:00 Arrive home: no milk 3:05 Leave for store 3:10 Arrive at store Arrive home: no milk 3:15 Leave store Leave for store 3:20 Arrive home, put milk away Arrive at store 3:25 Leave store 3:30 Arrive home: too much milk! CS 140 Lecture Notes: Concurrency Slide 2
Computerized Milk Purchase 1 if (milk == 0) { 2 if (note == 0) { 3 note = 1; 4 buy_milk(); 5 note = 0; 6 } 7 } CS 140 Lecture Notes: Concurrency Slide 3
Still Too Much Milk Thread A: 1 if (milk == 0) { 2 if (note == 0) { 3 4 5 6 7 8 9 10 note = 1; 11 buy_milk(); 12 note = 0; 13 } 14 } Thread B: if (milk == 0) { if (note == 0) { note = 1; buy_milk(); note = 0; } } CS 140 Lecture Notes: Concurrency Slide 4
Second Attempt Thread A: Thread B: 1 if (note == 0) { 2 if (milk == 0) { 3 buy_milk(); 4 } 5 note = 1; 6 } 1 if (note == 1) { 2 if (milk == 0) { 3 buy_milk(); 4 } 5 note = 0; 6 } CS 140 Lecture Notes: Concurrency Slide 5
Third Attempt Thread A: Thread B: 1 noteA = 1; 2 if (noteB == 0) { 3 if (milk == 0) { 4 buy_milk(); 5 } 6 } 7 noteA = 0; 1 noteB = 1; 2 if (noteA == 0) { 3 if (milk == 0) { 4 buy_milk(); 5 } 6 } 7 noteB = 0; CS 140 Lecture Notes: Concurrency Slide 6
Fourth Attempt Thread A: Thread B: 1 noteA = 1; 2 if (noteB == 0) { 3 if (milk == 0) { 4 buy_milk(); 5 } 6 } 7 noteA = 0; 1 noteB = 1; 2 while (noteA == 1) { 3 // do nothing 4 } 5 if (milk == 0) { 6 buy_milk(); 7 } 8 noteB = 0; CS 140 Lecture Notes: Concurrency Slide 7
