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Concurrency in Milk Management: A Tale of Too Much Milk and Roommates

Dive into a comical and educational journey of roommates, milk shortages, and concurrency issues. Learn how computerized solutions strive to manage milk purchases efficiently. Explore the concept of concurrency through amusing scenarios of excess milk and strategic milk-buying tactics.

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Concurrency in Milk Management: A Tale of Too Much Milk and Roommates

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  1. Too Much Milk Roomate 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

  2. Too Much Milk Roomate ARoomate 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

  3. Computerized Milk Purchase 1 if (milk == 0) { 2if (note == 0) { 3note = 1; 4buy_milk(); 5note = 0; 6} 7 } CS 140 Lecture Notes: Concurrency

  4. Still Too Much Milk Thread A:Thread B: if (milk == 0) { if (note == 0) { if (milk == 0) { if (note == 0) { note = 1; buy_milk(); note = 0; } } note = 1; buy_milk(); note = 0; } } CS 140 Lecture Notes: Concurrency

  5. Thread A: if (note == 0) { if (milk == 0) { buy_milk(); } note = 1; } Thread B: if (note == 1) { if (milk == 0) { buy_milk(); } note = 0; } Second Attempt CS 140 Lecture Notes: Concurrency

  6. Thread A: 1noteA = 1; 2 if (noteB == 0) { 3 if (milk == 0) { 4buy_milk(); 5 } 6 } 7noteA = 0; Thread B: 1noteB = 1; 2 if (noteA == 0) { 3 if (milk == 0) { 4buy_milk(); 5 } 6 } 7noteB = 0; Third Attempt CS 140 Lecture Notes: Concurrency

  7. Thread A: 1noteA = 1; 2 if (noteB == 0) { 3 if (milk == 0) { 4buy_milk(); 5 } 6 } 7noteA = 0; Thread B: 1noteB = 1; 2 while (noteA == 1) { 3// do nothing 4 } 5 if (milk == 0) { 6buy_milk(); 7 } 8noteB = 0; Fourth Attempt CS 140 Lecture Notes: Concurrency

  8. CS 140 Lecture Notes: Concurrency

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