CS470%20Lab%204

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CS470 Lab 4

• TA Notes

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Objective

• Simulate the activities of a producer and
  consumer Page 326
• Use thread synchronization to solve the
  producer-consumer problem Page 329
• You will need to use Full Empty Buffers
• Simulate this with an array of size 25

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Objective cont.

• If the current EMPTY slot is k and producer fills
  it, the the next EMPTY slot will be (k1)N where
  N is the size of the array
• In this simulation the consumer thread is slower
  than the producer thread.
• The producer produces widgets which are
  represented by an ever increasing widget number.

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Objective cont.

• The consumer consumes a widget by replacing it
  with an EMPTY indicator (-1)

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Sample Output

• Producer Produce widget 0 in buffer 0
• 0-1-1-1-1-1-1-1-1-1-1-1-1-1-1-1-1
  -1-1-1-1-1-1-1-1
• Consumer Consumed widget 0 in buffer 0
• -1-1-1-1-1-1-1-1-1-1-1-1-1-1-1-1-1
  -1-1-1-1-1-1-1-1
• Producer Produce widget 1 in buffer 1
• -11-1-1-1-1-1-1-1-1-1-1-1-1-1-1-1
  -1-1-1-1-1-1-1-1
• Consumer Consumed widget 1 in buffer 1
• -1-1-1-1-1-1-1-1-1-1-1-1-1-1-1-1-1
  -1-1-1-1-1-1-1-1
• Producer Produce widget 2 in buffer 2
• -1-12-1-1-1-1-1-1-1-1-1-1-1-1-1-1
  -1-1-1-1-1-1-1-1
• Consumer Consumed widget 2 in buffer 2
• -1-1-1-1-1-1-1-1-1-1-1-1-1-1-1-1-1
  -1-1-1-1-1-1-1-1

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Output cont.

• Producer Produce widget 3 in buffer 3
• -1-1-13-1-1-1-1-1-1-1-1-1-1-1-1-1
  -1-1-1-1-1-1-1-1
• Consumer Consumed widget 3 in buffer 3
• -1-1-1-1-1-1-1-1-1-1-1-1-1-1-1-1-1
  -1-1-1-1-1-1-1-1
• Producer Produce widget 4 in buffer 4
• -1-1-1-14-1-1-1-1-1-1-1-1-1-1-1-1
  -1-1-1-1-1-1-1-1
• Consumer Consumed widget 4 in buffer 4
• -1-1-1-1-1-1-1-1-1-1-1-1-1-1-1-1-1
  -1-1-1-1-1-1-1-1
• Producer Produce widget 5 in buffer 5
• -1-1-1-1-15-1-1-1-1-1-1-1-1-1-1-1
  -1-1-1-1-1-1-1-1
• Producer Produce widget 6 in buffer 6
• -1-1-1-1-156-1-1-1-1-1-1-1-1-1-1-
  1-1-1-1-1-1-1-1
• Consumer Consumed widget 5 in buffer 5
• -1-1-1-1-1-16-1-1-1-1-1-1-1-1-1-1
  -1-1-1-1-1-1-1-1

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Shared Variables

• An integer array (size 25 for our simulation)
• Two other fields nextEmpty(initial0) and
  nextFull(initial0)
• Three handles for the synchronization objects
  full, empty, and mutex
• Keep a running flag as in Project 2

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CS 470Lab 4

• Program Layout

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Overall Layout

• Producer Function
• Consumer Function
• Driver (main)

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Producer

• Say that its running
• Initialize Widget Number
•  
• While(runFlag)
• Simulate producing by sleeping a random time
  (0..200)
• And incrementing the widget number
• P(empty) /If there is an empty spot we can add
  to the buffer/
• P(mutex) /If the consumer is not in its
  critical section the producer can be in the
  critical section/
• Store the widget number in the next available
  empty slot
• Say what you did
• Say what the buffer looks like (show the buffer)
• Update the next available empty position
• V(mutex) /Exit critical section/
• V(full) /Make sure to let the consumer know
  there is at least one widget/
•  
• Say terminating
• Return (DWORD) 0

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Consumer

• Say running
•  
• While(runFlag)
• P(full) /If there is a Widget we (consumer)
  can go, wait otherwise/
• P(mutex) / If the producer is not in its
  critical section we can go/
• Get the widget number in the next available full
  slot,
• And store an empty holder (-1) there
• Say what you did
• Say what the buffer looks like (show the buffer)
• Update the next available full position
• V(mutex) /Exit our critical section /
• V(empty) / Let the producer know there is an
  open spot for a widget /
• Simulate consuming by sleeping a random time
  (0..300)
•  
• Say terminating
• Return (DWORD) 0

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Driver

• Driver
•  
• Error check input argc (the number of parameters)
• Create synchronization objects(mutex as a
  MutexObject, full and empty as SemaphoreObjects)
• Initialize the buffer record so that nextFull 0
  nextEmpty 0,
• And all array positions represent empty(-1)
• Generate the producer thread
• Generate the consumer thread
• Generate and set a waitable timer
• Wait for the timers signal
• Change the keep running signal to FALSE
• Wait for thread objects to terminate
• Clean up by closing handles
• Say done

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2006 addition

• Program 4 Create a program that has two threads,
  one that fills a buffer and another that empties
  it. The rate at which the buffer is filled and
  emptied is variable. In doing this, one thread
  might have to wait for the other to process the
  buffer to continue.
• General program comments
• Define handles globally, there should be a mutex,
  full, empty, and one for each thread.
• Define a producer and consumer sleep time, or use
  random times. Up to you.
• Producer and consumer methods should be defined
  as
• DWORD WINAPI producer( LPVOID )
• DWORD WINAPI consumer( LPVOID )
• Main pseudo-code
• initialize variables, widgets, random number
  generator
• error check run time input
• create semaphores and mutex
• set the timer
• say running
• create consumer and producer threads
• wait until timer is done
• say finishing, set run flag to false
• close handles

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2006 addition

• Producer pseudo-code
• say running
• initialize widget number
• while run flag
• sleep for sleep time or random time
• wait for empty and mutex
• store widget in empty slot
• say what the buffer looks like
• update next available widget position
• release mutex and full
• say terminating

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2006 addition

• Consumer pseudo-code
• say running
• while run flag
• wait for full and mutex
• say what you did
• get widget number from next available full
  slot, store -1 there
• say what buffer looks like
• update next available full position
• release mutex and empty
• sleep for sleep time or random time
• say terminating
• Here are the msdn links for using semaphores and
  mutex objects
• http//msdn.microsoft.com/library/en-us/dllproc/ba
  se/using_semaphore_objects.asp
• http//msdn.microsoft.com/library/en-us/dllproc/ba
  se/using_mutex_objects.asp