Shared memory is physically sharing some memory location, while message passing just passes information directly from one thread to another.
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What is a synchronised operation?
Both input and output channels have to be ready before anything else executes
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What is an asynchronous operation?
Finished processes placed into a buffer, so threads don't have to wait.
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What's the difference between streaming and transactions?
Streamed data goes into a buffer on the receiving end, while transactions are sent asynchronously with the beginning and end synchronised.
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When writing a channel communication a:>b, which of a and b are the channel and the data? Is this operation input or output?
a is the channel, while data is on the right. This is b receiving data from channel a.
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What does a replicated par block do?
Works like a for loop, allows iterations over a number of channels and concurrent processes.
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What is deadlock?
The program gets stuck because two processes are waiting for some information and blocking each other, making the program halt.
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What is livelock?
Program is running without making any progress.
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Define CSP.
Communicating sequential processes - a theoretical language used to model concurrent systems.
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What does α(P) define?
The alphabet of events in process P
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What does SKIP mean?
Successful termination of a process
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What does STOP mean?
Deadlock
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What is P;Q, when P and Q are two processes?
Sequential composition, P followed by Q
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What is a->P?
Prefixing, a then P
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What is x : A -> P(x)?
Menu choice
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What is a traces set?
A list of all possible traces of a process
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What does "P trace refines Q" mean?
All of Q's traces are contained in P
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What is Bernstein's criteria for task independency?
Tasks T1 and T2 must not feed each other data and their outputs must not overlap.
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What is a transition diagram?
Basically a finite state machine - draws out the many states and links them visually.
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# = ?
3 -# signifies the number of elements in the trace
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What is the difference between explicit external and internal choices?
External choice symbol is a square, internal is missing the bottom edge. Internal choice is non-deterministic, but otherwise both are the same as | for the most part
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What is a failure set made up of?
The union of all of the refusal sets.
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What are the entries in Flynn's taxonomy?
SISD, SIMD, MISD, MIMD
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What does MISD stand for?
Many instructions, single dataset.
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What does SIMD stand for?
Single instruction, many datasets.
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How does geometric parallelism work?
Quasi-independent but identical processes operate on a portion of data and interact only with neighbours.
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How does process farming work?
Source distributes to many workers, and the workers independently process the data and send the result back to the farmer.
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How does algorithmic parallelism work?
Processes vary across threads, the algorithm itself is split into sections that can be executed concurrently.
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What is static load balancing?
Programmer assigns each thread a fixed amount of work, which works well for homogeneous multicore systems.
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What is dynamic load balancing?
When a process is complete, it takes some of the load from the heaviest remaining process. Ideal when workload is uneven across processes.
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What is Amdahl's law?
The speedup gained by using many processes in parallel is limited by the time needed for each sequential fraction.
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What is the first condition for deadlock?
Mutual exclusion
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What is the second condition for deadlock?
Wait for
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What is the third condition for deadlock?
No preemption
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What is the fourth condition for deadlock?
Circular wait
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Other cards in this set
Card 2
Front
What is a synchronised operation?
Back
Both input and output channels have to be ready before anything else executes
Card 3
Front
What is an asynchronous operation?
Back
Card 4
Front
What's the difference between streaming and transactions?
Back
Card 5
Front
When writing a channel communication a:>b, which of a and b are the channel and the data? Is this operation input or output?
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