CISC 372 Exam 1 Final Questions & Answers 2024/2025
15 views 0 purchase
Module
CISC 372
Institution
CISC 372
CISC 372 Exam 1 Final Questions & Answers 2024/2025
How do we write parallel programs? - ANSWERS- move away from single-core systems to multi-core processes
(core = central processing unit, CPU)
- divide the work among the processes/threads
-- try to balance the work so each process has ro...
CISC 372 Exam 1 Final Questions &
Answers 2024/2025
How do we write parallel programs? - ANSWERS- move away from single-core systems to multi-core
processes
(core = central processing unit, CPU)
- divide the work among the processes/threads
-- try to balance the work so each process has roughly the same amount
-- minimize required communication as this is usually a bottleneck & leads to issues
- arrange for a way to synchronize the different processes during both execution & completion
- arrange for communication among processes where necessary to complete work, should be minimized
Task parallelism - ANSWERS- partition various tasks carried out solving the problem among the cores
- Ex.: Questions per TA
Data parallelism - ANSWERS- partition the data used in solving the problem among the cores
- each core carries out similar operations on its part of the data
- Ex.: Exams per TA
Coordination - ANSWERS- cores usually need to coordinate their work
- Communication
- Load balancing
- Synchronization
Communication - ANSWERS- 1+ cores send their current partial sums to another core
Load Balancing - ANSWERS- share the work evenly among the cores so that one is not more heavily
loaded
,Synchronization - ANSWERS- because each core works at its own pace, make sure cores do not get too
far ahead of the rest
C programming: Array Types Declaration - ANSWERS- double a[ ] - unspecified length, incomplete type
- double a[100] - length 100, complete type
C programming: complete type - ANSWERSrequired:
- whenever space must be allocated for the array
- an ordinary (not parameter) declaration of a local/global variable of array type
- element type of an array must be a complete type
C programming: pointers - ANSWERS- memory address of smoe location in memory
- have types which denote the type of object stored at that memory location
- pointer variable contains the memory address of some data that will be interpreted as whatever
declared type
- &, address of - returns the address of that variable
- *, dereference - returns the value stored at that address
C programming: pointers & arrays - ANSWERS- array of arrays (array of pointers)
- one big array (single malloc call)
C programming: pointer arithmetic - ANSWERSif p is a pointer to type T (a complete type) & i is an
integer, then:
- p + i is of type pointer to T
- points to the address that is i T's past p
- sizeof(T) is n bytes, then p + i is i * n bytes after p
,C programming: allocation & deallocation of arrays - ANSWERS- malloc: consumes an argument of type
integer that is the number of bytes to allocate & returns void* pointer that is the address of the first byte
of the block of allocated memory
- int *p = (int*)malloc(10*sizeof(int));, allocates space for 10 ints
- free: consumes void* pointer previously produced by malloc
- can pass in any pointer type, converted automatically
- deallocates the object off of the heap & frees up space
computer architecture basics - ANSWERS- computer CPU cores can only run one program at a time
- modern OSs simulate multiple things running at the same time by scheduling programs & swapping
them in & out of the CPU quickly
- multi-core systems can do more than one thing at a time, but still each program can only run one CPU
at a time
von Neumann architecture - ANSWERSmain memory:
- collection of locations, each which can store both instructions & data
- every location consists of an address, which is used to access the location & contents of the location
central processing unit (CPU):
- control unit: responsible for deciding which instruction in a program should be executed (the boss)
- ALU: responsible for executing the actual instructions (the worker)
Memory -> fetch/read -> CPU -> write/store -> memory - ANSWERSlead to a bottleneck architecture, as
this operation is substantially slower than anything else
caching - ANSWERS- a high-speed data storage layer which stores a subset of data; transient in nature
- extremely fast memory type that acts as a buffer between RAM & CPU; holds frequently requested
data & instructions so that they are immediately available to the CPU when needed
- primary bottleneck: read/fetch, write/store operations to main memory
, - places fast small memory near the CPU & tries to keep the data we will need in there as much as
possible
cache levels - ANSWERS- made up of multiple levels/hierarchy
- very small, very fast caches closer to the CPU (on the chip)
- larger & slower caches above them
- main memory is even larger & slower & secondary storage (i.e. disks) represent the highest level where
things don't fit in memory & can be stored until needed
principle of locality - ANSWERS- accessing one location is usually followed by access to nearby location
- spatial locality: accessing a nearby location
- temporal locality: likely access the same memory again, if it has been accessed recently ; keep accessing
"i" over & over again
cache hit - ANSWERSfind where the data location wanted has been placed in the cache
cache miss - ANSWERSdon't find the data location wanted & must go to main memory to fetch/write it,
usually adding it to the cache due to the principle of locality
mapping (cache) - ANSWERS- how cache is built so that we can find what we are looking for
- directed mapped: each memory location will always go to the same place in the cache, many-to-one
mapping; each cache line has a unique location in the cache to which it will be assigned
- full associative cache: data can be placed anywhere in the cache; a new line can be placed at any
location in the cache
- set associative cache: each data element from memory has some fixed number of possible locations to
be placed in
issues with cache - ANSWERS- when a CPU writes data to cache, the value in cache may be inconsistent
with the value in main memory
- write-through: caches handle this by updating the data in main memory at the time it's written to
cache
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller Bensuda. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for £8.92. You're not tied to anything after your purchase.
