DS 642: Applications of Parallel Computing Lecture 4 Quiz

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Questions and Answers

What is the computational intensity in the context of matrix multiplication?

  • O(n^2)
  • O(M_{fast})
  • O((M_{fast})^{1/2}) (correct)
  • O(n^3)

Which data layout works well for any cache size but incurs expensive index calculations to find A[i,j]?

  • Recursive layout
  • Z-Morton order (correct)
  • Col/Row Major
  • Blocked-Row Major

According to Hong & Kung's theorem, what is the relationship between the number of words moved between fast and slow memory and the computational intensity?

  • #words moved = O(n^2)
  • #words moved = Ω (n^3)
  • #words moved = O(n)
  • #words moved = O( (n^3) / (M_{fast})^{1/2} ) (correct)

In recursive matrix multiplication, at what point should recursion be cut off?

<p>1x1 (D)</p> Signup and view all the answers

Which matrix order works well for any cache size but incurs expensive index calculations?

<p>Hilbert curve order (A)</p> Signup and view all the answers

What is the key focus of optimizing latency and bandwidth in parallel matrix multiplication according to the lecture?

<p>Reducing communication overhead (C)</p> Signup and view all the answers

What is the key factor in determining the minimum possible time for a computation in a machine with fast and slow memory levels?

<p>Number of memory elements moved between fast and slow memory (B)</p> Signup and view all the answers

In the context of matrix multiplication, what does 'CI' stand for?

<p>Computational Intensity (C)</p> Signup and view all the answers

How many arithmetic operations are involved in the recursive matrix multiplication function RMM when n = 1?

<p>$1$ (A)</p> Signup and view all the answers

What is the primary purpose of defining the function C = RMM(A, B, n) recursively in matrix multiplication?

<p>To break down large matrix multiplications into smaller, more manageable sub-multiplications (D)</p> Signup and view all the answers

In the context of matrix multiplication, what does 'tm' represent in the machine balance equation?

<p>Time per slow memory operation (B)</p> Signup and view all the answers

Which factor directly influences the balance of a computation in terms of memory movement between fast and slow memory levels?

<h1>memory elements moved between fast and slow memory (B)</h1> Signup and view all the answers

What is the significance of the 'Newer Record' of 2.3729269?

<p>It represents a reduction in the number of arithmetic operations needed for matrix multiplication. (C)</p> Signup and view all the answers

Why is it mentioned that fast methods, besides Strassen's algorithm, may require unrealistically large n?

<p>To suggest the need for further research in reducing data movement in matrix operations. (B)</p> Signup and view all the answers

What does the term 'Computational Intensity' refer to in the context of matrix operations?

<p>The ratio of computational work to data movement in matrix calculations. (D)</p> Signup and view all the answers

Why is it important to extend the lower bound on the number of words moved in certain algorithms?

<p>To improve the stability and efficiency of numerical calculations. (C)</p> Signup and view all the answers

In matrix multiplication, what does 'BLAS1' refer to?

<p>Matrix-vector operations involving dot product, saxpy, etc. (B)</p> Signup and view all the answers

What role do vendors and others play in optimizing Basic Linear Algebra Subroutines (BLAS)?

<p>Supplying optimized implementations of industry standard interfaces for matrix calculations. (D)</p> Signup and view all the answers

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