Parallelism and Speedup in Parallel Computing

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Questions and Answers

What is the maximum speedup that can be achieved when up to 95% parallelism is obtained?

20 (correct)

What is the primary factor that determines the overall performance of a computer system?

Storage performance

Memory performance

Input/Output performance

Processor performance (correct)

What is the formula to calculate the CPU time of a program?

CPU time = # CPU clock cycles for a program × Clock cycle time (correct)

CPU time = Clock rate × # IC

CPU time = Clock period duration × # CPU clock cycles for a program

CPU time = # IC × Clock cycle time

What is the relationship between the problem size and the non-parallelizable fraction (1 - Fe)?

The non-parallelizable fraction decreases with the problem size. Signup and view all the answers

What is the upper bound of Speedup overall reached when p → ∞?

1 / (1 - Fe) Signup and view all the answers

What is the formula to calculate the average number of clock cycles per instruction (CPI)?

CPI = # CPU clock cycles for a program / # IC Signup and view all the answers

What is the significance of the number p = 2048 in the context of parallelization?

It is the number of processors beyond which adding more processors makes no sense. Signup and view all the answers

What is the term used to describe the fraction of a program that can be parallelized?

Fe Signup and view all the answers

What is the primary method to enhance throughput?

Adding extra hardware Signup and view all the answers

What is the relationship between throughput and response time?

As throughput increases, response time increases Signup and view all the answers

What is the most important factor in measuring performance?

Total time of user's tasks completion Signup and view all the answers

How can response time be improved when dealing with high task numbers?

By using parallelization Signup and view all the answers

What is the formula to calculate speedup?

Speedup = ExecutionTime Y / ExecutionTime X Signup and view all the answers

What is the purpose of parallelization in throughput optimization?

To improve the response time Signup and view all the answers

What is the relationship between performance and execution time?

Performance is inversely proportional to execution time Signup and view all the answers

What does the term 'speedup' refer to?

The observed improvement in performance Signup and view all the answers

What is the primary limitation of Amdahl's Law in terms of performance improvement?

The fraction of time that the faster mode can be used Signup and view all the answers

What is the purpose of the speedup enhancement S in Amdahl's Law?

To quantify the performance improvement gained by the enhanced part Signup and view all the answers

What is the relationship between the execution time and the speedup overall in Amdahl's Law?

Speedup overall is the ratio of the old and new execution times Signup and view all the answers

What does the time fraction F represent in Amdahl's Law?

The fraction of time that the faster mode is used Signup and view all the answers

What is the formula for calculating the execution time with enhancement E?

ExecutionTime(E) = ExecutionTime(Old) × (1 - F) + S Signup and view all the answers

What is the purpose of the unenhanced portion Tu in Amdahl's Law demonstration?

To represent the time spent executing the unenhanced part Signup and view all the answers

What is the relationship between the enhanced portion Te and the speedup Se?

Te is equal to the product of Fe and Se Signup and view all the answers

What is the primary goal of throughput optimization in the context of Amdahl's Law?

To minimize the execution time of the system Signup and view all the answers

Study Notes

Speedup and Parallelism

The upper bound of Speedup overall is reached when p → ∞.
Speedup overall is limited by the fraction of parallelism, Fe, and is given by: Speedup overall ≤ 1 / (1 - Fe).
When up to 95% parallelism is obtained, the maximum speedup is approximately 20, which results in approximately p = 2048 processors.

Processor Performance

Processor performance is the most critical component for the whole computer performance.
CPU time is calculated by multiplying the number of CPU clock cycles for a program by the clock cycle time.
CPU time is also given by dividing the number of CPU clock cycles for a program by the clock rate.
The average number of clock cycles per instruction (CPI) is given by the number of CPU clock cycles for a program divided by the instruction count.

Amdahl's Law

Amdahl's Law states that the performance improvement to be obtained from using a given faster mode of execution is limited by the fraction of the time that this faster mode can be used.
The overall performance improvement is given by the execution time without enhancement multiplied by (1 - F) plus the execution time with enhancement divided by S.
The speedup is given by 1 / ((1 - F) + FS).

Amdahl's Law Demonstration

The "unenhanced" portion Tu is given by the time fraction Fe multiplied by the execution time without enhancement.
The "enhanced" portion Te is given by the time fraction Fe multiplied by the execution time without enhancement divided by Se.
The overall speedup is given by the execution time without enhancement divided by the execution time with enhancement.

Increasing the Throughput

Throughput can be enhanced by adding extra hardware, which reduces latency with respect to the load.
Response time is harder to reduce and requires optimization of the architecture or implementing technology.

Performance

The most important factor is the total time of user's tasks completion.
The faster computer is the one that responds to the user in less time.
Response time can be improved through parallelization, especially when the task number is high and intermediate relevant results are produced.

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Description

This quiz assesses understanding of parallelism and speedup in parallel computing, including the upper bound of speedup overall and the relationship between parallelism and maximum speedup.