Homework 3:

OpenMP and

Performance Evaluation

1) Parallelize the following piece of code in OpenMP (pencil and paper):

READ *,n

w = 1/n

sum = 0

DO i=1,n

x = w * (i-0.5)

sum = sum + 4/(1+x*x)

ENDDO

1) Parallelize the following piece of code in OpenMP (pencil and paper):

READ *,n

w = 1/n

sum = 0

!$OMP PARALLEL DO (private(x), shared(w),reduction(+:sum))

DO i=1,n

x = w * (i-0.5)

sum = sum + 4/(1+x*x)

ENDDO

!$OMP END PARALLEL DO

2) Performance Evaluation - Mean Values

• The following table shows the results of 3 different benchmarks on 3 different systems:

• System Code 1 Code 2 Code 3A 1 1 40 B 2 2 30C 4 4 4

• By using different mean values show that:

• a) System A is best

• b) System B is best

• c) System C is best

2) Performance Evaluation - Mean Values

• The following table shows the results of 3 different benchmarks on 3 different systems:

• System Code 1 Code 2 Code 3 arith harm geom A 1 1 40 14.0 1.5 3.4 B 2 2 30 11.3 2.9 4.9C 4 4 4 4.0 4.0 4.0

• By using different mean values show that:

• a) System A is best - arithmetic mean.

• b) System B is best - geometric mean.

• c) System C is best - harmonic mean.

3) Performance Evaluation - Regression

• The following table shows the results of a communication benchmark for different message length:

• Prepare and analyse the data and discuss:– a) Is linear regression appropriate to analyse

these results?

– b) Calculate slope and intersection for a linear regression (and R2 - if you like).

Length Time [s]10 1.95E-05 40 2.15E-05 50 1.91E-05 70 9.24E-05 80 2.51E-05 100 2.27E-05 200 2.79E-05 400 3.23E-05 600 3.67E-05 1000 4.03E-05 2000 5.99E-05 5000 1.08E-04 10000 2.37E-04

3) Performance Evaluation - Regression

• The following table shows the results of a communication benchmark for different message length:

• Prepare and analyse the data and discuss:– a) Is linear regression appropriate to analyse

these results?

• Yes - based on graph (next slide)– b) Calculate slope and intersection for a

linear regression (and R2 - if you like).

• Intersection: 2.04 E-5

• Slope: 2.08 E-8

• R2: 0.9906

Length Time [s]10 1.95E-05 40 2.15E-05 50 1.91E-05 70 9.24E-05 80 2.51E-05 100 2.27E-05 200 2.79E-05 400 3.23E-05 600 3.67E-05 1000 4.03E-05 2000 5.99E-05 5000 1.08E-04 10000 2.37E-04

3) Performance Evaluation - Regression

All points: y = 1.98E-08x + 2.73E-05

R2 = 8.90E-01

No Outlier: y = 2.08E-08x + 2.03E-05

R2 = 9.91E-01

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