PSTSWM AlphaSC-1000 Point-to-Point Communication Performance

Performance Studies using

PSTSWM

Compaq AlphaServer SC SWAP Performance

(unordered swap of 8KB message using MPI between two nodes)

(performance measured per processor when all processors in node communicating)

< td> Latency Definition:

Date/Person:	January 3, 2002 / P. Worley
Platform:	Compaq AlphaServer SC at Pittsburgh Supercomputer Center (lemieux.psc.edu):
	750 ES45 4-way SMP nodes (1.0 GHz Alpha 21264C with 8MB L2 cache)
Environment:	SC System TS2.5; Digital UNIX V5.1; RMS X.XX
Communication Library:	MPI
SWAP size:	1024 REAL*8 floating point values each direction
Message size:	Largest - 1024 REAL*8 floating point values
	Smallest - 1 REAL*8 floating point values
Processors:	0 and 4 nodes
	1 and 5
	2 and 6
	3 and 7
(T₁₀₂₄-T₅₁₂)/512
Model Error Range:	[1,1024]
Results:

unordered swap using nonblocking send

Data Statistics
bidirectional bandwidth estimated latency model error

(peak MByte/sec) (usec/msg) (max. rel. error)

cache inv. 54.36 31.59 23.2%

1 iter. 55.61 34.30 19.1%

10 iter. 58.77 32.40 16.3%

cache inv. w/overlap 53.47 34.85 18.9%

1 iter. w/overlap 55.13 32.88 20.6%

10 iter. w/overlap 58.71 31.86 29.0%

unordered swap using nonblocking receive

Data Statistics
bidirectional bandwidth estimated latency model error

(peak MByte/sec) (usec/msg) (max. rel. error)

cache inv. 52.28 37.83 22.5%

1 iter. 55.43 36.87 51.6%

10 iter. 59.06 36.89 21.2%

cache inv. w/overlap 54.18 18.71 35.6%

1 iter. w/overlap 57.09 18.80 38.6%

10 iter. w/overlap 59.52 19.56 39.6%

unordered swap using nonblocking send and receive

Data Statistics
bidirectional bandwidth estimated latency model error

(peak MByte/sec) (usec/msg) (max. rel. error)

cache inv. 53.65 41.32 24.5%

1 iter. 56.07 38.23 23.0%

10 iter. 58.17 38.33 24.2%

cache inv. w/overlap 55.73 18.49 33.1%

1 iter. w/overlap 57.37 18.29 29.4%

10 iter. w/overlap 59.21 20.13 30.7%

unordered swap using ready send

Data Statistics
bidirectional bandwidth estimated latency model error

(peak MByte/sec) (usec/msg) (max. rel. error)

cache inv. 48.82 56.05 17.0%

1 iter. 52.92 56.46 20.6%

10 iter. 55.12 56.52 20.8%

cache inv. w/overlap 55.16 18.75 36.0%

1 iter. w/overlap 57.29 18.64 39.5%

10 iter. w/overlap 59.56 19.58 38.6%

unordered swap using nonblocking ready send

Data Statistics
bidirectional bandwidth estimated latency model error

(peak MByte/sec) (usec/msg) (max. rel. error)

cache inv. 50.29 55.57 17.1%

1 iter. 53.02 55.65 19.7%

10 iter. 55.31 56.09 19.8%

cache inv. w/overlap 54.87 18.83 29.9%

1 iter. w/overlap 56.81 18.49 29.4%

10 iter. w/overlap 58.92 19.96 30.6%

native sendrecv

Data Statistics
bidirectional bandwidth estimated latency model error

(peak MByte/sec) (usec/msg) (max. rel. error)

cache inv. 53.26 36.99 20.5%

1 iter. 56.81 36.65 20.0%

10 iter. 59.05 37.80 22.2%

unordered swap using nonblocking sync. send

Data Statistics
bidirectional bandwidth estimated latency model error

(peak MByte/sec) (usec/msg) (max. rel. error)

cache inv. 53.40 33.83 15.7%

1 iter. 55.84 34.32 18.2%

10 iter. 59.33 34.12 17.3%

cache inv. w/overlap 52.18 35.88 24.3%

1 iter. w/overlap 55.24 35.03 18.1%

10 iter. w/overlap 58.42 33.34 13.9%

unordered swap using nonblocking receive with sync. send

Data Statistics
bidirectional bandwidth estimated latency model error

(peak MByte/sec) (usec/msg) (max. rel. error)

cache inv. 53.30 35.26 18.9%

1 iter. 56.03 34.87 18.5%

10 iter. 58.69 34.88 19.1%

cache inv. w/overlap 54.50 35.83 19.1%

1 iter. w/overlap 56.38 37.16 20.9%

10 iter. w/overlap 59.28 38.08 21.0%

unordered swap using nonblocking sync. send and receive

Data Statistics
bidirectional bandwidth estimated latency model error

(peak MByte/sec) (usec/msg) (max. rel. error)

cache inv. 53.51 35.06 15.3%

1 iter. 56.61 34.67 17.9%

10 iter. 58.84 34.71 18.8%

cache inv. w/overlap 55.31 29.58 16.0%

1 iter. w/overlap 57.05 29.83 15.1%

10 iter. w/overlap 59.09 32.91 15.8%

Protocol Sensitivity Summary for Bidirectional Swap of 8192 Bytes (cache inv./no overlap)
Runtime Statistics
Msg Size min Sec min Sec/Msg max MBytes/Sec (mean-min)/min (median-min)/min (max-min)/min

8 3.2607e-02 3.1843e-05 0.50 0.26 0.17 0.76

16 1.6434e-02 3.2097e-05 1.00 0.23 0.11 0.75

32 7.8280e-03 3.0578e-05 2.09 0.30 0.18 0.82

64 4.8000e-03 3.7500e-05 3.41 0.22 0.16 0.63

128 2.5244e-03 3.9444e-05 6.49 0.23 0.11 0.67

256 1.2842e-03 4.0131e-05 12.76 0.39 0.29 0.89

512 9.3380e-04 5.8363e-05 17.55 0.11 0.02 0.43

1024 5.3480e-04 6.6850e-05 30.64 0.10 0.01 0.42

2048 3.7700e-04 9.4250e-05 43.46 0.06 0.01 0.27

4096 3.2500e-04 1.6250e-04 50.41 0.06 0.04 0.19

8192 3.0260e-04 3.0260e-04 54.14 0.03 0.01 0.12

Five Fastest
Protocols

Msg Size 1st 2nd 3rd 4th 5th

8 1 7 9 8 6

16 1 8 7 9 3

32 1 7 9 8 6

64 1 7 8 9 6

128 7 6 1 9 8

256 6 2 7 9 8

512 6 3 2 1 9

1024 7 6 3 2 8

2048 8 1 6 3 2

4096 1 7 6 9 3

8192 6 9 8 2 1

Number of Proctocols With
Runtimes Within X% of Min

Msg Size 1% 5% 25%

8 1 1 7

16 1 1 7

32 1 1 7

64 1 2 7

128 1 1 7

256 1 1 1

512 3 7 7

1024 3 7 7

2048 5 7 7

4096 1 7 9

8192 5 7 9

Protocol Sensitivity Summary for Bidirectional Swap of 8192 Bytes (1 iterations/no overlap)
Runtime Statistics
Msg Size min Sec min Sec/Msg max MBytes/Sec (mean-min)/min (median-min)/min (max-min)/min

8 3.3179e-02 3.2401e-05 0.49 0.24 0.15 0.74

16 1.5620e-02 3.0507e-05 1.05 0.31 0.24 0.84

32 8.1134e-03 3.1693e-05 2.02 0.23 0.10 0.78

64 4.6418e-03 3.6264e-05 3.53 0.26 0.21 0.70

128 1.7520e-03 2.7375e-05 9.35 0.68 0.60 1.34

256 1.4582e-03 4.5569e-05 11.24 0.18 0.12 0.59

512 9.1340e-04 5.7087e-05 17.94 0.10 0.02 0.42

1024 5.1260e-04 6.4075e-05 31.96 0.09 0.01 0.38

2048 3.6200e-04 9.0500e-05 45.26 0.06 0.00 0.27

4096 3.0900e-04 1.5450e-04 53.02 0.04 0.01 0.14

8192 2.8740e-04 2.8740e-04 57.01 0.03 0.01 0.08

Five Fastest
Protocols

Msg Size 1st 2nd 3rd 4th 5th

8 1 7 9 8 6

16 1 7 9 8 2

32 1 3 7 9 2

64 1 7 9 8 2

128 2 1 7 9 8

256 1 7 8 9 3

512 6 8 3 1 7

1024 6 9 7 8 2

2048 3 1 6 9 2

4096 8 9 7 2 3

8192 8 3 2 9 6

Number of Proctocols With
Runtimes Within X% of Min

Msg Size 1% 5% 25%

8 1 1 7

16 1 1 6

32 1 2 7

64 1 1 7

128 1 1 1

256 1 1 7

512 3 7 7

1024 5 7 7

2048 7 7 7

4096 3 7 9

8192 4 7 9

Protocol Sensitivity Summary for Bidirectional Swap of 8192 Bytes (10 iterations/no overlap)
Runtime Statistics
Msg Size min Sec min Sec/Msg max MBytes/Sec (mean-min)/min (median-min)/min (max-min)/min

8 3.2685e-02 3.1919e-05 0.50 0.26 0.17 0.76

16 1.6097e-02 3.1440e-05 1.02 0.27 0.20 0.78

32 8.2033e-03 3.2044e-05 2.00 0.26 0.18 0.75

64 4.6687e-03 3.6474e-05 3.51 0.25 0.21 0.68

128 2.6011e-03 4.0642e-05 6.30 0.21 0.17 0.61

256 1.5521e-03 4.8504e-05 10.56 0.16 0.08 0.53

512 9.1542e-04 5.7214e-05 17.90 0.10 0.01 0.41

1024 4.9844e-04 6.2305e-05 32.87 0.09 0.01 0.41

2048 3.5016e-04 8.7540e-05 46.79 0.07 0.00 0.29

4096 2.9764e-04 1.4882e-04 55.05 0.04 0.01 0.15

8192 2.7690e-04 2.7690e-04 59.17 0.02 0.00 0.07

Five Fastest
Protocols

Msg Size 1st 2nd 3rd 4th 5th

8 1 7 9 8 2

16 1 7 9 8 2

32 1 7 9 8 2

64 1 7 9 8 6

128 1 7 9 8 2

256 1 7 8 9 2

512 9 7 2 8 1

1024 1 8 7 2 6

2048 3 2 6 9 1

4096 3 7 6 9 1

8192 8 7 9 3 6

Number of Proctocols With
Runtimes Within X% of Min

Msg Size 1% 5% 25%

8 1 1 7

16 1 1 7

32 1 1 7

64 1 1 7

128 1 1 7

256 1 3 7

512 7 7 7

1024 7 7 7

2048 7 7 7

4096 7 7 9

8192 7 7 9

Protocol Sensitivity Summary for Bidirectional Swap of 8192 Bytes (cache inv. with overlap)
Runtime Statistics
Msg Size min Sec min Sec/Msg max MBytes/Sec (mean-min)/min (median-min)/min (max-min)/min

8 1.9020e-02 1.8574e-05 0.86 0.48 0.59 1.04

16 9.5506e-03 1.8654e-05 1.72 0.46 0.57 1.03

32 4.7664e-03 1.8619e-05 3.44 0.46 0.59 1.03

64 2.8404e-03 2.2191e-05 5.77 0.43 0.54 1.01

128 1.6390e-03 2.5609e-05 10.00 0.39 0.49 0.80

256 1.0446e-03 3.2644e-05 15.68 0.36 0.42 0.85

512 8.4000e-04 5.2500e-05 19.50 0.10 0.11 0.16

1024 5.1820e-04 6.4775e-05 31.62 0.03 0.02 0.07

2048 3.6060e-04 9.0150e-05 45.44 0.04 0.04 0.09

4096 3.2300e-04 1.6150e-04 50.72 0.02 0.00 0.07

8192 2.9340e-04 2.9340e-04 55.84 0.02 0.01 0.07

Five Fastest
Protocols

Msg Size 1st 2nd 3rd 4th 5th

8 3 5 2 4 9

16 3 5 2 4 9

32 5 3 2 4 9

64 5 3 2 4 9

128 3 5 4 2 9

256 5 4 3 2 9

512 9 5 3 4 2

1024 4 3 9 5 8

2048 3 4 2 8 9

4096 5 3 8 2 9

8192 8 5 2 3 4

Number of Proctocols With
Runtimes Within X% of Min

Msg Size 1% 5% 25%

8 1 4 4

16 2 4 4

32 2 4 4

64 3 4 4

128 2 4 4

256 3 4 4

512 1 3 9

1024 4 7 9

2048 1 6 9

4096 5 8 9

8192 6 8 9

Protocol Sensitivity Summary for Bidirectional Swap of 8192 Bytes (1 iterations with overlap)
Runtime Statistics
Msg Size min Sec min Sec/Msg max MBytes/Sec (mean-min)/min (median-min)/min (max-min)/min

8 1.8847e-02 1.8405e-05 0.87 0.49 0.62 1.07

16 9.4808e-03 1.8517e-05 1.73 0.47 0.61 1.05

32 4.7740e-03 1.8648e-05 3.43 0.46 0.61 1.01

64 2.7894e-03 2.1792e-05 5.87 0.45 0.58 1.01

128 1.6282e-03 2.5441e-05 10.06 0.38 0.52 0.85

256 1.0330e-03 3.2281e-05 15.86 0.27 0.08 0.68

512 8.1960e-04 5.1225e-05 19.99 0.12 0.16 0.24

1024 4.9760e-04 6.2200e-05 32.93 0.05 0.05 0.08

2048 3.6080e-04 9.0200e-05 45.41 0.02 0.02 0.05

4096 3.0940e-04 1.5470e-04 52.95 0.02 0.01 0.05

8192 2.8100e-04 2.8100e-04 58.31 0.02 0.01 0.05

Five Fastest
Protocols

Msg Size 1st 2nd 3rd 4th 5th

8 3 5 4 2 9

16 3 5 2 4 9

32 3 5 2 4 9

64 3 5 4 2 9

128 5 3 4 2 9

256 3 5 2 4 1

512 3 5 9 8 6

1024 9 3 5 2 8

2048 2 9 8 3 5

4096 2 4 8 3 5

8192 5 2 3 4 6

Number of Proctocols With
Runtimes Within X% of Min

Msg Size 1% 5% 25%

8 2 4 4

16 2 4 4

32 2 4 4

64 2 4 4

128 1 4 4

256 2 4 5

512 2 3 9

1024 1 4 9

2048 4 7 9

4096 5 8 9

8192 2 9 9

Protocol Sensitivity Summary for Bidirectional Swap of 8192 Bytes (10 iterations with overlap)
Runtime Statistics
Msg Size min Sec min Sec/Msg max MBytes/Sec (mean-min)/min (median-min)/min (max-min)/min

8 2.0012e-02 1.9543e-05 0.82 0.44 0.62 0.96

16 9.9865e-03 1.9505e-05 1.64 0.44 0.61 0.97

32 5.0171e-03 1.9598e-05 3.27 0.44 0.62 0.96

64 2.9984e-03 2.3425e-05 5.46 0.39 0.56 0.89

128 1.7118e-03 2.6748e-05 9.57 0.34 0.49 0.77

256 1.0776e-03 3.3676e-05 15.20 0.27 0.39 0.60

512 8.6030e-04 5.3769e-05 19.04 0.10 0.11 0.29

1024 5.0510e-04 6.3137e-05 32.44 0.03 0.04 0.06

2048 3.5174e-04 8.7935e-05 46.58 0.02 0.00 0.06

4096 2.9964e-04 1.4982e-04 54.68 0.01 0.00 0.02

8192 2.7492e-04 2.7492e-04 59.60 0.01 0.00 0.02

Five Fastest
Protocols

Msg Size 1st 2nd 3rd 4th 5th

8 4 2 5 3 1

16 4 2 3 5 1

32 2 4 5 3 1

64 2 4 3 5 1

128 2 4 5 3 1

256 2 5 4 3 9

512 5 3 9 7 6

1024 9 5 3 6 7

2048 2 4 9 3 6

4096 3 4 8 2 9

8192 8 2 3 4 9

Number of Proctocols With
Runtimes Within X% of Min

Msg Size 1% 5% 25%

8 2 4 4

16 2 4 4

32 2 4 4

64 4 4 4

128 3 4 4

256 4 4 4

512 3 3 8

1024 1 7 9

2048 7 7 9

4096 7 9 9

8192 6 9 9

DISCUSSION

The AlphaServer SC processing node consists of four processors. In these tests, we examine MPI communication performance between processors in different nodes for communication when all processors in one node are communicating with all processors in the other node. The performance is reported for the processor pair with the maximum execution time, representing the worst case latency and bandwidth that would appear in a highly synchronous communication-intensive operation, such as a collective communication command.