PSTSWM AlphaSC-667 Point-to-Point Communication Performance

Performance Studies using

PSTSWM

Compaq AlphaServer SC SWAP Performance

(unordered swap of 128KB message using MPI within a node)

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

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Date/Person:	July 17, 2000 / P. Worley
Platform:	Compaq AlphaServer SC at Oak Ridge National Laboratory (falcon.ccs.ornl.gov):
	64 ES40 4-way SMP nodes (667 MHz Alpha 21264a with 8MB L2 cache)
Environment:	SC System v1.0; Digital UNIX V5.0; RMS 2.37
Communication Library:	MPI
SWAP size:	16384 REAL*8 floating point values each direction
Message size:	Largest - 16384 REAL*8 floating point values
	Smallest - 16 REAL*8 floating point values
Processors:	0 and 1
	2 and 3
Latency Definition:	(T₁₀₂₄-T₅₁₂)/512
Model Error Range:	[1,1024]
Results:

unordered simple swap

Data Statistics
bidirectional bandwidth estimated latency model error

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

cache inv. 175.65 36.05 55.7%

1 iter. 91.43 36.68 87.5%

10 iter. 333.49 36.97 58.1%

unordered swap using nonblocking send

Data Statistics
bidirectional bandwidth estimated latency model error

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

cache inv. 215.15 43.67 49.7%

1 iter. 406.93 43.62 51.5%

10 iter. 413.87 41.84 53.5%

cache inv. w/overlap 215.01 47.56 45.1%

1 iter. w/overlap 421.72 48.51 46.4%

10 iter. w/overlap 409.59 38.90 56.5%

unordered swap using nonblocking receive

Data Statistics
bidirectional bandwidth estimated latency model error

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

cache inv. 241.43 33.54 58.5%

1 iter. 422.95 32.85 60.9%

10 iter. 426.07 35.45 58.4%

cache inv. w/overlap 244.40 22.78 66.3%

1 iter. w/overlap 387.67 23.38 66.9%

10 iter. w/overlap 449.75 26.84 65.5%

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. 239.10 31.62 60.6%

1 iter. 406.68 27.97 66.1%

10 iter. 433.58 31.32 62.6%

cache inv. w/overlap 244.63 23.31 65.8%

1 iter. w/overlap 391.38 22.92 68.1%

10 iter. w/overlap 446.28 25.28 68.0%

unordered swap using ready send

Data Statistics
bidirectional bandwidth estimated latency model error

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

cache inv. 231.74 68.64 36.9%

1 iter. 382.80 70.48 36.5%

10 iter. 426.31 69.51 38.1%

cache inv. w/overlap 243.27 22.96 66.4%

1 iter. w/overlap 431.87 23.25 67.3%

10 iter. w/overlap 450.00 25.80 66.8%

unordered swap using nonblocking ready send

Data Statistics
bidirectional bandwidth estimated latency model error

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

cache inv. 234.22 69.21 36.4%

1 iter. 408.58 69.45 37.8%

10 iter. 418.36 69.83 37.4%

cache inv. w/overlap 243.49 23.50 65.3%

1 iter. w/overlap 436.32 23.15 67.5%

10 iter. w/overlap 444.54 25.23 67.8%

native sendrecv

Data Statistics
bidirectional bandwidth estimated latency model error

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

cache inv. 243.63 32.21 59.8%

1 iter. 411.92 32.10 61.9%

10 iter. 419.58 33.18 60.4%

unordered swap using nonblocking sync. send

Data Statistics
bidirectional bandwidth estimated latency model error

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

cache inv. 213.26 37.19 56.0%

1 iter. 404.17 36.98 58.4%

10 iter. 422.68 36.79 58.7%

cache inv. w/overlap 235.61 59.87 53.7%

1 iter. w/overlap 337.81 59.45 54.8%

10 iter. w/overlap 412.46 45.79 64.7%

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. 240.32 37.10 56.7%

1 iter. 402.56 37.34 58.6%

10 iter. 417.45 36.95 59.0%

cache inv. w/overlap 245.32 37.44 56.6%

1 iter. w/overlap 354.25 36.75 58.3%

10 iter. w/overlap 419.22 38.78 58.1%

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. 238.10 38.23 55.6%

1 iter. 399.49 38.20 58.0%

10 iter. 415.85 38.34 57.7%

cache inv. w/overlap 242.23 33.07 59.1%

1 iter. w/overlap 428.34 32.74 61.2%

10 iter. w/overlap 449.22 34.30 60.9%

Protocol Sensitivity Summary for Bidirectional Swap of 131072 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

128 3.7664e-02 3.6782e-05 6.96 0.30 0.21 0.95

256 2.1170e-02 4.1348e-05 12.38 0.29 0.26 0.80

512 2.3163e-02 9.0480e-05 11.32 0.08 0.06 0.28

1024 1.1737e-02 9.1695e-05 22.33 0.09 0.05 0.28

2048 5.6282e-03 8.7941e-05 46.58 0.12 0.09 0.39

4096 2.8596e-03 8.9362e-05 91.67 0.14 0.10 0.43

8192 1.6846e-03 1.0529e-04 155.61 0.09 0.06 0.21

16384 1.3380e-03 1.6725e-04 195.92 0.07 0.07 0.21

32768 1.1922e-03 2.9805e-04 219.88 0.10 0.11 0.25

65536 1.1162e-03 5.5810e-04 234.85 0.10 0.09 0.39

131072 1.0760e-03 1.0760e-03 243.63 0.08 0.04 0.39

Five Fastest
Protocols

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

128 6 3 2 0 7

256 6 2 3 0 7

512 6 3 2 0 7

1024 6 2 3 8 0

2048 6 3 2 0 8

4096 6 3 2 1 8

8192 6 2 9 1 3

16384 2 3 8 6 9

32768 6 9 3 8 2

65536 6 2 8 9 3

131072 6 2 8 3 9

Number of Proctocols With
Runtimes Within X% of Min

Msg Size 1% 5% 25%

128 1 3 7

256 2 3 5

512 3 4 8

1024 1 6 8

2048 3 4 8

4096 1 4 8

8192 1 4 10

16384 3 5 10

32768 3 4 9

65536 1 5 9

131072 2 6 9

Protocol Sensitivity Summary for Bidirectional Swap of 131072 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

128 3.5555e-02 3.4721e-05 7.37 0.37 0.29 1.06

256 2.0788e-02 4.0602e-05 12.61 0.30 0.28 0.82

512 2.3050e-02 9.0039e-05 11.37 0.09 0.07 0.28

1024 1.1575e-02 9.0428e-05 22.65 0.09 0.06 0.29

2048 5.7134e-03 8.9272e-05 45.88 0.11 0.07 0.32

4096 2.8642e-03 8.9506e-05 91.52 0.10 0.08 0.33

8192 1.4554e-03 9.0962e-05 180.12 1.15 0.09 10.47

16384 8.9020e-04 1.1127e-04 294.48 0.92 0.11 8.14

32768 7.4220e-04 1.8555e-04 353.20 3.24 0.08 31.60

65536 6.8200e-04 3.4100e-04 384.38 2.15 0.06 21.15

131072 6.1980e-04 6.1980e-04 422.95 3.55 0.05 35.14

Five Fastest
Protocols

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

128 3 6 2 0 7

256 2 6 3 0 7

512 3 2 6 7 1

1024 3 2 6 0 1

2048 3 2 6 0 1

4096 6 0 2 3 1

8192 2 1 6 3 9

16384 2 3 6 1 9

32768 2 9 3 1 8

65536 6 3 8 2 7

131072 2 6 5 1 3

Number of Proctocols With
Runtimes Within X% of Min

Msg Size 1% 5% 25%

128 1 2 4

256 2 3 4

512 3 3 8

1024 3 3 8

2048 1 3 8

4096 4 4 8

8192 2 4 7

16384 1 2 7

32768 1 1 9

65536 1 5 9

131072 1 6 9

Protocol Sensitivity Summary for Bidirectional Swap of 131072 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

128 3.7350e-02 3.6475e-05 7.02 0.32 0.22 0.97

256 2.1025e-02 4.1064e-05 12.47 0.29 0.26 0.80

512 2.3036e-02 8.9986e-05 11.38 0.09 0.06 0.29

1024 1.1583e-02 9.0495e-05 22.63 0.09 0.06 0.28

2048 5.8774e-03 9.1834e-05 44.60 0.08 0.04 0.27

4096 2.8236e-03 8.8237e-05 92.84 0.11 0.09 0.35

8192 1.4387e-03 8.9917e-05 182.21 0.11 0.08 0.39

16384 8.6438e-04 1.0805e-04 303.27 0.09 0.04 0.24

32768 7.3758e-04 1.8440e-04 355.41 0.06 0.03 0.24

65536 6.4452e-04 3.2226e-04 406.73 0.06 0.04 0.24

131072 6.0460e-04 6.0460e-04 433.58 0.06 0.04 0.30

Five Fastest
Protocols

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

128 3 6 2 0 7

256 6 2 3 0 7

512 6 3 2 7 1

1024 2 6 3 0 1

2048 6 2 3 1 9

4096 6 2 3 0 1

8192 1 2 6 3 0

16384 3 7 9 6 2

32768 9 6 7 3 2

65536 2 3 4 5 9

131072 3 4 2 7 6

Number of Proctocols With
Runtimes Within X% of Min

Msg Size 1% 5% 25%

128 1 2 7

256 2 3 4

512 2 3 8

1024 3 3 8

2048 2 7 8

4096 3 4 8

8192 1 5 8

16384 1 6 10

32768 1 6 10

65536 2 6 10

131072 1 9 9

Protocol Sensitivity Summary for Bidirectional Swap of 131072 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

128 3.0505e-02 2.9790e-05 8.59 0.33 0.33 1.24

256 1.8532e-02 3.6196e-05 14.15 0.26 0.28 1.03

512 2.0425e-02 7.9787e-05 12.83 0.16 0.14 0.74

1024 1.0669e-02 8.3352e-05 24.57 0.12 0.07 0.64

2048 5.5810e-03 8.7203e-05 46.97 0.08 0.07 0.41

4096 2.8798e-03 8.9994e-05 91.03 0.06 0.06 0.19

8192 1.7334e-03 1.0834e-04 151.23 0.07 0.06 0.24

16384 1.3456e-03 1.6820e-04 194.82 0.10 0.09 0.21

32768 1.1754e-03 2.9385e-04 223.03 0.07 0.03 0.29

65536 1.1034e-03 5.5170e-04 237.58 0.08 0.03 0.40

131072 1.0686e-03 1.0686e-03 245.32 0.07 0.01 0.44

Five Fastest
Protocols

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

128 2 3 5 4 6

256 5 3 2 4 6

512 5 2 3 4 6

1024 3 4 2 5 9

2048 3 4 5 2 6

4096 2 3 4 5 1

8192 6 8 4 5 7

16384 6 1 7 8 2

32768 4 8 2 3 9

65536 4 2 5 8 3

131072 8 3 2 5 4

Number of Proctocols With
Runtimes Within X% of Min

Msg Size 1% 5% 25%

128 4 4 5

256 2 4 5

512 3 4 9

1024 3 4 9

2048 4 5 9

4096 3 5 10

8192 1 4 10

16384 1 1 10

32768 2 6 9

65536 3 7 9

131072 5 8 9

Protocol Sensitivity Summary for Bidirectional Swap of 131072 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

128 3.0418e-02 2.9705e-05 8.62 0.33 0.32 1.23

256 1.8681e-02 3.6486e-05 14.03 0.25 0.26 1.01

512 2.0046e-02 7.8304e-05 13.08 0.17 0.16 0.77

1024 1.0164e-02 7.9405e-05 25.79 0.16 0.14 0.74

2048 5.2630e-03 8.2234e-05 49.81 0.13 0.09 0.69

4096 2.7688e-03 8.6525e-05 94.68 0.07 0.03 0.34

8192 1.4586e-03 9.1163e-05 179.72 1.54 0.03 14.61

16384 9.1220e-04 1.1402e-04 287.38 0.62 0.19 4.86

32768 7.2680e-04 1.8170e-04 360.68 3.55 0.19 33.91

65536 6.3080e-04 3.1540e-04 415.57 0.48 0.20 3.25

131072 6.0080e-04 6.0080e-04 436.32 0.77 0.13 6.63

Five Fastest
Protocols

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

128 3 5 2 4 6

256 3 2 5 4 6

512 4 5 2 3 6

1024 4 5 2 3 9

2048 2 4 5 3 9

4096 2 5 4 6 3

8192 2 4 5 6 3

16384 2 5 1 6 7

32768 5 6 2 9 8

65536 4 5 9 2 3

131072 5 4 9 1 3

Number of Proctocols With
Runtimes Within X% of Min

Msg Size 1% 5% 25%

128 3 4 5

256 3 4 5

512 3 4 9

1024 2 4 9

2048 2 4 9

4096 3 6 9

8192 2 6 7

16384 1 4 7

32768 1 3 7

65536 1 3 6

131072 1 4 7

Protocol Sensitivity Summary for Bidirectional Swap of 131072 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

128 3.2529e-02 3.1766e-05 8.06 0.25 0.27 0.84

256 1.9321e-02 3.7737e-05 13.57 0.24 0.23 0.89

512 2.1617e-02 8.4442e-05 12.13 0.12 0.11 0.62

1024 1.0744e-02 8.3937e-05 24.40 0.13 0.11 0.64

2048 5.4558e-03 8.5247e-05 48.05 0.13 0.11 0.62

4096 2.8459e-03 8.8936e-05 92.11 0.10 0.07 0.43

8192 1.4685e-03 9.1783e-05 178.51 0.07 0.06 0.15

16384 8.6502e-04 1.0813e-04 303.05 0.05 0.03 0.21

32768 7.1218e-04 1.7804e-04 368.09 0.08 0.04 0.25

65536 6.2214e-04 3.1107e-04 421.36 0.08 0.03 0.29

131072 5.8254e-04 5.8254e-04 450.00 0.07 0.06 0.34

Five Fastest
Protocols

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

128 4 5 3 2 6

256 4 2 5 3 6

512 2 4 5 3 6

1024 4 2 3 5 6

2048 4 2 3 5 6

4096 6 0 4 2 5

8192 1 6 0 4 2

16384 4 3 2 5 6

32768 3 9 5 2 4

65536 3 5 2 4 9

131072 4 2 9 3 5

Number of Proctocols With
Runtimes Within X% of Min

Msg Size 1% 5% 25%

128 3 4 5

256 1 4 6

512 2 4 9

1024 2 4 9

2048 2 4 9

4096 1 3 9

8192 1 3 10

16384 2 6 10

32768 3 6 9

65536 3 6 9

131072 4 5 9

DISCUSSION

The AlphaServer SC processing node consists of four processors. In these tests, we examine MPI communication performance between processors in a node when all processors in the node are communicating. 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.