Talk:Memory benchmarking

The results are being pessimized by not compiling with -O2 or -O3, gcc 
 
% ./streamOO # compiled with gcc -O1 (default)
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STREAM version $Revision: 5.10 $
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This system uses 8 bytes per array element.
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Array size = 80000000 (elements), Offset = 0 (elements)
Memory per array = 610.4 MiB (= 0.6 GiB).
Total memory required = 1831.1 MiB (= 1.8 GiB).
Each kernel will be executed 20 times.
 The *best* time for each kernel (excluding the first iteration)
 will be used to compute the reported bandwidth.
-------------------------------------------------------------
Your clock granularity/precision appears to be 1 microseconds.
Each test below will take on the order of 102530 microseconds.
   (= 102530 clock ticks)
Increase the size of the arrays if this shows that
you are not getting at least 20 clock ticks per test.
-------------------------------------------------------------
WARNING -- The above is only a rough guideline.
For best results, please be sure you know the
precision of your system timer.
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Function    Best Rate MB/s  Avg time     Min time     Max time
Copy:           78073.3     0.025361     0.016395     0.043100
Scale:          46793.9     0.039523     0.027354     0.071281
Add:            59053.5     0.053389     0.032513     0.131950
Triad:          59999.9     0.047117     0.032000     0.083272
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Solution Validates: avg error less than 1.000000e-13 on all three arrays
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% ./stream3 # compiled with gcc -O3
-------------------------------------------------------------
STREAM version $Revision: 5.10 $
-------------------------------------------------------------
This system uses 8 bytes per array element.
-------------------------------------------------------------
Array size = 80000000 (elements), Offset = 0 (elements)
Memory per array = 610.4 MiB (= 0.6 GiB).
Total memory required = 1831.1 MiB (= 1.8 GiB).
Each kernel will be executed 20 times.
 The *best* time for each kernel (excluding the first iteration)
 will be used to compute the reported bandwidth.
-------------------------------------------------------------
Your clock granularity/precision appears to be 1 microseconds.
Each test below will take on the order of 27529 microseconds.
   (= 27529 clock ticks)
Increase the size of the arrays if this shows that
you are not getting at least 20 clock ticks per test.
-------------------------------------------------------------
WARNING -- The above is only a rough guideline.
For best results, please be sure you know the
precision of your system timer.
-------------------------------------------------------------
Function    Best Rate MB/s  Avg time     Min time     Max time
Copy:           91584.9     0.016514     0.013976     0.025457
Scale:          66969.9     0.023857     0.019113     0.041276
Add:            74011.0     0.037041     0.025942     0.118478
Triad:          76138.9     0.035763     0.025217     0.092531
-------------------------------------------------------------
Solution Validates: avg error less than 1.000000e-13 on all three arrays
-------------------------------------------------------------