现在，计算机CPU运行速度的快速发展已经远远超过了内存的访问速度。越来越多的程序性能被内存带宽所限制，而不是计算机的CPU运行速率。
Stream benchmark是一个简单的合成基准测试程序，衡量内存带宽（MB /秒）和相应的内核向量的计算速度。
Each of the four tests adds independent information to the results:
1. “copy”：在没有算术的衡量传输速率；
2. “Scale”
- ``Copy'' measures transfer rates in the absence of arithmetic.
- ``Scale'' adds a simple arithmetic operation.
- ``Sum'' adds a third operand to allow multiple load/store ports on vector machines to be tested.
- ``Triad'' allows chained/overlapped/fused multiply/add operations.
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[root@RedHat stream]# make gcc -O2 stream.c -o stream [root@RedHat stream]# ls Makefile stream stream.c stream.f [root@RedHat stream]# ./stream ------------------------------------------------------------- STREAM version $Revision: 5.9 $ ------------------------------------------------------------- This system uses 8 bytes per DOUBLE PRECISION word. ------------------------------------------------------------- Array size = 2000000, Offset = 0 Total memory required = 45.8 MB. Each test is run 10 times, but only the *best* time for each is used. ------------------------------------------------------------- Printing one line per active thread.... ------------------------------------------------------------- Your clock granularity/precision appears to be 6 microseconds. Each test below will take on the order of 17340 microseconds. (= 2890 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 Rate (MB/s) Avg time Min time Max time Copy: 2264.0171 0.0154 0.0141 0.0169 Scale: 2212.8422 0.0154 0.0145 0.0164 Add: 2936.3309 0.0196 0.0163 0.0214 Triad: 2673.8123 0.0199 0.0180 0.0216 ------------------------------------------------------------- Solution Validates ------------------------------------------------------------- [root@RedHat stream]# |