Linux下stream内存带宽测试参数和示例详解附源码（总结）
高高雅
一、简介
本文通过实例详细讲解各编译参数，方便读者快速掌握。stream是一套综合性能测试程序集，通过fortran和c两种高级且高效的语言编写完成，由于这两种语言在数学计算方面的高效率， 使得stream测试例程可以充分发挥出内存的能力。
二、使用简介
stream测试得到的是可持续运行的内存带宽最大值，而并不是一般的硬件厂商提供的理论最大值，具有如下特点：
1.主要有四种数组的运算，测试到内存带宽的性能分别是:数组的复制(Copy)、数组的尺度变换(Scale)、数组的矢量求和(Add)、数组的复合矢量求和(Triad)。
2. 数组的值采用了双精度（8个字节）
2.1 测试内容简介
| 测试内容 | 解析 |
|---|---|
| Copy | 是复制操作，即从内存单元中读取一个数，并复制到其他内存单元中，两次访问内存操作 |
| Scale | 是乘法操作，即从内存单元中读取一个数，与常数相乘，得到的记过存到其他内存单元，两次访问内存操作 |
| Add | 是加法操作，从两个内存单元中分别读取两个数，将其进行加法操作后，得到的结果写入另一个内存单元中，3次访问内存操作 |
| Triad | 是前面三种的结合，先从内存中读取一个数，与一个常数相乘得到一个乘积，然后从另一个内存单元中读取一个数与刚才乘积结果相加，得到的结果写入内存。3次访问内存操作 |
测试结果一般的规律是Add > Triad > Copy > Scale。一次Add操作需要访问三次内存（两个读操作，一个写操作），Triad操作也需要三次访问内存， Copy和Scale操作需要两次访问内存。单位操作内，访问内存次数越多，越能够掩盖访存延迟，带宽越大。
单核Stream测试，影响的因素除了内存控制器能力外，还有Core的ROB、Load/Store对其影响，因此不是单纯的内存带宽性能测试。
而多核Stream测试，通过多核同时发出大量内存访问请求，能够更加饱和地访问内存，从而测试到内存带宽的极限性能。
2.2 编译参数简介
stream测试首先通过带不同的编译参数用于达到不同的测试结果，具体的编译参数如下：
| 参数 | 解析 |
|---|---|
| -O3 | 编译器编译优化级别 |
| -mcmodel=small | 当单个Memory Array Size 大于2GB时需要设置此参数 |
| -fopenmp | 适应多处理器环境；开启后，程序默认线程为CPU线程数 |
| -DSTREAM_ARRAY_SIZE=200000000 | 指定计算中a[],b[],c[]数组的大小，部分版本stream为-DN=2000000形式设置 |
| -DNTIMES=30 | 执行的次数，并且从这些结果中选最优值 |
| -DOFFSET=4096 | 数组的偏移，一般可以不定义 |
注意：
1、运行时动态指定运行的进程数：
export OMP_NUM_THREADS=8 #8为自定义的要使用的处理器数量
2、设置数组DSTREAM_ARRAY_SIZE值
这个参数是对测试结果影响最大，也是最需要关注的一个参数，它用来指定计算中a[],b[],c[]数组的大小，且数组的值采用了双精度（8个字节）。设置数组的维数 STREAM ARRAY_SIZE 定义时需要注意以下几点：
（1）要充分考虑内存容量的需求，粗略估计是 STREAM ARRAY_SIZE × 8（双精度） × 3 （三个数组）<= 0.6*M；M 是用户的可用内存。
（2）要保证测试过程中，必须设置测试数组大小远大于CPU 最高级缓存（一般为L3 Cache）的大小，否则就是测试CPU缓存的吞吐性能(带宽值最大数组大小要大于缓存的 4 倍)，而非内存吞吐性能。
（3）为了保证测试可以持续一段时间，测试过程中内存带宽可以达到一定的最大值， 从而避免得不到实际最大峰值的情况，如果四项测试中有完成时间小于20微秒的情况，就需要适当的增大测试数组的维度 STREAM ARRAY_SIZE。
（4）5.9版本默认值-DN=2000000，5.10版本，参数名变为-DSTREAM_ARRAY_SIZE，默认值10000000）。注意：。
3、设置-mcmodel=small报错
新的gcc已经不支持‘-mcmodel=medium’参数了，可以改为“-mcmodel=large”、“-mcmodel=small”、“-mcmodel=tiny”
2.3 具体参数示例
本地编译执行：
[root@localhost /]# gcc -O3 -mtune=native -march=native -fopenmp -DSTREAM_ARRAY_SIZE=200000000 -DNTIMES=100 stream.c -o stream
[root@localhost /]# ./stream
交叉编译在其他目标机器执行：
[root@localhost /]# aarch64-linux-gnu-gcc -O3 --static -fno-PIC -mcmodel=large -fopenmp -DSTREAM_ARRAY_SIZE=200000000 -DNTIMES=30 stream.c -o stream
[root@localhost /]# ./stream
执行结果如下：
[root@localhost /]# gcc -O3 -mtune=native -march=native -fopenmp -DN=200000000 -DNTIMES=100 stream.c -o stream
[root@localhost /]# ./stream
-------------------------------------------------------------
STREAM version $Revision: 5.10 $
-------------------------------------------------------------
This system uses 8 bytes per array element.
-------------------------------------------------------------
***** WARNING: ******
It appears that you set the preprocessor variable N when compiling this code.
This version of the code uses the preprocesor variable STREAM_ARRAY_SIZE to control the array size
Reverting to default value of STREAM_ARRAY_SIZE=10000000
***** WARNING: ******
Array size = 10000000 (elements), Offset = 0 (elements)
Memory per array = 76.3 MiB (= 0.1 GiB).
Total memory required = 228.9 MiB (= 0.2 GiB).
Each kernel will be executed 100 times.
The *best* time for each kernel (excluding the first iteration)
will be used to compute the reported bandwidth.
-------------------------------------------------------------
Number of Threads requested = 6
Number of Threads counted = 6
-------------------------------------------------------------
Your clock granularity/precision appears to be 1 microseconds.
Each test below will take on the order of 11274 microseconds.
(= 11274 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: 13704.6 0.011720 0.011675 0.011816
Scale: 10937.1 0.014686 0.014629 0.015018
Add: 12362.1 0.019471 0.019414 0.019872
Triad: 12369.2 0.019462 0.019403 0.020019
-------------------------------------------------------------
Solution Validates: avg error less than 1.000000e-13 on all three arrays
三、源码下载及使用
将代码直接复制到新建文本stream.c中，直接用上面所带参数进行编译执行即可。
/*-----------------------------------------------------------------------*/
/* Program: STREAM */
/* Revision: $Id: stream.c,v 5.10 2013/01/17 16:01:06 mccalpin Exp mccalpin $ */
/* Original code developed by John D. McCalpin */
/* Programmers: John D. McCalpin */
/* Joe R. Zagar */
/* */
/* This program measures memory transfer rates in MB/s for simple */
/* computational kernels coded in C. */
/*-----------------------------------------------------------------------*/
/* Copyright 1991-2013: John D. McCalpin */
/*-----------------------------------------------------------------------*/
/* License: */
/* 1. You are free to use this program and/or to redistribute */
/* this program. */
/* 2. You are free to modify this program for your own use, */
/* including commercial use, subject to the publication */
/* restrictions in item 3. */
/* 3. You are free to publish results obtained from running this */
/* program, or from works that you derive from this program, */
/* with the following limitations: */
/* 3a. In order to be referred to as "STREAM benchmark results", */
/* published results must be in conformance to the STREAM */
/* Run Rules, (briefly reviewed below) published at */
/* http://www.cs.virginia.edu/stream/ref.html */
/* and incorporated herein by reference. */
/* As the copyright holder, John McCalpin retains the */
/* right to determine conformity with the Run Rules. */
/* 3b. Results based on modified source code or on runs not in */
/* accordance with the STREAM Run Rules must be clearly */
/* labelled whenever they are published. Examples of */
/* proper labelling include: */
/* "tuned STREAM benchmark results" */
/* "based on a variant of the STREAM benchmark code" */
/* Other comparable, clear, and reasonable labelling is */
/* acceptable. */
/* 3c. Submission of results to the STREAM benchmark web site */
/* is encouraged, but not required. */
/* 4. Use of this program or creation of derived works based on this */
/* program constitutes acceptance of these licensing restrictions. */
/* 5. Absolutely no warranty is expressed or implied. */
/*-----------------------------------------------------------------------*/
# include <stdio.h>
# include <unistd.h>
# include <math.h>
# include <float.h>
# include <limits.h>
# include <sys/time.h>
/*-----------------------------------------------------------------------
* INSTRUCTIONS:
*
* 1) STREAM requires different amounts of memory to run on different
* systems, depending on both the system cache size(s) and the
* granularity of the system timer.
* You should adjust the value of 'STREAM_ARRAY_SIZE' (below)
* to meet *both* of the following criteria:
* (a) Each array must be at least 4 times the size of the
* available cache memory. I don't worry about the difference
* between 10^6 and 2^20, so in practice the minimum array size
* is about 3.8 times the cache size.
* Example 1: One Xeon E3 with 8 MB L3 cache
* STREAM_ARRAY_SIZE should be >= 4 million, giving
* an array size of 30.5 MB and a total memory requirement
* of 91.5 MB.
* Example 2: Two Xeon E5's with 20 MB L3 cache each (using OpenMP)
* STREAM_ARRAY_SIZE should be >= 20 million, giving
* an array size of 153 MB and a total memory requirement
* of 458 MB.
* (b) The size should be large enough so that the 'timing calibration'
* output by the program is at least 20 clock-ticks.
* Example: most versions of Windows have a 10 millisecond timer
* granularity. 20 "ticks" at 10 ms/tic is 200 milliseconds.
* If the chip is capable of 10 GB/s, it moves 2 GB in 200 msec.
* This means the each array must be at least 1 GB, or 128M elements.
*
* Version 5.10 increases the default array size from 2 million
* elements to 10 million elements in response to the increasing
* size of L3 caches. The new default size is large enough for caches
* up to 20 MB.
* Version 5.10 changes the loop index variables from "register int"
* to "ssize_t", which allows array indices >2^32 (4 billion)
* on properly configured 64-bit systems. Additional compiler options
* (such as "-mcmodel=medium") may be required for large memory runs.
*
* Array size can be set at compile time without modifying the source
* code for the (many) compilers that support preprocessor definitions
* on the compile line. E.g.,
* gcc -O -DSTREAM_ARRAY_SIZE=100000000 stream.c -o stream.100M
* will override the default size of 10M with a new size of 100M elements
* per array.
*/
#ifndef STREAM_ARRAY_SIZE
# define STREAM_ARRAY_SIZE 10000000
#endif
/* 2) STREAM runs each kernel "NTIMES" times and reports the *best* result
* for any iteration after the first, therefore the minimum value
* for NTIMES is 2.
* There are no rules on maximum allowable values for NTIMES, but
* values larger than the default are unlikely to noticeably
* increase the reported performance.
* NTIMES can also be set on the compile line without changing the source
* code using, for example, "-DNTIMES=7".
*/
#ifdef NTIMES
#if NTIMES<=1
# define NTIMES 10
#endif
#endif
#ifndef NTIMES
# define NTIMES 10
#endif
/* Users are allowed to modify the "OFFSET" variable, which *may* change the
* relative alignment of the arrays (though compilers may change the
* effective offset by making the arrays non-contiguous on some systems).
* Use of non-zero values for OFFSET can be especially helpful if the
* STREAM_ARRAY_SIZE is set to a value close to a large power of 2.
* OFFSET can also be set on the compile line without changing the source
* code using, for example, "-DOFFSET=56".
*/
#ifndef OFFSET
# define OFFSET 0
#endif
/*
* 3) Compile the code with optimization. Many compilers generate
* unreasonably bad code before the optimizer tightens things up.
* If the results are unreasonably good, on the other hand, the
* optimizer might be too smart for me!
*
* For a simple single-core version, try compiling with:
* cc -O stream.c -o stream
* This is known to work on many, many systems....
*
* To use multiple cores, you need to tell the compiler to obey the OpenMP
* directives in the code. This varies by compiler, but a common example is
* gcc -O -fopenmp stream.c -o stream_omp
* The environment variable OMP_NUM_THREADS allows runtime control of the
* number of threads/cores used when the resulting "stream_omp" program
* is executed.
*
* To run with single-precision variables and arithmetic, simply add
* -DSTREAM_TYPE=float
* to the compile line.
* Note that this changes the minimum array sizes required --- see (1) above.
*
* The preprocessor directive "TUNED" does not do much -- it simply causes the
* code to call separate functions to execute each kernel. Trivial versions
* of these functions are provided, but they are *not* tuned -- they just
* provide predefined interfaces to be replaced with tuned code.
*
*
* 4) Optional: Mail the results to mccalpin@cs.virginia.edu
* Be sure to include info that will help me understand:
* a) the computer hardware configuration (e.g., processor model, memory type)
* b) the compiler name/version and compilation flags
* c) any run-time information (such as OMP_NUM_THREADS)
* d) all of the output from the test case.
*
* Thanks!
*
*-----------------------------------------------------------------------*/
# define HLINE "-------------------------------------------------------------\n"
# ifndef MIN
# define MIN(x,y) ((x)<(y)?(x):(y))
# endif
# ifndef MAX
# define MAX(x,y) ((x)>(y)?(x):(y))
# endif
#ifndef STREAM_TYPE
#define STREAM_TYPE double
#endif
static STREAM_TYPE a[STREAM_ARRAY_SIZE+OFFSET],
b[STREAM_ARRAY_SIZE+OFFSET],
c[STREAM_ARRAY_SIZE+OFFSET];
static double avgtime[4] = {0}, maxtime[4] = {0},
mintime[4] = {FLT_MAX,FLT_MAX,FLT_MAX,FLT_MAX};
static char *label[4] = {"Copy: ", "Scale: ",
"Add: ", "Triad: "};
static double bytes[4] = {
2 * sizeof(STREAM_TYPE) * STREAM_ARRAY_SIZE,
2 * sizeof(STREAM_TYPE) * STREAM_ARRAY_SIZE,
3 * sizeof(STREAM_TYPE) * STREAM_ARRAY_SIZE,
3 * sizeof(STREAM_TYPE) * STREAM_ARRAY_SIZE
};
extern double mysecond();
extern void checkSTREAMresults();
#ifdef TUNED
extern void tuned_STREAM_Copy();
extern void tuned_STREAM_Scale(STREAM_TYPE scalar);
extern void tuned_STREAM_Add();
extern void tuned_STREAM_Triad(STREAM_TYPE scalar);
#endif
#ifdef _OPENMP
extern int omp_get_num_threads();
#endif
int
main()
{
int quantum, checktick();
int BytesPerWord;
int k;
ssize_t j;
STREAM_TYPE scalar;
double t, times[4][NTIMES];
/* --- SETUP --- determine precision and check timing --- */
printf(HLINE);
printf("STREAM version $Revision: 5.10 $\n");
printf(HLINE);
BytesPerWord = sizeof(STREAM_TYPE);
printf("This system uses %d bytes per array element.\n",
BytesPerWord);
printf(HLINE);
#ifdef N
printf("***** WARNING: ******\n");
printf(" It appears that you set the preprocessor variable N when compiling this code.\n");
printf(" This version of the code uses the preprocesor variable STREAM_ARRAY_SIZE to control the array size\n");
printf(" Reverting to default value of STREAM_ARRAY_SIZE=%llu\n",(unsigned long long) STREAM_ARRAY_SIZE);
printf("***** WARNING: ******\n");
#endif
printf("Array size = %llu (elements), Offset = %d (elements)\n" , (unsigned long long) STREAM_ARRAY_SIZE, OFFSET);
printf("Memory per array = %.1f MiB (= %.1f GiB).\n",
BytesPerWord * ( (double) STREAM_ARRAY_SIZE / 1024.0/1024.0),
BytesPerWord * ( (double) STREAM_ARRAY_SIZE / 1024.0/1024.0/1024.0));
printf("Total memory required = %.1f MiB (= %.1f GiB).\n",
(3.0 * BytesPerWord) * ( (double) STREAM_ARRAY_SIZE / 1024.0/1024.),
(3.0 * BytesPerWord) * ( (double) STREAM_ARRAY_SIZE / 1024.0/1024./1024.));
printf("Each kernel will be executed %d times.\n", NTIMES);
printf(" The *best* time for each kernel (excluding the first iteration)\n");
printf(" will be used to compute the reported bandwidth.\n");
#ifdef _OPENMP
printf(HLINE);
#pragma omp parallel
{
#pragma omp master
{
k = omp_get_num_threads();
printf ("Number of Threads requested = %i\n",k);
}
}
#endif
#ifdef _OPENMP
k = 0;
#pragma omp parallel
#pragma omp atomic
k++;
printf ("Number of Threads counted = %i\n",k);
#endif
/* Get initial value for system clock. */
#pragma omp parallel for
for (j=0; j<STREAM_ARRAY_SIZE; j++) {
a[j] = 1.0;
b[j] = 2.0;
c[j] = 0.0;
}
printf(HLINE);
if ( (quantum = checktick()) >= 1)
printf("Your clock granularity/precision appears to be "
"%d microseconds.\n", quantum);
else {
printf("Your clock granularity appears to be "
"less than one microsecond.\n");
quantum = 1;
}
t = mysecond();
#pragma omp parallel for
for (j = 0; j < STREAM_ARRAY_SIZE; j++)
a[j] = 2.0E0 * a[j];
t = 1.0E6 * (mysecond() - t);
printf("Each test below will take on the order"
" of %d microseconds.\n", (int) t );
printf(" (= %d clock ticks)\n", (int) (t/quantum) );
printf("Increase the size of the arrays if this shows that\n");
printf("you are not getting at least 20 clock ticks per test.\n");
printf(HLINE);
printf("WARNING -- The above is only a rough guideline.\n");
printf("For best results, please be sure you know the\n");
printf("precision of your system timer.\n");
printf(HLINE);
/* --- MAIN LOOP --- repeat test cases NTIMES times --- */
scalar = 3.0;
for (k=0; k<NTIMES; k++)
{
times[0][k] = mysecond();
#ifdef TUNED
tuned_STREAM_Copy();
#else
#pragma omp parallel for
for (j=0; j<STREAM_ARRAY_SIZE; j++)
c[j] = a[j];
#endif
times[0][k] = mysecond() - times[0][k];
times[1][k] = mysecond();
#ifdef TUNED
tuned_STREAM_Scale(scalar);
#else
#pragma omp parallel for
for (j=0; j<STREAM_ARRAY_SIZE; j++)
b[j] = scalar*c[j];
#endif
times[1][k] = mysecond() - times[1][k];
times[2][k] = mysecond();
#ifdef TUNED
tuned_STREAM_Add();
#else
#pragma omp parallel for
for (j=0; j<STREAM_ARRAY_SIZE; j++)
c[j] = a[j]+b[j];
#endif
times[2][k] = mysecond() - times[2][k];
times[3][k] = mysecond();
#ifdef TUNED
tuned_STREAM_Triad(scalar);
#else
#pragma omp parallel for
for (j=0; j<STREAM_ARRAY_SIZE; j++)
a[j] = b[j]+scalar*c[j];
#endif
times[3][k] = mysecond() - times[3][k];
}
/* --- SUMMARY --- */
for (k=1; k<NTIMES; k++) /* note -- skip first iteration */
{
for (j=0; j<4; j++)
{
avgtime[j] = avgtime[j] + times[j][k];
mintime[j] = MIN(mintime[j], times[j][k]);
maxtime[j] = MAX(maxtime[j], times[j][k]);
}
}
printf("Function Best Rate MB/s Avg time Min time Max time\n");
for (j=0; j<4; j++) {
avgtime[j] = avgtime[j]/(double)(NTIMES-1);
printf("%s%12.1f %11.6f %11.6f %11.6f\n", label[j],
1.0E-06 * bytes[j]/mintime[j],
avgtime[j],
mintime[j],
maxtime[j]);
}
printf(HLINE);
/* --- Check Results --- */
checkSTREAMresults();
printf(HLINE);
return 0;
}
# define M 20
int
checktick()
{
int i, minDelta, Delta;
double t1, t2, timesfound[M];
/* Collect a sequence of M unique time values from the system. */
for (i = 0; i < M; i++) {
t1 = mysecond();
while( ((t2=mysecond()) - t1) < 1.0E-6 )
;
timesfound[i] = t1 = t2;
}
/*
* Determine the minimum difference between these M values.
* This result will be our estimate (in microseconds) for the
* clock granularity.
*/
minDelta = 1000000;
for (i = 1; i < M; i++) {
Delta = (int)( 1.0E6 * (timesfound[i]-timesfound[i-1]));
minDelta = MIN(minDelta, MAX(Delta,0));
}
return(minDelta);
}
/* A gettimeofday routine to give access to the wall
clock timer on most UNIX-like systems. */
#include <sys/time.h>
double mysecond()
{
struct timeval tp;
struct timezone tzp;
int i;
i = gettimeofday(&tp,&tzp);
return ( (double) tp.tv_sec + (double) tp.tv_usec * 1.e-6 );
}
#ifndef abs
#define abs(a) ((a) >= 0 ? (a) : -(a))
#endif
void checkSTREAMresults ()
{
STREAM_TYPE aj,bj,cj,scalar;
STREAM_TYPE aSumErr,bSumErr,cSumErr;
STREAM_TYPE aAvgErr,bAvgErr,cAvgErr;
double epsilon;
ssize_t j;
int k,ierr,err;
/* reproduce initialization */
aj = 1.0;
bj = 2.0;
cj = 0.0;
/* a[] is modified during timing check */
aj = 2.0E0 * aj;
/* now execute timing loop */
scalar = 3.0;
for (k=0; k<NTIMES; k++)
{
cj = aj;
bj = scalar*cj;
cj = aj+bj;
aj = bj+scalar*cj;
}
/* accumulate deltas between observed and expected results */
aSumErr = 0.0;
bSumErr = 0.0;
cSumErr = 0.0;
for (j=0; j<STREAM_ARRAY_SIZE; j++) {
aSumErr += abs(a[j] - aj);
bSumErr += abs(b[j] - bj);
cSumErr += abs(c[j] - cj);
// if (j == 417) printf("Index 417: c[j]: %f, cj: %f\n",c[j],cj); // MCCALPIN
}
aAvgErr = aSumErr / (STREAM_TYPE) STREAM_ARRAY_SIZE;
bAvgErr = bSumErr / (STREAM_TYPE) STREAM_ARRAY_SIZE;
cAvgErr = cSumErr / (STREAM_TYPE) STREAM_ARRAY_SIZE;
if (sizeof(STREAM_TYPE) == 4) {
epsilon = 1.e-6;
}
else if (sizeof(STREAM_TYPE) == 8) {
epsilon = 1.e-13;
}
else {
printf("WEIRD: sizeof(STREAM_TYPE) = %lu\n",sizeof(STREAM_TYPE));
epsilon = 1.e-6;
}
err = 0;
if (abs(aAvgErr/aj) > epsilon) {
err++;
printf ("Failed Validation on array a[], AvgRelAbsErr > epsilon (%e)\n",epsilon);
printf (" Expected Value: %e, AvgAbsErr: %e, AvgRelAbsErr: %e\n",aj,aAvgErr,abs(aAvgErr)/aj);
ierr = 0;
for (j=0; j<STREAM_ARRAY_SIZE; j++) {
if (abs(a[j]/aj-1.0) > epsilon) {
ierr++;
#ifdef VERBOSE
if (ierr < 10) {
printf(" array a: index: %ld, expected: %e, observed: %e, relative error: %e\n",
j,aj,a[j],abs((aj-a[j])/aAvgErr));
}
#endif
}
}
printf(" For array a[], %d errors were found.\n",ierr);
}
if (abs(bAvgErr/bj) > epsilon) {
err++;
printf ("Failed Validation on array b[], AvgRelAbsErr > epsilon (%e)\n",epsilon);
printf (" Expected Value: %e, AvgAbsErr: %e, AvgRelAbsErr: %e\n",bj,bAvgErr,abs(bAvgErr)/bj);
printf (" AvgRelAbsErr > Epsilon (%e)\n",epsilon);
ierr = 0;
for (j=0; j<STREAM_ARRAY_SIZE; j++) {
if (abs(b[j]/bj-1.0) > epsilon) {
ierr++;
#ifdef VERBOSE
if (ierr < 10) {
printf(" array b: index: %ld, expected: %e, observed: %e, relative error: %e\n",
j,bj,b[j],abs((bj-b[j])/bAvgErr));
}
#endif
}
}
printf(" For array b[], %d errors were found.\n",ierr);
}
if (abs(cAvgErr/cj) > epsilon) {
err++;
printf ("Failed Validation on array c[], AvgRelAbsErr > epsilon (%e)\n",epsilon);
printf (" Expected Value: %e, AvgAbsErr: %e, AvgRelAbsErr: %e\n",cj,cAvgErr,abs(cAvgErr)/cj);
printf (" AvgRelAbsErr > Epsilon (%e)\n",epsilon);
ierr = 0;
for (j=0; j<STREAM_ARRAY_SIZE; j++) {
if (abs(c[j]/cj-1.0) > epsilon) {
ierr++;
#ifdef VERBOSE
if (ierr < 10) {
printf(" array c: index: %ld, expected: %e, observed: %e, relative error: %e\n",
j,cj,c[j],abs((cj-c[j])/cAvgErr));
}
#endif
}
}
printf(" For array c[], %d errors were found.\n",ierr);
}
if (err == 0) {
printf ("Solution Validates: avg error less than %e on all three arrays\n",epsilon);
}
#ifdef VERBOSE
printf ("Results Validation Verbose Results: \n");
printf (" Expected a(1), b(1), c(1): %f %f %f \n",aj,bj,cj);
printf (" Observed a(1), b(1), c(1): %f %f %f \n",a[1],b[1],c[1]);
printf (" Rel Errors on a, b, c: %e %e %e \n",abs(aAvgErr/aj),abs(bAvgErr/bj),abs(cAvgErr/cj));
#endif
}
#ifdef TUNED
/* stubs for "tuned" versions of the kernels */
void tuned_STREAM_Copy()
{
ssize_t j;
#pragma omp parallel for
for (j=0; j<STREAM_ARRAY_SIZE; j++)
c[j] = a[j];
}
void tuned_STREAM_Scale(STREAM_TYPE scalar)
{
ssize_t j;
#pragma omp parallel for
for (j=0; j<STREAM_ARRAY_SIZE; j++)
b[j] = scalar*c[j];
}
void tuned_STREAM_Add()
{
ssize_t j;
#pragma omp parallel for
for (j=0; j<STREAM_ARRAY_SIZE; j++)
c[j] = a[j]+b[j];
}
void tuned_STREAM_Triad(STREAM_TYPE scalar)
{
ssize_t j;
#pragma omp parallel for
for (j=0; j<STREAM_ARRAY_SIZE; j++)
a[j] = b[j]+scalar*c[j];
}
/* end of stubs for the "tuned" versions of the kernels */
#endif
四、其他相关知识链接
FIO测试硬盘性能参数和实例总结
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