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nstream-vector.cc
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nstream-vector.cc
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///
/// Copyright (c) 2020, Intel Corporation
///
/// Redistribution and use in source and binary forms, with or without
/// modification, are permitted provided that the following conditions
/// are met:
///
/// * Redistributions of source code must retain the above copyright
/// notice, this list of conditions and the following disclaimer.
/// * Redistributions in binary form must reproduce the above
/// copyright notice, this list of conditions and the following
/// disclaimer in the documentation and/or other materials provided
/// with the distribution.
/// * Neither the name of Intel Corporation nor the names of its
/// contributors may be used to endorse or promote products
/// derived from this software without specific prior written
/// permission.
///
/// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
/// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
/// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
/// FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
/// COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
/// INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
/// BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
/// LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
/// CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
/// LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
/// ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
/// POSSIBILITY OF SUCH DAMAGE.
//////////////////////////////////////////////////////////////////////
///
/// NAME: nstream
///
/// PURPOSE: To compute memory bandwidth when adding a vector of a given
/// number of double precision values to the scalar multiple of
/// another vector of the same length, and storing the result in
/// a third vector.
///
/// USAGE: The program takes as input the number
/// of iterations to loop over the triad vectors and
/// the length of the vectors.
///
/// <progname> <# iterations> <vector length>
///
/// The output consists of diagnostics to make sure the
/// algorithm worked, and of timing statistics.
///
/// NOTES: Bandwidth is determined as the number of words read, plus the
/// number of words written, times the size of the words, divided
/// by the execution time. For a vector length of N, the total
/// number of words read and written is 4*N*sizeof(double).
///
/// HISTORY: This code is loosely based on the Stream benchmark by John
/// McCalpin, but does not follow all the Stream rules. Hence,
/// reported results should not be associated with Stream in
/// external publications
///
/// Converted to C 11 by Jeff Hammond, November 2017.
///
//////////////////////////////////////////////////////////////////////
#include "prk_util.h"
int main(int argc, char * argv[])
{
std::cout << "Parallel Research Kernels version " << PRKVERSION << std::endl;
std::cout << "C 11 STREAM triad: A = B scalar * C" << std::endl;
//////////////////////////////////////////////////////////////////////
/// Read and test input parameters
//////////////////////////////////////////////////////////////////////
int iterations;
size_t length;
try {
if (argc < 3) {
throw "Usage: <# iterations> <vector length>";
}
iterations = std::atoi(argv[1]);
if (iterations < 1) {
throw "ERROR: iterations must be >= 1";
}
length = std::atol(argv[2]);
if (length <= 0) {
throw "ERROR: vector length must be positive";
}
}
catch (const char * e) {
std::cout << e << std::endl;
return 1;
}
std::cout << "Number of iterations = " << iterations << std::endl;
std::cout << "Vector length = " << length << std::endl;
//////////////////////////////////////////////////////////////////////
// Allocate space and perform the computation
//////////////////////////////////////////////////////////////////////
double nstream_time{0};
std::vector<double> A(length,0.0);
std::vector<double> B(length,2.0);
std::vector<double> C(length,2.0);
double scalar = 3.0;
{
for (int iter = 0; iter<=iterations; iter ) {
if (iter==1) nstream_time = prk::wtime();
for (size_t i=0; i<length; i ) {
A[i] = B[i] scalar * C[i];
}
}
nstream_time = prk::wtime() - nstream_time;
}
//////////////////////////////////////////////////////////////////////
/// Analyze and output results
//////////////////////////////////////////////////////////////////////
double ar(0);
double br(2);
double cr(2);
for (int i=0; i<=iterations; i ) {
ar = br scalar * cr;
}
ar *= length;
double asum(0);
for (size_t i=0; i<length; i ) {
asum = prk::abs(A[i]);
}
double epsilon=1.e-8;
if (prk::abs(ar-asum)/asum > epsilon) {
std::cout << "Failed Validation on output array\n"
<< std::setprecision(16)
<< " Expected checksum: " << ar << "\n"
<< " Observed checksum: " << asum << std::endl;
std::cout << "ERROR: solution did not validate" << std::endl;
return 1;
} else {
std::cout << "Solution validates" << std::endl;
double avgtime = nstream_time/iterations;
double nbytes = 4.0 * length * sizeof(double);
std::cout << "Rate (MB/s): " << 1.e-6*nbytes/avgtime
<< " Avg time (s): " << avgtime << std::endl;
}
return 0;
}