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/*=========================================================================
*
* Copyright Insight Software Consortium
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0.txt
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
*=========================================================================*/
#include <iostream>
#include "itkFixedArray.h"
#include <time.h>
#include <cstring>
#include <string.h>
int itkFixedArrayTest2(int, char* [] )
{
// Define the number of elements in the array
const unsigned int nelements = 10000000L;
// Define the number of runs used for timing
const unsigned int nrun = 10;
// Declare a simple timer
clock_t t;
typedef itk::FixedArray<double,2> ArrayType;
// Declare an array of nelements FixedArray
// and add a small margin to play with pointers
// but not map outside the allocated memory
ArrayType * vec = new ArrayType[nelements+8];
// Fill it up with zeros
memset(vec,0,(nelements+8)*sizeof(ArrayType));
// Display the alignment of the array
std::cout << "Initial alignment: " << (((size_t)vec)& 7) << "\n";
// Start a simple experiment
t = clock();
double acc1 = 0.0;
for (unsigned int i=0;i<nrun;++i)
{
for (unsigned int j=0;j<nelements;++j)
{
acc1 += vec[j][0];
}
}
// Get the final timing and display it
t=clock() - t;
const double time1 = (t*1000.0) / CLOCKS_PER_SEC;
std::cout << "Initial execution time: "
<< time1 << "ms\n";
// We now force an 8 bytes aligned array
// Cast the pointer to char to play with bytes
char * p = reinterpret_cast<char*>( vec );
// Move the char pointer until it is aligned on 8 bytes
while ( ( (size_t)p ) % 8 )
{
++p;
}
// Cast the 8 bytes aligned pointer back to the original type
ArrayType * vec2 = reinterpret_cast<ArrayType*>( p );
// Make sure the new pointer is well aligned by
// displaying the alignment
std::cout << "New alignment: " << (((size_t)vec2)& 7) << "\n";
// Start the simple experiment on the 8 byte aligned array
t = clock();
double acc2 = 0.0;
for (unsigned int i=0;i<nrun;++i)
{
for (unsigned int j=0;j<nelements;++j)
{
acc2 += vec2[j][0];
}
}
// Get the final timing and display it
t = clock() - t;
const double time2 = (t*1000.0) / CLOCKS_PER_SEC;
std::cout << "Execution time: "
<< time2 << "ms\n";
// Free up the memory
delete[] vec;
const double ratio = 100.0 * ( time1 - time2 ) / time2;
const bool sameptr = (vec==vec2);
if (sameptr) std::cout << "Same pointers: true" <<std::endl;
else std::cout << "Same pointers: false" <<std::endl;
std::cout << "Performance ratio = " << ratio << "%" << std::endl;
if( !sameptr && ratio > 20.0 ) // tolerates only 20%
{
std::cerr << "Performance degraded below tolerance" << std::endl;
return EXIT_FAILURE;
}
// Make sure we do something with the sums otherwise everything
// could be optimized away by the compiler
if( acc1 == 0.0 && acc2 == 0.0 )
{
return EXIT_SUCCESS;
}
return EXIT_FAILURE;
}
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