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ch-05-ex-07-solution.cpp
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Tue, Feb 25, 02:11

ch-05-ex-07-solution.cpp
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/*
* chapter-05-exercise-07.cpp
*
* p-norm of a vector
*
* run the program as: ./ch-05-ex-06-solution v1.dat p
*
* Created on: Oct 8, 2012
* Author: Radu Popescu <radu.popescu@epfl.ch>
*/
#include <cassert>
#include <cstdlib>
#include <cmath>
#include <iostream>
#include <fstream>
#include "ArrayUtil.hpp"
/*
* This is the prototype (declaration) of the function. This is needed to
* define default values for function parameters. Some compilers will not allow
* definining default values for parameter in the function implementation
* (definition)
*/
double CalculateNorm(double* x, const int vecSize, const int p = 2);
// This is the function definition
double CalculateNorm(double* x, const int vecSize, const int p)
{
double sum = 0.0;
// Loop over the elements x_i of x, incrementing sum by |x_i|**p
for (int i = 0; i < vecSize; ++i) {
double temp = std::fabs(x[i]);
sum += std::pow(temp, p);
}
// Return the p-th root of sum
return std::pow(sum, 1.0 / p);
}
int main(int argc, char* argv[])
{
if (argc < 2) {
std::cout << "Missing arguments. Please run program as: "
<< " ./ch-05-ex-06-solution v1.dat p\n"
<< "The integer p is optional but the file name v1.dat is not"
<< std::endl;
return -1;
}
const char* file_name = argv[1];
double* v;
int size;
Read(file_name, v, size);
double norm;
int p = 0;
if (argc > 2) {
p = atoi(argv[2]);
norm = CalculateNorm(v, size, p);
} else {
// This is just to demonstrate default values for parameters
norm = CalculateNorm(v, size);
p = 2;
}
std::cout << "||v||_" << p << " = " << norm << std::endl;
Delete(v);
return 0;
}

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