RichardsFastSlow/src/math/algo.cpp

#include "algo.hpp"

void Thomas(size_t n,double* a,double* b,double* c,double* d,double* x){
  double last=c[0]=c[0]/b[0];
  for(size_t i=1;i<n-1;++i){
    last=c[i]=c[i]/(b[i]-a[i-1]*last);
  }
  last=d[0]=d[0]/b[0];
  for(size_t i=1;i<n;++i){
    last=d[i]=(d[i]-a[i-1]*last)/(b[i]-a[i-1]*c[i-1]);
  }
  last=x[n-1]=d[n-1];
  for(int i=n-1;i>0;--i){
    last=x[i-1]=d[i-1]-c[i-1]*last;
  }
}

double
norm2(double* u,size_t n){
  double r=0;
  for(size_t i=0;i<n;++i){
    double t=u[i];
    r+=(t*t);
  }
  return sqrt(r);
}

double
error2(double* u,double* v,size_t n){
  double r=0;
  for(size_t i=0;i<n;++i){
    double t=u[i]-v[i];
    r+=(t*t);
  }
  return sqrt(r);
}

void
clear(double* u,size_t n){
  for(size_t i=0;i<n;++i){
    u[i]=0;
  }
}

void
display(string name,double* u,size_t n){
  cout<<"------| "<<name<<" |------"<<endl;
  for(size_t i=0;i<n;++i){
    cout<<i<<" : "<<u[i]<<endl;
  }
  cout<<"--------------------------"<<endl;
}