void Bio_test(){
 double mu0=1.256637062*1E-6;
 double x[256*40],y[256*40],z[256*40];
 double Hx[100],Hy[100],Hz[100];
 double xm[100],ym[100],zm[100];
 int nm=2;
 int jn=256*40;
 double cir_R=10;//[m]
 double I=2;//[A]
 double pi=TMath::Pi();

 TPolyMarker3D *check;
  check=new TPolyMarker3D(256);
 TPolyLine3D *checkCoil;
  checkCoil=new TPolyLine3D(256);

 for(int i=0;i<nm*1;++i){
    xm[i]=0;
    ym[i]=0;
    zm[i]=0+20*i/(double)nm;
      check->SetPoint(i,xm[i],ym[i],zm[i]);
 }
 for(int j=0;j<jn;++j){
    double theta=2*pi*j/(double)jn;
    x[j]=cir_R*cos(theta);
    y[j]=cir_R*sin(theta);
    z[j]=0;
      checkCoil->SetPoint(j,x[j],y[j],z[j]);
 }
 for(int i=0;i<nm;++i){

     Hx[i]=0; Hy[i]=0; Hz[i]=0;
    for(int j=0;j<(jn-1);++j){
      double ds[3];
      double rr[3];
      double dHx,dHy,dHz;

      ds[0]=x[j+1]-x[j];
      ds[1]=y[j+1]-y[j];
      ds[2]=z[j+1]-z[j];
      rr[0]=xm[i]-x[j];
      rr[1]=ym[i]-y[j];
      rr[2]=zm[i]-z[j];
//      printf("x=%e y=%e z=%e\n",x[j],y[j],z[j]);//getchar();
//      printf("ds=%e ds=%e ds=%e\n",ds[0],ds[1],ds[2]);//getchar();

      double rr0=sqrt(rr[0]*rr[0]+rr[1]*rr[1]+rr[2]*rr[2]);
      dHx=I*(ds[1]*rr[2]-ds[2]*rr[1])/(double)pow(rr0,3);
      dHy=I*(ds[2]*rr[0]-ds[0]*rr[2])/(double)pow(rr0,3);
      dHz=I*(ds[0]*rr[1]-ds[1]*rr[0])/(double)pow(rr0,3);
//      printf("dHx=%e dHy=%e dHz=%e\n",dHx,dHy,dHz);getchar();
      Hx[i]=Hx[i]+dHx;
      Hy[i]=Hy[i]+dHy;
      Hz[i]=Hz[i]+dHz;
    }
    Hx[i]=mu0*Hx[i]/(double)(4*pi);
    Hy[i]=mu0*Hy[i]/(double)(4*pi);
    Hz[i]=mu0*Hz[i]/(double)(4*pi);
    printf("point at %d x=%lf y=%lf z=%lf Bx=%e By=%e Bz=%e\n",i,xm[i],ym[i],zm[i],Hx[i],Hy[i],Hz[i]);
   } 
//H=I/2r   circle
//H=I/2pir  line 

    double B_test=mu0*I/(double)(2*cir_R);
    printf("B_check=%e\n",B_test);

///////Graph
gROOT->SetStyle("Plain");
gROOT->ForceStyle();
gStyle->SetOptStat(0);
gStyle->SetCanvasBorderMode(0);
gStyle->SetPadColor(0);
gStyle->SetTitleFillColor(0);
gStyle->SetStatColor(0);
//
 gStyle->SetCanvasBorderMode(0);//remove yellow line
 gStyle->SetCanvasColor(0);
 gStyle->SetFrameLineColor(1);
 gStyle->SetPadColor(0);
 gStyle->SetTitleFillColor(0);
 gStyle->SetStatColor(0);
 TCanvas *c2 = new TCanvas("c2","coil",200,100,1000,700);
 TH3F *framecc2;
   framecc2 = new TH3F("framecc2","",10, -10, 10,10, -10, 10, 10,-10,10);
         framecc2->GetXaxis()->SetLabelSize(0.04);
         framecc2->GetXaxis()->SetTitleSize(0.04);
         framecc2->GetYaxis()->SetLabelSize(0.04);
         framecc2->GetYaxis()->SetTitleSize(0.04);
         framecc2->GetZaxis()->SetLabelSize(0.04);
         framecc2->GetZaxis()->SetTitleSize(0.04);
         framecc2->GetXaxis()->SetTitle("x [m]");
         framecc2->GetYaxis()->SetTitle("y [m]");
         framecc2->GetZaxis()->SetTitle("z [m]");
         framecc2->GetXaxis()->SetTitleOffset(1.2);
         framecc2->GetYaxis()->SetTitleOffset(1.2);
         framecc2->GetZaxis()->SetTitleOffset(1.6);
              framecc2->SetStats(0);
              framecc2->Draw();

    c2->SetLeftMargin(0.15);
    c2->SetRightMargin(0.05);
    c2->SetBottomMargin(0.10);

   check->SetMarkerStyle(24);
   check->SetMarkerColor(2);
   check->Draw("p");
   checkCoil->SetLineColor(6);
   checkCoil->Draw("l");
   //
}