miscmaths.cc

	y = x - n;
	n = n - 1;
	psi = csevl(2*y-1, psics, ntpsi);
	if(n==-1)
	  {
	    psi = psi - 1.0/x;
	  }
      }
    else
      {
	const float aux = csevl(8/(Sqr(y))-1, apsics, ntapsi);
	psi = log(x) - 0.5/x + aux;
      }
    
    return psi;
  }

  void glm_vb(const Matrix& X, const ColumnVector& Y, ColumnVector& B, SymmetricMatrix& ilambda_B, int niters)
  {
    // Does Variational Bayes inference on GLM Y=XB+e with ARD priors on B
    // design matrix X should be num_tpts*num_evs

    /////////////////////
    // setup
    OUT("Setup");

    int ntpts=Y.Nrows();
    int nevs=X.Ncols();

    if(ntpts!=X.Nrows())
      throw Exception("COCK");

    OUT(nevs);
    OUT(ntpts);

    ColumnVector gam_m(nevs);
    gam_m=1e10;
    float gam_y;

    ColumnVector lambdaB(nevs);
    if(nevs<ntpts-10)
      {
	// initialise with OLS
	B=pinv(X)*Y;
	ColumnVector res=Y-X*B;
	gam_y=(ntpts-nevs)/(res.t()*res).AsScalar();

	ilambda_B << (X.t()*X*gam_y).i();
	lambdaB=0;
	for(int l=1; l <= nevs; l++)
	  {
	    lambdaB(l)=ilambda_B(l,l);
	  }
      }
    else
      {
	OUT("no ols");
	B.ReSize(nevs);
	B=0;
	lambdaB=1;

// 	ColumnVector res=Y-X*B;
// 	gam_y=ntpts/(res.t()*res).AsScalar();

	gam_y=10;
      }

//     OUT(B(1));
//     OUT(lambdaB(1));

    float trace_ilambdaZZ=1;

    SymmetricMatrix ZZ;
    ZZ << X.t()*X;

    Matrix ZY = X.t()*Y;

    float YY=0;
    for(int t=1; t <= ntpts; t++)
      YY += Sqr(Y(t));

    /////////////////////
    // iterate
    OUT("Iterate");

    int i = 1;;
    for(; i<=niters; i++)
      {
	cout<<i<<",";
	////////////////////
	// update phim
	for(int l=1; l <= nevs; l++)
	  {
	    float b_m0 = 1e10;
	    float c_m0 = 2;

	    float c_m = 1.0/2.0 + c_m0;	    
	    float b_m = 1.0/(0.5*(Sqr(B(l))+lambdaB(l))+1.0/b_m0);
	    gam_m(l) = b_m*c_m;	    
	  }

// 	OUT(gam_m(1));

	////////////////////
	// update B
	ColumnVector beta(nevs);
	beta = 0;
	SymmetricMatrix lambda_B(nevs);
	lambda_B = 0;

	for(int l=1; l <= nevs; l++)
	  lambda_B(l,l)=gam_m(l);

	SymmetricMatrix tmp = lambda_B + gam_y*ZZ;
	lambda_B << tmp;

	beta += gam_y*ZY;

	ilambda_B << lambda_B.i();
	B=ilambda_B*beta;

	lambdaB.ReSize(nevs);
	lambdaB=0;
	for(int l=1; l <= nevs; l++)
	  {
	    lambdaB(l)=ilambda_B(l,l);
	  }
	
	////////////////////
	// compute trace for noise precision phiy update
	
	SymmetricMatrix tmp3;
	tmp3 << ilambda_B;
	
	SymmetricMatrix tmp2;
	tmp2 << tmp3*ZZ;
	
	trace_ilambdaZZ=tmp2.Trace();	
// 	OUT(trace_ilambdaZZ);


	/////////////////////
	// update phiy
	float b_y0 = 1e10;
	float c_y0 = 1;

	float c_y = (ntpts-1)/2.0 + c_y0;

	float sum = YY + (B.t()*ZZ*B).AsScalar() - 2*(B.t()*ZY).AsScalar();
	
	float b_y = 1.0/(0.5*(sum + trace_ilambdaZZ)+1/b_y0);
	
	gam_y = b_y*c_y;

// 	OUT(gam_y);	     

      }

    cout << endl;
  }

vector<float> ColumnVector2vector(const ColumnVector& col)
{
  vector<float> vec(col.Nrows());
  
  for(int c = 0; c < col.Nrows(); c++)
    vec[c] = col(c+1);
  
  return vec;
}

/////////////////////////////////////////////////////////////////////////////////////////////////////

// Uninteresting byte swapping functions

typedef struct { unsigned char a,b ; } TWObytes ;

void Swap_2bytes( int n , void *ar )    /* 2 bytes at a time */
{
  register int ii ;
   register TWObytes *tb = (TWObytes *)ar ;
   register unsigned char tt ;

   for( ii=0 ; ii < n ; ii++ ){
     tt = tb[ii].a ; tb[ii].a = tb[ii].b ; tb[ii].b = tt ;
   }
   return ;
}

/*---------------------------------------------------------------------------*/

typedef struct { unsigned char a,b,c,d ; } FOURbytes ;

void Swap_4bytes( int n , void *ar )    /* 4 bytes at a time */
{
   register int ii ;
   register FOURbytes *tb = (FOURbytes *)ar ;
   register unsigned char tt ;

   for( ii=0 ; ii < n ; ii++ ){
     tt = tb[ii].a ; tb[ii].a = tb[ii].d ; tb[ii].d = tt ;
     tt = tb[ii].b ; tb[ii].b = tb[ii].c ; tb[ii].c = tt ;
   }
   return ;
}

/*---------------------------------------------------------------------------*/

typedef struct { unsigned char a,b,c,d , D,C,B,A ; } EIGHTbytes ;

void Swap_8bytes( int n , void *ar )    /* 8 bytes at a time */
{
   register int ii ;
   register EIGHTbytes *tb = (EIGHTbytes *)ar ;
   register unsigned char tt ;

   for( ii=0 ; ii < n ; ii++ ){
     tt = tb[ii].a ; tb[ii].a = tb[ii].A ; tb[ii].A = tt ;
     tt = tb[ii].b ; tb[ii].b = tb[ii].B ; tb[ii].B = tt ;
     tt = tb[ii].c ; tb[ii].c = tb[ii].C ; tb[ii].C = tt ;
     tt = tb[ii].d ; tb[ii].d = tb[ii].D ; tb[ii].D = tt ;
   }
   return ;
}

/*---------------------------------------------------------------------------*/

typedef struct { unsigned char a,b,c,d,e,f,g,h ,
                               H,G,F,E,D,C,B,A  ; } SIXTEENbytes ;

void Swap_16bytes( int n , void *ar )    /* 16 bytes at a time */
{
   register int ii ;
   register SIXTEENbytes *tb = (SIXTEENbytes *)ar ;
   register unsigned char tt ;

   for( ii=0 ; ii < n ; ii++ ){
     tt = tb[ii].a ; tb[ii].a = tb[ii].A ; tb[ii].A = tt ;
     tt = tb[ii].b ; tb[ii].b = tb[ii].B ; tb[ii].B = tt ;
     tt = tb[ii].c ; tb[ii].c = tb[ii].C ; tb[ii].C = tt ;
     tt = tb[ii].d ; tb[ii].d = tb[ii].D ; tb[ii].D = tt ;

     tt = tb[ii].e ; tb[ii].e = tb[ii].E ; tb[ii].E = tt ;
     tt = tb[ii].f ; tb[ii].f = tb[ii].F ; tb[ii].F = tt ;
     tt = tb[ii].g ; tb[ii].g = tb[ii].G ; tb[ii].G = tt ;
     tt = tb[ii].h ; tb[ii].h = tb[ii].H ; tb[ii].H = tt ;
   }
   return ;
}

/*---------------------------------------------------------------------------*/

void Swap_Nbytes( int n , int siz , void *ar )  /* subsuming case */
{
   switch( siz ){
     case 2:  Swap_2bytes ( n , ar ) ; break ;
     case 4:  Swap_4bytes ( n , ar ) ; break ;
     case 8:  Swap_8bytes ( n , ar ) ; break ;
     case 16: Swap_16bytes( n , ar ) ; break ;
   }
   return ;
}

// end namespace MISCMATHS
}