AD<Base> atan2 (const AD<Base> &y, const AD<Base> &x)
{ AD<Base> alpha;
AD<Base> beta;
AD<Base> theta;
AD<Base> zero(0.);
AD<Base> pi2(2. * atan(1.));
AD<Base> pi(2. * pi2);
AD<Base> ax = abs(x);
AD<Base> ay = abs(y);
// if( ax > ay )
// theta = atan(ay / ax);
// else theta = pi2 - atan(ax / ay);
alpha = atan(ay / ax);
beta = pi2 - atan(ax / ay);
theta = CondExpGt(ax, ay, alpha, beta); // use of CondExp
// if( x <= 0 )
// theta = pi - theta;
theta = CondExpLe(x, zero, pi - theta, theta); // use of CondExp
// if( y <= 0 )
// theta = - theta;
theta = CondExpLe(y, zero, -theta, theta); // use of CondExp
return theta;
}
inline double CondExp(
const double &flag ,
const double &exp_if_true ,
const double &exp_if_false )
{
return CondExpGt(flag, 0., exp_if_true, exp_if_false);
}
inline float CondExp(
const float &flag ,
const float &exp_if_true ,
const float &exp_if_false )
{
return CondExpGt(flag, float(0), exp_if_true, exp_if_false);
}
int LuRatio(SizeVector &ip, SizeVector &jp, ADvector &LU, AD<Base> &ratio) //
{
typedef ADvector FloatVector; //
typedef AD<Base> Float; //
// check numeric type specifications
CheckNumericType<Float>();
// check simple vector class specifications
CheckSimpleVector<Float, FloatVector>();
CheckSimpleVector<size_t, SizeVector>();
size_t i, j; // some temporary indices
const Float zero( 0 ); // the value zero as a Float object
size_t imax; // row index of maximum element
size_t jmax; // column indx of maximum element
Float emax; // maximum absolute value
size_t p; // count pivots
int sign; // sign of the permutation
Float etmp; // temporary element
Float pivot; // pivot element
// -------------------------------------------------------
size_t n = size_t(ip.size());
CPPAD_ASSERT_KNOWN(
size_t(jp.size()) == n,
"Error in LuFactor: jp must have size equal to n"
);
CPPAD_ASSERT_KNOWN(
size_t(LU.size()) == n * n,
"Error in LuFactor: LU must have size equal to n * m"
);
// -------------------------------------------------------
// initialize row and column order in matrix not yet pivoted
for(i = 0; i < n; i++)
{ ip[i] = i;
jp[i] = i;
}
// initialize the sign of the permutation
sign = 1;
// initialize the ratio //
ratio = Float(1); //
// ---------------------------------------------------------
// Reduce the matrix P to L * U using n pivots
for(p = 0; p < n; p++)
{ // determine row and column corresponding to element of
// maximum absolute value in remaining part of P
imax = jmax = n;
emax = zero;
for(i = p; i < n; i++)
{ for(j = p; j < n; j++)
{ CPPAD_ASSERT_UNKNOWN(
(ip[i] < n) & (jp[j] < n)
);
etmp = LU[ ip[i] * n + jp[j] ];
// check if maximum absolute value so far
if( AbsGeq (etmp, emax) )
{ imax = i;
jmax = j;
emax = etmp;
}
}
}
for(i = p; i < n; i++) //
{ for(j = p; j < n; j++) //
{ etmp = abs(LU[ ip[i] * n + jp[j] ] / emax); //
ratio = //
CondExpGt(etmp, ratio, etmp, ratio); //
} //
} //
CPPAD_ASSERT_KNOWN(
(imax < n) & (jmax < n) ,
"AbsGeq must return true when second argument is zero"
);
if( imax != p )
{ // switch rows so max absolute element is in row p
i = ip[p];
ip[p] = ip[imax];
ip[imax] = i;
sign = -sign;
}
if( jmax != p )
{ // switch columns so max absolute element is in column p
j = jp[p];
jp[p] = jp[jmax];
jp[jmax] = j;
sign = -sign;
}
// pivot using the max absolute element
pivot = LU[ ip[p] * n + jp[p] ];
// check for determinant equal to zero
if( pivot == zero )
{ // abort the mission
return 0;
}
// Reduce U by the elementary transformations that maps
// LU( ip[p], jp[p] ) to one. Only need transform elements
// above the diagonal in U and LU( ip[p] , jp[p] ) is
// corresponding value below diagonal in L.
for(j = p+1; j < n; j++)
LU[ ip[p] * n + jp[j] ] /= pivot;
// Reduce U by the elementary transformations that maps
// LU( ip[i], jp[p] ) to zero. Only need transform elements
// above the diagonal in U and LU( ip[i], jp[p] ) is
// corresponding value below diagonal in L.
for(i = p+1; i < n; i++ )
{ etmp = LU[ ip[i] * n + jp[p] ];
for(j = p+1; j < n; j++)
{ LU[ ip[i] * n + jp[j] ] -=
etmp * LU[ ip[p] * n + jp[j] ];
}
}
}
return sign;
}
