static double interp_cubic(double f0, double fp0, double f1, double fp1, double zl, double zh)
{
double eta = 3 * (f1 - f0) - 2 * fp0 - fp1;
double xi = fp0 + fp1 - 2 * (f1 - f0);
double c0 = f0, c1 = fp0, c2 = eta, c3 = xi;
double zmin, fminn;
double z0, z1;
zmin = zl;
fminn = cubic(c0, c1, c2, c3, zl);
check_extremum(c0, c1, c2, c3, zh, &zmin, &fminn);
{
int n = gsl_poly_solve_quadratic(3 * c3, 2 * c2, c1, &z0, &z1);
if (n == 2) { /* found 2 roots */
if (z0 > zl && z0 < zh)
check_extremum(c0, c1, c2, c3, z0, &zmin, &fminn);
if (z1 > zl && z1 < zh)
check_extremum(c0, c1, c2, c3, z1, &zmin, &fminn);
} else if (n == 1) { /* found 1 root */
if (z0 > zl && z0 < zh)
check_extremum(c0, c1, c2, c3, z0, &zmin, &fminn);
}
}
return zmin;
}
int Polinomio::getRaicesCuadradas(double &x1, double &x2) {
// Nos aseguramos que efectivamente sea un polinomio cuadrático.
assert(this != 0 && this->getGrado()>=2 && (*this)[2] != 0);
if(this->getGrado() > 2) {
for(int i=3; i<=this->getGrado(); i++) {
assert((*this)[i] == 0);
}
}
int num = gsl_poly_solve_quadratic((*this)[2],(*this)[1],(*this)[0],&x1,&x2);
return num;
}
pure_expr* wrap_gsl_poly_solve_quadratic(double a, double b, double c)
{
double x0, x1;
switch (gsl_poly_solve_quadratic(a, b, c, &x0, &x1)) {
case 0: return pure_listl(0);
case 1: return pure_listl(1, pure_double(x0));
case 2: return pure_listl(2, pure_double(x0), pure_double(x1));
default: return NULL;
}
}
int
m_bez_plan_intersection (vector A, vector B, vector C, vector O, vector N,
double *t1, double *t2)
{
double va, vb, vc, vo, a, b, c;
va = DotProd (A, N);
vb = DotProd (B, N);
vc = DotProd (C, N);
vo = DotProd (O, N);
a = va - 2. * vb + vc;
b = 2. * (vb - va);
c = va - vo;
return gsl_poly_solve_quadratic (a, b, c, t1, t2);
}
int
lv_bez_lin_inters (LinVec A, LinVec B, LinVec C, LinVec la, LinVec lb,
double *t1, double *t2)
{
double va, vb, vc, vo, a, b, c;
LinVec N;
N = lv_arb_per (lv_ineq (la, lb));
va = lv_prod (A, N);
vb = lv_prod (B, N);
vc = lv_prod (C, N);
vo = lv_prod (la, N);
a = va - 2. * vb + vc;
b = 2. * (vb - va);
c = va - vo;
return gsl_poly_solve_quadratic (a, b, c, t1, t2);
}
CAMLprim value ml_gsl_poly_solve_quadratic(value a, value b, value c)
{
double x0, x1;
int n ;
n = gsl_poly_solve_quadratic(Double_val(a), Double_val(b),
Double_val(c), &x0, &x1);
{
CAMLparam0();
CAMLlocal1(r);
if(n == 0)
r = Val_int(0);
else {
r = alloc(2, 0);
Store_field(r, 0, copy_double(x0));
Store_field(r, 1, copy_double(x1));
} ;
CAMLreturn(r);
}
}
/**
@brief This function finds the real roots of the quadratic equation,
\f$a x^2 + b x + c = 0\f$
The number of real roots (either zero, one or two) is returned, and
their locations are stored in @a x0 and @a x1. If no real roots are found
then @a x0 and @a x1 are not modified. If one real root is found (i.e. if
a=0) then it is stored in @a x0. When two real roots are found they
are stored in @a x0 and @a x1 in ascending order. The case of coincident
roots is not considered special. For example \f$(x-1)^2=0\f$ will have
two roots, which happen to have exactly equal values.
The number of roots found depends on the sign of the discriminant
\f$b^2 - 4 a c\f$. This will be subject to rounding and
cancellation errors when computed in double precision, and will
also be subject to errors if the coefficients of the polynomial are
inexact. These errors may cause a discrete change in the number of
roots. However, for polynomials with small integer coefficients the
discriminant can always be computed exactly.
@param[in] a
@param[in] b
@param[in] c
@param[out] x0 root value 1 (if found)
@param[out] x1 root value 2 (if found)
*/
int QGSLPolynomials :: solveQuadratic (double a, double b, double c, double &x0, double &x1)
{
return gsl_poly_solve_quadratic(a, b, c, &x0, &x1);
}
int
main (void)
{
const double eps = 100.0 * GSL_DBL_EPSILON;
gsl_ieee_env_setup ();
/* Polynomial evaluation */
{
double x, y;
double c[3] = { 1.0, 0.5, 0.3 };
x = 0.5;
y = gsl_poly_eval (c, 3, x);
gsl_test_rel (y, 1 + 0.5 * x + 0.3 * x * x, eps,
"gsl_poly_eval({1, 0.5, 0.3}, 0.5)");
}
{
double x, y;
double d[11] = { 1, -1, 1, -1, 1, -1, 1, -1, 1, -1, 1 };
x = 1.0;
y = gsl_poly_eval (d, 11, x);
gsl_test_rel (y, 1.0, eps,
"gsl_poly_eval({1,-1, 1, -1, 1, -1, 1, -1, 1, -1, 1}, 1.0)");
}
{
gsl_complex x, y;
double c[1] = {0.3};
GSL_SET_REAL (&x, 0.75);
GSL_SET_IMAG (&x, 1.2);
y = gsl_poly_complex_eval (c, 1, x);
gsl_test_rel (GSL_REAL (y), 0.3, eps, "y.real, gsl_poly_complex_eval ({0.3}, 0.75 + 1.2i)");
gsl_test_rel (GSL_IMAG (y), 0.0, eps, "y.imag, gsl_poly_complex_eval ({0.3}, 0.75 + 1.2i)");
}
{
gsl_complex x, y;
double c[4] = {2.1, -1.34, 0.76, 0.45};
GSL_SET_REAL (&x, 0.49);
GSL_SET_IMAG (&x, 0.95);
y = gsl_poly_complex_eval (c, 4, x);
gsl_test_rel (GSL_REAL (y), 0.3959143, eps, "y.real, gsl_poly_complex_eval ({2.1, -1.34, 0.76, 0.45}, 0.49 + 0.95i)");
gsl_test_rel (GSL_IMAG (y), -0.6433305, eps, "y.imag, gsl_poly_complex_eval ({2.1, -1.34, 0.76, 0.45}, 0.49 + 0.95i)");
}
{
gsl_complex x, y;
gsl_complex c[1];
GSL_SET_REAL (&c[0], 0.674);
GSL_SET_IMAG (&c[0], -1.423);
GSL_SET_REAL (&x, -1.44);
GSL_SET_IMAG (&x, 9.55);
y = gsl_complex_poly_complex_eval (c, 1, x);
gsl_test_rel (GSL_REAL (y), 0.674, eps, "y.real, gsl_complex_poly_complex_eval ({0.674 - 1.423i}, -1.44 + 9.55i)");
gsl_test_rel (GSL_IMAG (y), -1.423, eps, "y.imag, gsl_complex_poly_complex_eval ({0.674 - 1.423i}, -1.44 + 9.55i)");
}
{
gsl_complex x, y;
gsl_complex c[4];
GSL_SET_REAL (&c[0], -2.31);
GSL_SET_IMAG (&c[0], 0.44);
GSL_SET_REAL (&c[1], 4.21);
GSL_SET_IMAG (&c[1], -3.19);
GSL_SET_REAL (&c[2], 0.93);
GSL_SET_IMAG (&c[2], 1.04);
GSL_SET_REAL (&c[3], -0.42);
GSL_SET_IMAG (&c[3], 0.68);
GSL_SET_REAL (&x, 0.49);
GSL_SET_IMAG (&x, 0.95);
y = gsl_complex_poly_complex_eval (c, 4, x);
gsl_test_rel (GSL_REAL (y), 1.82462012, eps, "y.real, gsl_complex_poly_complex_eval ({-2.31 + 0.44i, 4.21 - 3.19i, 0.93 + 1.04i, -0.42 + 0.68i}, 0.49 + 0.95i)");
gsl_test_rel (GSL_IMAG (y), 2.30389412, eps, "y.imag, gsl_complex_poly_complex_eval ({-2.31 + 0.44i, 4.21 - 3.19i, 0.93 + 1.04i, -0.42 + 0.68i}, 0.49 + 0.95i)");
}
/* Quadratic */
{
double x0, x1;
int n = gsl_poly_solve_quadratic (4.0, -20.0, 26.0, &x0, &x1);
gsl_test (n != 0, "gsl_poly_solve_quadratic, no roots, (2x - 5)^2 = -1");
}
{
double x0, x1;
int n = gsl_poly_solve_quadratic (4.0, -20.0, 25.0, &x0, &x1);
gsl_test (n != 2, "gsl_poly_solve_quadratic, one root, (2x - 5)^2 = 0");
gsl_test_rel (x0, 2.5, 1e-9, "x0, (2x - 5)^2 = 0");
gsl_test_rel (x1, 2.5, 1e-9, "x1, (2x - 5)^2 = 0");
gsl_test (x0 != x1, "x0 == x1, (2x - 5)^2 = 0");
}
{
double x0, x1;
int n = gsl_poly_solve_quadratic (4.0, -20.0, 21.0, &x0, &x1);
gsl_test (n != 2, "gsl_poly_solve_quadratic, two roots, (2x - 5)^2 = 4");
gsl_test_rel (x0, 1.5, 1e-9, "x0, (2x - 5)^2 = 4");
gsl_test_rel (x1, 3.5, 1e-9, "x1, (2x - 5)^2 = 4");
}
{
double x0, x1;
int n = gsl_poly_solve_quadratic (4.0, 7.0, 0.0, &x0, &x1);
gsl_test (n != 2, "gsl_poly_solve_quadratic, two roots, x(4x + 7) = 0");
gsl_test_rel (x0, -1.75, 1e-9, "x0, x(4x + 7) = 0");
gsl_test_rel (x1, 0.0, 1e-9, "x1, x(4x + 7) = 0");
}
{
double x0, x1;
int n = gsl_poly_solve_quadratic (5.0, 0.0, -20.0, &x0, &x1);
gsl_test (n != 2,
"gsl_poly_solve_quadratic, two roots b = 0, 5 x^2 = 20");
gsl_test_rel (x0, -2.0, 1e-9, "x0, 5 x^2 = 20");
gsl_test_rel (x1, 2.0, 1e-9, "x1, 5 x^2 = 20");
}
{
double x0, x1;
int n = gsl_poly_solve_quadratic (0.0, 3.0, -21.0, &x0, &x1);
gsl_test (n != 1,
"gsl_poly_solve_quadratic, one root (linear) 3 x - 21 = 0");
gsl_test_rel (x0, 7.0, 1e-9, "x0, 3x - 21 = 0");
}
{
double x0, x1;
int n = gsl_poly_solve_quadratic (0.0, 0.0, 1.0, &x0, &x1);
gsl_test (n != 0,
"gsl_poly_solve_quadratic, no roots 1 = 0");
}
/* Cubic */
{
double x0, x1, x2;
int n = gsl_poly_solve_cubic (0.0, 0.0, -27.0, &x0, &x1, &x2);
gsl_test (n != 1, "gsl_poly_solve_cubic, one root, x^3 = 27");
gsl_test_rel (x0, 3.0, 1e-9, "x0, x^3 = 27");
}
{
double x0, x1, x2;
int n = gsl_poly_solve_cubic (-51.0, 867.0, -4913.0, &x0, &x1, &x2);
gsl_test (n != 3, "gsl_poly_solve_cubic, three roots, (x-17)^3=0");
gsl_test_rel (x0, 17.0, 1e-9, "x0, (x-17)^3=0");
gsl_test_rel (x1, 17.0, 1e-9, "x1, (x-17)^3=0");
gsl_test_rel (x2, 17.0, 1e-9, "x2, (x-17)^3=0");
}
{
double x0, x1, x2;
int n = gsl_poly_solve_cubic (-57.0, 1071.0, -6647.0, &x0, &x1, &x2);
gsl_test (n != 3,
"gsl_poly_solve_cubic, three roots, (x-17)(x-17)(x-23)=0");
gsl_test_rel (x0, 17.0, 1e-9, "x0, (x-17)(x-17)(x-23)=0");
gsl_test_rel (x1, 17.0, 1e-9, "x1, (x-17)(x-17)(x-23)=0");
gsl_test_rel (x2, 23.0, 1e-9, "x2, (x-17)(x-17)(x-23)=0");
}
{
double x0, x1, x2;
int n = gsl_poly_solve_cubic (-11.0, -493.0, +6647.0, &x0, &x1, &x2);
gsl_test (n != 3,
"gsl_poly_solve_cubic, three roots, (x+23)(x-17)(x-17)=0");
gsl_test_rel (x0, -23.0, 1e-9, "x0, (x+23)(x-17)(x-17)=0");
gsl_test_rel (x1, 17.0, 1e-9, "x1, (x+23)(x-17)(x-17)=0");
gsl_test_rel (x2, 17.0, 1e-9, "x2, (x+23)(x-17)(x-17)=0");
}
{
double x0, x1, x2;
int n = gsl_poly_solve_cubic (-143.0, 5087.0, -50065.0, &x0, &x1, &x2);
gsl_test (n != 3,
"gsl_poly_solve_cubic, three roots, (x-17)(x-31)(x-95)=0");
gsl_test_rel (x0, 17.0, 1e-9, "x0, (x-17)(x-31)(x-95)=0");
gsl_test_rel (x1, 31.0, 1e-9, "x1, (x-17)(x-31)(x-95)=0");
gsl_test_rel (x2, 95.0, 1e-9, "x2, (x-17)(x-31)(x-95)=0");
}
{
double x0, x1, x2;
int n = gsl_poly_solve_cubic (-109.0, 803.0, 50065.0, &x0, &x1, &x2);
gsl_test (n != 3,
"gsl_poly_solve_cubic, three roots, (x+17)(x-31)(x-95)=0");
gsl_test_rel (x0, -17.0, 1e-9, "x0, (x+17)(x-31)(x-95)=0");
gsl_test_rel (x1, 31.0, 1e-9, "x1, (x+17)(x-31)(x-95)=0");
gsl_test_rel (x2, 95.0, 1e-9, "x2, (x+17)(x-31)(x-95)=0");
}
/* Quadratic with complex roots */
{
gsl_complex z0, z1;
int n = gsl_poly_complex_solve_quadratic (4.0, -20.0, 26.0, &z0, &z1);
gsl_test (n != 2,
"gsl_poly_complex_solve_quadratic, 2 roots (2x - 5)^2 = -1");
gsl_test_rel (GSL_REAL (z0), 2.5, 1e-9, "z0.real, (2x - 5)^2 = -1");
gsl_test_rel (GSL_IMAG (z0), -0.5, 1e-9, "z0.imag, (2x - 5)^2 = -1");
gsl_test_rel (GSL_REAL (z1), 2.5, 1e-9, "z1.real, (2x - 5)^2 = -1");
gsl_test_rel (GSL_IMAG (z1), 0.5, 1e-9, "z1.imag, (2x - 5)^2 = -1");
}
{
gsl_complex z0, z1;
int n = gsl_poly_complex_solve_quadratic (4.0, -20.0, 25.0, &z0, &z1);
gsl_test (n != 2,
"gsl_poly_complex_solve_quadratic, one root, (2x - 5)^2 = 0");
gsl_test_rel (GSL_REAL (z0), 2.5, 1e-9, "z0.real, (2x - 5)^2 = 0");
gsl_test_rel (GSL_IMAG (z0), 0.0, 1e-9, "z0.imag (2x - 5)^2 = 0");
gsl_test_rel (GSL_REAL (z1), 2.5, 1e-9, "z1.real, (2x - 5)^2 = 0");
gsl_test_rel (GSL_IMAG (z1), 0.0, 1e-9, "z1.imag (2x - 5)^2 = 0");
gsl_test (GSL_REAL (z0) != GSL_REAL (z1),
"z0.real == z1.real, (2x - 5)^2 = 0");
gsl_test (GSL_IMAG (z0) != GSL_IMAG (z1),
"z0.imag == z1.imag, (2x - 5)^2 = 0");
}
{
gsl_complex z0, z1;
int n = gsl_poly_complex_solve_quadratic (4.0, -20.0, 21.0, &z0, &z1);
gsl_test (n != 2,
"gsl_poly_complex_solve_quadratic, two roots, (2x - 5)^2 = 4");
gsl_test_rel (GSL_REAL (z0), 1.5, 1e-9, "z0.real, (2x - 5)^2 = 4");
gsl_test_rel (GSL_IMAG (z0), 0.0, 1e-9, "z0.imag, (2x - 5)^2 = 4");
gsl_test_rel (GSL_REAL (z1), 3.5, 1e-9, "z1.real, (2x - 5)^2 = 4");
gsl_test_rel (GSL_IMAG (z1), 0.0, 1e-9, "z1.imag, (2x - 5)^2 = 4");
}
{
gsl_complex z0, z1;
int n = gsl_poly_complex_solve_quadratic (4.0, 7.0, 0.0, &z0, &z1);
gsl_test (n != 2,
"gsl_poly_complex_solve_quadratic, two roots, x(4x + 7) = 0");
gsl_test_rel (GSL_REAL (z0), -1.75, 1e-9, "z0.real, x(4x + 7) = 0");
gsl_test_rel (GSL_IMAG (z0), 0.0, 1e-9, "z0.imag, x(4x + 7) = 0");
gsl_test_rel (GSL_REAL (z1), 0.0, 1e-9, "z1.real, x(4x + 7) = 0");
gsl_test_rel (GSL_IMAG (z1), 0.0, 1e-9, "z1.imag, x(4x + 7) = 0");
}
{
gsl_complex z0, z1;
int n = gsl_poly_complex_solve_quadratic (5.0, 0.0, -20.0, &z0, &z1);
gsl_test (n != 2,
"gsl_poly_complex_solve_quadratic, two roots b = 0, 5 x^2 = 20");
gsl_test_rel (GSL_REAL (z0), -2.0, 1e-9, "z0.real, 5 x^2 = 20");
gsl_test_rel (GSL_IMAG (z0), 0.0, 1e-9, "z0.imag, 5 x^2 = 20");
gsl_test_rel (GSL_REAL (z1), 2.0, 1e-9, "z1.real, 5 x^2 = 20");
gsl_test_rel (GSL_IMAG (z1), 0.0, 1e-9, "z1.imag, 5 x^2 = 20");
}
{
gsl_complex z0, z1;
int n = gsl_poly_complex_solve_quadratic (5.0, 0.0, 20.0, &z0, &z1);
gsl_test (n != 2,
"gsl_poly_complex_solve_quadratic, two roots b = 0, 5 x^2 = -20");
gsl_test_rel (GSL_REAL (z0), 0.0, 1e-9, "z0.real, 5 x^2 = -20");
gsl_test_rel (GSL_IMAG (z0), -2.0, 1e-9, "z0.imag, 5 x^2 = -20");
gsl_test_rel (GSL_REAL (z1), 0.0, 1e-9, "z1.real, 5 x^2 = -20");
gsl_test_rel (GSL_IMAG (z1), 2.0, 1e-9, "z1.imag, 5 x^2 = -20");
}
{
gsl_complex z0, z1;
int n = gsl_poly_complex_solve_quadratic (0.0, 3.0, -21.0, &z0, &z1);
gsl_test (n != 1,
"gsl_poly_complex_solve_quadratic, one root (linear) 3 x - 21 = 0");
gsl_test_rel (GSL_REAL (z0), 7.0, 1e-9, "z0.real, 3x - 21 = 0");
gsl_test_rel (GSL_IMAG (z0), 0.0, 1e-9, "z0.imag, 3x - 21 = 0");
}
{
gsl_complex z0, z1;
int n = gsl_poly_complex_solve_quadratic (0.0, 0.0, 1.0, &z0, &z1);
gsl_test (n != 0,
"gsl_poly_complex_solve_quadratic, no roots 1 = 0");
}
/* Cubic with complex roots */
{
gsl_complex z0, z1, z2;
int n = gsl_poly_complex_solve_cubic (0.0, 0.0, -27.0, &z0, &z1, &z2);
gsl_test (n != 3, "gsl_poly_complex_solve_cubic, three root, x^3 = 27");
gsl_test_rel (GSL_REAL (z0), -1.5, 1e-9, "z0.real, x^3 = 27");
gsl_test_rel (GSL_IMAG (z0), -1.5 * sqrt (3.0), 1e-9,
"z0.imag, x^3 = 27");
gsl_test_rel (GSL_REAL (z1), -1.5, 1e-9, "z1.real, x^3 = 27");
gsl_test_rel (GSL_IMAG (z1), 1.5 * sqrt (3.0), 1e-9, "z1.imag, x^3 = 27");
gsl_test_rel (GSL_REAL (z2), 3.0, 1e-9, "z2.real, x^3 = 27");
gsl_test_rel (GSL_IMAG (z2), 0.0, 1e-9, "z2.imag, x^3 = 27");
}
{
gsl_complex z0, z1, z2;
int n = gsl_poly_complex_solve_cubic (-1.0, 1.0, 39.0, &z0, &z1, &z2);
gsl_test (n != 3,
"gsl_poly_complex_solve_cubic, three root, (x+3)(x^2-4x+13) = 0");
gsl_test_rel (GSL_REAL (z0), -3.0, 1e-9, "z0.real, (x+3)(x^2+1) = 0");
gsl_test_rel (GSL_IMAG (z0), 0.0, 1e-9, "z0.imag, (x+3)(x^2+1) = 0");
gsl_test_rel (GSL_REAL (z1), 2.0, 1e-9, "z1.real, (x+3)(x^2+1) = 0");
gsl_test_rel (GSL_IMAG (z1), -3.0, 1e-9, "z1.imag, (x+3)(x^2+1) = 0");
gsl_test_rel (GSL_REAL (z2), 2.0, 1e-9, "z2.real, (x+3)(x^2+1) = 0");
gsl_test_rel (GSL_IMAG (z2), 3.0, 1e-9, "z2.imag, (x+3)(x^2+1) = 0");
}
{
gsl_complex z0, z1, z2;
int n =
gsl_poly_complex_solve_cubic (-51.0, 867.0, -4913.0, &z0, &z1, &z2);
gsl_test (n != 3,
"gsl_poly_complex_solve_cubic, three roots, (x-17)^3=0");
gsl_test_rel (GSL_REAL (z0), 17.0, 1e-9, "z0.real, (x-17)^3=0");
gsl_test_rel (GSL_IMAG (z0), 0.0, 1e-9, "z0.imag, (x-17)^3=0");
gsl_test_rel (GSL_REAL (z1), 17.0, 1e-9, "z1.real, (x-17)^3=0");
gsl_test_rel (GSL_IMAG (z1), 0.0, 1e-9, "z1.imag, (x-17)^3=0");
gsl_test_rel (GSL_REAL (z2), 17.0, 1e-9, "z2.real, (x-17)^3=0");
gsl_test_rel (GSL_IMAG (z2), 0.0, 1e-9, "z2.imag, (x-17)^3=0");
}
{
gsl_complex z0, z1, z2;
int n =
gsl_poly_complex_solve_cubic (-57.0, 1071.0, -6647.0, &z0, &z1, &z2);
gsl_test (n != 3,
"gsl_poly_complex_solve_cubic, three roots, (x-17)(x-17)(x-23)=0");
gsl_test_rel (GSL_REAL (z0), 17.0, 1e-9, "z0.real, (x-17)(x-17)(x-23)=0");
gsl_test_rel (GSL_IMAG (z0), 0.0, 1e-9, "z0.imag, (x-17)(x-17)(x-23)=0");
gsl_test_rel (GSL_REAL (z1), 17.0, 1e-9, "z1.real, (x-17)(x-17)(x-23)=0");
gsl_test_rel (GSL_IMAG (z1), 0.0, 1e-9, "z1.imag, (x-17)(x-17)(x-23)=0");
gsl_test_rel (GSL_REAL (z2), 23.0, 1e-9, "z2.real, (x-17)(x-17)(x-23)=0");
gsl_test_rel (GSL_IMAG (z2), 0.0, 1e-9, "z2.imag, (x-17)(x-17)(x-23)=0");
}
{
gsl_complex z0, z1, z2;
int n =
gsl_poly_complex_solve_cubic (-11.0, -493.0, +6647.0, &z0, &z1, &z2);
gsl_test (n != 3,
"gsl_poly_complex_solve_cubic, three roots, (x+23)(x-17)(x-17)=0");
gsl_test_rel (GSL_REAL (z0), -23.0, 1e-9,
"z0.real, (x+23)(x-17)(x-17)=0");
gsl_test_rel (GSL_IMAG (z0), 0.0, 1e-9, "z0.imag, (x+23)(x-17)(x-17)=0");
gsl_test_rel (GSL_REAL (z1), 17.0, 1e-9, "z1.real, (x+23)(x-17)(x-17)=0");
gsl_test_rel (GSL_IMAG (z1), 0.0, 1e-9, "z1.imag, (x+23)(x-17)(x-17)=0");
gsl_test_rel (GSL_REAL (z2), 17.0, 1e-9, "z2.real, (x+23)(x-17)(x-17)=0");
gsl_test_rel (GSL_IMAG (z2), 0.0, 1e-9, "z2.imag, (x+23)(x-17)(x-17)=0");
}
{
gsl_complex z0, z1, z2;
int n =
gsl_poly_complex_solve_cubic (-143.0, 5087.0, -50065.0, &z0, &z1, &z2);
gsl_test (n != 3,
"gsl_poly_complex_solve_cubic, three roots, (x-17)(x-31)(x-95)=0");
gsl_test_rel (GSL_REAL (z0), 17.0, 1e-9, "z0.real, (x-17)(x-31)(x-95)=0");
gsl_test_rel (GSL_IMAG (z0), 0.0, 1e-9, "z0.imag, (x-17)(x-31)(x-95)=0");
gsl_test_rel (GSL_REAL (z1), 31.0, 1e-9, "z1.real, (x-17)(x-31)(x-95)=0");
gsl_test_rel (GSL_IMAG (z1), 0.0, 1e-9, "z1.imag, (x-17)(x-31)(x-95)=0");
gsl_test_rel (GSL_REAL (z2), 95.0, 1e-9, "z2.real, (x-17)(x-31)(x-95)=0");
gsl_test_rel (GSL_IMAG (z2), 0.0, 1e-9, "z2.imag, (x-17)(x-31)(x-95)=0");
}
{
/* Wilkinson polynomial: y = (x-1)(x-2)(x-3)(x-4)(x-5) */
double a[6] = { -120, 274, -225, 85, -15, 1 };
double z[6*2];
gsl_poly_complex_workspace *w = gsl_poly_complex_workspace_alloc (6);
int status = gsl_poly_complex_solve (a, 6, w, z);
gsl_poly_complex_workspace_free (w);
gsl_test (status,
"gsl_poly_complex_solve, 5th-order Wilkinson polynomial");
gsl_test_rel (z[0], 1.0, 1e-9, "z0.real, 5th-order polynomial");
gsl_test_rel (z[1], 0.0, 1e-9, "z0.imag, 5th-order polynomial");
gsl_test_rel (z[2], 2.0, 1e-9, "z1.real, 5th-order polynomial");
gsl_test_rel (z[3], 0.0, 1e-9, "z1.imag, 5th-order polynomial");
gsl_test_rel (z[4], 3.0, 1e-9, "z2.real, 5th-order polynomial");
gsl_test_rel (z[5], 0.0, 1e-9, "z2.imag, 5th-order polynomial");
gsl_test_rel (z[6], 4.0, 1e-9, "z3.real, 5th-order polynomial");
gsl_test_rel (z[7], 0.0, 1e-9, "z3.imag, 5th-order polynomial");
gsl_test_rel (z[8], 5.0, 1e-9, "z4.real, 5th-order polynomial");
gsl_test_rel (z[9], 0.0, 1e-9, "z4.imag, 5th-order polynomial");
}
{
/* : 8-th order polynomial y = x^8 + x^4 + 1 */
double a[9] = { 1, 0, 0, 0, 1, 0, 0, 0, 1 };
double z[8*2];
double C = 0.5;
double S = sqrt (3.0) / 2.0;
gsl_poly_complex_workspace *w = gsl_poly_complex_workspace_alloc (9);
int status = gsl_poly_complex_solve (a, 9, w, z);
gsl_poly_complex_workspace_free (w);
gsl_test (status, "gsl_poly_complex_solve, 8th-order polynomial");
gsl_test_rel (z[0], -S, 1e-9, "z0.real, 8th-order polynomial");
gsl_test_rel (z[1], C, 1e-9, "z0.imag, 8th-order polynomial");
gsl_test_rel (z[2], -S, 1e-9, "z1.real, 8th-order polynomial");
gsl_test_rel (z[3], -C, 1e-9, "z1.imag, 8th-order polynomial");
gsl_test_rel (z[4], -C, 1e-9, "z2.real, 8th-order polynomial");
gsl_test_rel (z[5], S, 1e-9, "z2.imag, 8th-order polynomial");
gsl_test_rel (z[6], -C, 1e-9, "z3.real, 8th-order polynomial");
gsl_test_rel (z[7], -S, 1e-9, "z3.imag, 8th-order polynomial");
gsl_test_rel (z[8], C, 1e-9, "z4.real, 8th-order polynomial");
gsl_test_rel (z[9], S, 1e-9, "z4.imag, 8th-order polynomial");
gsl_test_rel (z[10], C, 1e-9, "z5.real, 8th-order polynomial");
gsl_test_rel (z[11], -S, 1e-9, "z5.imag, 8th-order polynomial");
gsl_test_rel (z[12], S, 1e-9, "z6.real, 8th-order polynomial");
gsl_test_rel (z[13], C, 1e-9, "z6.imag, 8th-order polynomial");
gsl_test_rel (z[14], S, 1e-9, "z7.real, 8th-order polynomial");
gsl_test_rel (z[15], -C, 1e-9, "z7.imag, 8th-order polynomial");
}
{
int i;
double xa[7] = {0.16, 0.97, 1.94, 2.74, 3.58, 3.73, 4.70 };
double ya[7] = {0.73, 1.11, 1.49, 1.84, 2.30, 2.41, 3.07 };
double dd_expected[7] = { 7.30000000000000e-01,
4.69135802469136e-01,
-4.34737219941284e-02,
2.68681098870099e-02,
-3.22937056934996e-03,
6.12763259971375e-03,
-6.45402453527083e-03 };
double dd[7], coeff[7], work[7];
gsl_poly_dd_init (dd, xa, ya, 7);
for (i = 0; i < 7; i++)
{
gsl_test_rel (dd[i], dd_expected[i], 1e-10, "divided difference dd[%d]", i);
}
for (i = 0; i < 7; i++)
{
double y = gsl_poly_dd_eval(dd, xa, 7, xa[i]);
gsl_test_rel (y, ya[i], 1e-10, "divided difference y[%d]", i);
}
gsl_poly_dd_taylor (coeff, 1.5, dd, xa, 7, work);
for (i = 0; i < 7; i++)
{
double y = gsl_poly_eval(coeff, 7, xa[i] - 1.5);
gsl_test_rel (y, ya[i], 1e-10, "taylor expansion about 1.5 y[%d]", i);
}
}
{
double c[6] = { +1.0, -2.0, +3.0, -4.0, +5.0, -6.0 };
double dc[6];
double x;
x = -0.5;
gsl_poly_eval_derivs(c, 6, x, dc, 6);
gsl_test_rel (dc[0], c[0] + c[1]*x + c[2]*x*x + c[3]*x*x*x + c[4]*x*x*x*x + c[5]*x*x*x*x*x , eps, "gsl_poly_eval_dp({+1, -2, +3, -4, +5, -6}, 3.75)");
gsl_test_rel (dc[1], c[1] + 2.0*c[2]*x + 3.0*c[3]*x*x + 4.0*c[4]*x*x*x + 5.0*c[5]*x*x*x*x , eps, "gsl_poly_eval_dp({+1, -2, +3, -4, +5, -6} deriv 1, -12.375)");
gsl_test_rel (dc[2], 2.0*c[2] + 3.0*2.0*c[3]*x + 4.0*3.0*c[4]*x*x + 5.0*4.0*c[5]*x*x*x , eps, "gsl_poly_eval_dp({+1, -2, +3, -4, +5, -6} deriv 2, +48.0)");
gsl_test_rel (dc[3], 3.0*2.0*c[3] + 4.0*3.0*2.0*c[4]*x + 5.0*4.0*3.0*c[5]*x*x , eps,"gsl_poly_eval_dp({+1, -2, +3, -4, +5, -6} deriv 3, -174.0)");
gsl_test_rel (dc[4], 4.0*3.0*2.0*c[4] + 5.0*4.0*3.0*2.0*c[5]*x, eps, "gsl_poly_eval_dp({+1, -2, +3, -4, +5, -6} deriv 4, +480.0)");
gsl_test_rel (dc[5], 5.0*4.0*3.0*2.0*c[5] , eps, "gsl_poly_eval_dp({+1, -2, +3, -4, +5, -6} deriv 5, -720.0)");
}
/* now summarize the results */
exit (gsl_test_summary ());
}
int gsl_poly_solve_cubic(double k, double a, double b, double c, double *x0, double *x1, double *x2)
{
if (k == 0)
{ // quadratic case
return gsl_poly_solve_quadratic(a, b, c, x0, x1);
}
// normalize
a /= k;
b /= k;
c /= k;
double q = (a * a - 3 * b);
double r = (2 * a * a * a - 9 * a * b + 27 * c);
double Q = q / 9;
double R = r / 54;
double Q3 = Q * Q * Q;
double R2 = R * R;
double CR2 = 729 * r * r;
double CQ3 = 2916 * q * q * q;
if (R == 0 && Q == 0)
{
*x0 = -a / 3;
*x1 = -a / 3;
*x2 = -a / 3;
return 3;
}
else if (CR2 == CQ3)
{
/* this test is actually R2 == Q3, written in a form suitable
for exact computation with integers */
/* Due to finite precision some double roots may be missed, and
considered to be a pair of complex roots z = x +/- epsilon i
close to the real axis. */
double sqrtQ = sqrt(Q);
if (R > 0)
{
*x0 = -2 * sqrtQ - a / 3;
*x1 = sqrtQ - a / 3;
*x2 = sqrtQ - a / 3;
}
else
{
*x0 = -sqrtQ - a / 3;
*x1 = -sqrtQ - a / 3;
*x2 = 2 * sqrtQ - a / 3;
}
return 3;
}
else if (R2 < Q3)
{
double sgnR = (R >= 0 ? 1 : -1);
double ratio = sgnR * sqrt(R2 / Q3);
double theta = acos(ratio);
double norm = -2 * sqrt(Q);
*x0 = norm * cos(theta / 3) - a / 3;
*x1 = norm * cos((theta + 2.0 * M_PI) / 3) - a / 3;
*x2 = norm * cos((theta - 2.0 * M_PI) / 3) - a / 3;
/* Sort *x0, *x1, *x2 into increasing order */
if (*x0 > *x1) mtools::swap(*x0, *x1);
if (*x1 > *x2)
{
mtools::swap(*x1, *x2);
if (*x0 > *x1) mtools::swap(*x0, *x1);
}
return 3;
}
else
{
double sgnR = (R >= 0 ? 1 : -1);
double A = -sgnR * pow(fabs(R) + sqrt(R2 - Q3), 1.0 / 3.0);
double B = Q / A;
*x0 = A + B - a / 3;
return 1;
}
}
