diff options
| -rw-r--r-- | libdimension/polynomial.c | 48 |
1 files changed, 24 insertions, 24 deletions
diff --git a/libdimension/polynomial.c b/libdimension/polynomial.c index 136b0b5..68970ee 100644 --- a/libdimension/polynomial.c +++ b/libdimension/polynomial.c @@ -320,11 +320,10 @@ static inline size_t dmnsn_solve_linear(const double poly[2], double x[1]) { x[0] = -poly[0]; - if (x[0] >= dmnsn_epsilon) { + if (x[0] >= dmnsn_epsilon) return 1; - } else { + else return 0; - } } /** Solve a normalized quadratic polynomial algebraically. */ @@ -336,13 +335,13 @@ dmnsn_solve_quadratic(const double poly[3], double x[2]) double s = sqrt(disc); x[0] = (-poly[1] + s)/2.0; x[1] = (-poly[1] - s)/2.0; - if (x[1] >= dmnsn_epsilon) { + + if (x[1] >= dmnsn_epsilon) return 2; - } else if (x[0] >= dmnsn_epsilon) { + else if (x[0] >= dmnsn_epsilon) return 1; - } else { + else return 0; - } } else { return 0; } @@ -370,20 +369,12 @@ dmnsn_solve_cubic(double poly[4], double x[3]) x[0] = -2.0*msqrtp3*cos(4.0*atan(1.0)/3.0 - theta) - bdiv3; x[1] = -(x[0] + x[2] + poly[2]); - if (x[2] >= dmnsn_epsilon) { + if (x[2] >= dmnsn_epsilon) return 3; - } else if (x[1] >= dmnsn_epsilon) { + else if (x[1] >= dmnsn_epsilon) return 2; - } else if (x[0] >= dmnsn_epsilon) { - return 1; - } else { - return 0; - } - } else { + } else if (disc >= dmnsn_epsilon) { /* One real root */ - if (disc < 0.0) - disc = 0.0; - double cbrtdiscq = cbrt(sqrt(disc/108.0) + fabs(q)/2.0); double abst = cbrtdiscq - p/(3.0*cbrtdiscq); @@ -392,13 +383,22 @@ dmnsn_solve_cubic(double poly[4], double x[3]) } else { x[0] = abst - bdiv3; } - - if (x[0] >= dmnsn_epsilon) { - return 1; - } else { - return 0; - } + } else if (fabs(p) < dmnsn_epsilon) { + /* Equation is a perfect cube */ + x[0] = -bdiv3; + } else { + /* Two real roots; one duplicate */ + double t1 = 3.0*q/p, t2 = -t1/2.0; + x[0] = dmnsn_max(t1, t2); + x[1] = dmnsn_min(t1, t2); + if (x[1] >= dmnsn_epsilon) + return 2; } + + if (x[0] >= dmnsn_epsilon) + return 1; + else + return 0; } /* Uspensky's algorithm */ |