openswmm::ode Namespace Reference

Typedefs
using	DerivFunc = std::function< void(double x, const double *y, double *dydx)>
	Derivative function signature.
using	BatchDerivFunc = std::function< void(double x, const double *y0, const double *y1, double *dy0, double *dy1, int n_sys)>
	Integrate N independent 2-equation ODE systems in batch.

Functions
int	integrate (double *y, int n, double x1, double x2, double eps, double h1, const DerivFunc &derivs)
	Integrate an ODE system from x1 to x2 using RK45 Cash-Karp.
int	integrate_batch_2eq (double *y0, double *y1, int n_sys, double x1, double x2, double eps, double h1, const BatchDerivFunc &derivs)

Variables
constexpr int	MAXSTP = 10000
	Maximum integration steps.
constexpr double	TINY = 1.0e-30
	Underflow protection.
constexpr double	SAFETY = 0.9
	Step adjustment safety factor.
constexpr double	PGROW = -0.2
	Exponent for step increase.
constexpr double	PSHRNK = -0.25
	Exponent for step decrease.
constexpr double	ERRCON = 1.89e-4
	= (5/SAFETY)^(1/PGROW)
constexpr int	ODE_OK = 0
	Success.
constexpr int	ODE_TOO_MANY = 1
	n > allocated max
constexpr int	ODE_UNDERFLOW = 2
	Step size underflowed.
constexpr int	ODE_MAX_STEPS = 3
	Exceeded MAXSTP.

Typedef Documentation

BatchDerivFunc

using openswmm::ode::BatchDerivFunc = typedef std::function<void(double x, const double* y0, const double* y1, double* dy0, double* dy1, int n_sys)>

Integrate N independent 2-equation ODE systems in batch.

Used by groundwater: each subcatchment has 2 state variables (theta, lower_depth). All are integrated over the same interval [x1, x2] but with independent derivative functions.

The batch version avoids per-subcatchment function call overhead and enables future SIMD parallelism of the RK stages.

Parameters

y0	[in/out] SoA: first state variable for all N systems.
y1	[in/out] SoA: second state variable for all N systems.
n_sys	Number of independent ODE systems.
x1	Start of interval.
x2	End of interval.
eps	Tolerance.
h1	Initial step size.
derivs	Batch derivative: derivs(x, y0[], y1[], dy0[], dy1[], n_sys).

DerivFunc

using openswmm::ode::DerivFunc = typedef std::function<void(double x, const double* y, double* dydx)>

Derivative function signature.

Parameters

x	Independent variable (e.g., time).
y	Array of n dependent variables at x.
dydx	[out] Array where callback writes dy_i/dx.

Function Documentation

integrate()

int openswmm::ode::integrate	(	double *	y,
		int	n,
		double	x1,
		double	x2,
		double	eps,
		double	h1,
		const DerivFunc &	derivs
	)

Integrate an ODE system from x1 to x2 using RK45 Cash-Karp.

Parameters

y	[in/out] Array of n dependent variables (initial → final).
n	Number of equations.
x1	Start of integration interval.
x2	End of integration interval.
eps	Desired accuracy (tolerance).
h1	Initial step size guess.
derivs	Derivative callback function.

Returns

ODE_OK on success, or error code.

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integrate_batch_2eq()

int openswmm::ode::integrate_batch_2eq	(	double *	y0,
		double *	y1,
		int	n_sys,
		double	x1,
		double	x2,
		double	eps,
		double	h1,
		const BatchDerivFunc &	derivs
	)

Variable Documentation

ERRCON

constexpr double openswmm::ode::ERRCON = 1.89e-4

constexpr

= (5/SAFETY)^(1/PGROW)

MAXSTP

constexpr int openswmm::ode::MAXSTP = 10000

constexpr

Maximum integration steps.

ODE_MAX_STEPS

constexpr int openswmm::ode::ODE_MAX_STEPS = 3

constexpr

Exceeded MAXSTP.

ODE_OK

constexpr int openswmm::ode::ODE_OK = 0

constexpr

Success.

ODE_TOO_MANY

constexpr int openswmm::ode::ODE_TOO_MANY = 1

constexpr

n > allocated max

ODE_UNDERFLOW

constexpr int openswmm::ode::ODE_UNDERFLOW = 2

constexpr

Step size underflowed.

PGROW

constexpr double openswmm::ode::PGROW = -0.2

constexpr

Exponent for step increase.

PSHRNK

constexpr double openswmm::ode::PSHRNK = -0.25

constexpr

Exponent for step decrease.

SAFETY

constexpr double openswmm::ode::SAFETY = 0.9

constexpr

Step adjustment safety factor.

TINY

constexpr double openswmm::ode::TINY = 1.0e-30

constexpr

Underflow protection.