Constants.hpp

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// SPDX-License-Identifier: Apache-2.0
//
// Copyright 2026 Caleb Buahin
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

 
#ifndef OPENSWMM_CONSTANTS_HPP
#define OPENSWMM_CONSTANTS_HPP
 
namespace openswmm {
 
// ============================================================================
// Physical constants
// ============================================================================
 
namespace constants {

constexpr double GRAVITY = 32.2;

constexpr double SQRT_GRAVITY = 5.67450438786; // sqrt(32.2)

constexpr double INV_SQRT_GRAVITY = 0.17622692584; // 1.0 / sqrt(32.2)

constexpr double PI = 3.141592654;

constexpr double PHI = 1.486;

constexpr double MEXP = 5.0 / 3.0;

constexpr double VISCOS = 1.1e-5;

constexpr double SEC_PER_DAY = 86400.0;

constexpr double FT_PER_IN = 1.0 / 12.0;

constexpr double IN_PER_FT = 12.0;
 
// ============================================================================
// Numerical thresholds and tolerances
// ============================================================================

constexpr double FUDGE = 0.0001;

constexpr double MIN_SURFAREA = 12.566; // 4*pi

constexpr double FLOW_TOL = 0.00001;

constexpr double MIN_DELTA_Z = 0.001;

constexpr double XTOL = 0.001;

constexpr double TINY = 1.0e-6;

static constexpr double MISSING = -1.0e10;
 
// ============================================================================
// Dynamic wave solver constants
// ============================================================================

constexpr double OMEGA = 0.5;

constexpr double DEFAULT_HEAD_TOL = 0.005;

constexpr int DEFAULT_MAX_TRIALS = 8;

constexpr double MAX_VELOCITY = 50.0;

constexpr double MIN_TIMESTEP = 0.001;

constexpr double EXTRAN_CROWN_CUTOFF = 0.96;

constexpr double SLOT_CROWN_CUTOFF = 0.985257;

constexpr double SLOT_WIDTH_FACTOR = 0.001;
 
// ============================================================================
// ODE solver constants (RK45 Cash-Karp)
// ============================================================================
 
namespace ode {

constexpr int MAX_STEPS = 10000;

constexpr double ODE_TINY = 1.0e-30;

constexpr double SAFETY = 0.9;

constexpr double PGROW = -0.2;

constexpr double PSHRNK = -0.25;

constexpr double ERRCON = 1.89e-4;

constexpr double GWTOL = 0.0001;

constexpr double ODETOL = 0.0001;
 
} // namespace ode
 
// ============================================================================
// Hydraulic structure constants
// ============================================================================

constexpr double MIN_LINK_FLOW = 0.001;
 
// ============================================================================
// Cross-section constants
// ============================================================================

constexpr double RECT_ALFMAX = 0.97;

constexpr double TRAP_ALFMAX = 0.98;

constexpr int N_TRANSECT_TBL = 51;

constexpr int MAX_SHAPES = 26;
 
// ============================================================================
// Data structure constants
// ============================================================================

constexpr int N_FLOW_CLASSES = 7;

constexpr int MAX_PAST_RAIN = 48;

constexpr int N_TIME_BINS = 5;

constexpr int DATE_DELTA = 693594;
 
} // namespace constants
} // namespace openswmm
 
#endif // OPENSWMM_CONSTANTS_HPP