Andreas Suter
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122 lines
4.7 KiB
C++
122 lines
4.7 KiB
C++
/***************************************************************************
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PUserFcn.cpp
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Author: Andreas Suter
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e-mail: andreas.suter@psi.ch
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***************************************************************************/
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/***************************************************************************
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* Copyright (C) 2007-2025 by Andreas Suter *
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* andreas.suter@psi.ch *
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* *
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* This program is free software; you can redistribute it and/or modify *
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* it under the terms of the GNU General Public License as published by *
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* the Free Software Foundation; either version 2 of the License, or *
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* (at your option) any later version. *
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* *
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* This program is distributed in the hope that it will be useful, *
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* but WITHOUT ANY WARRANTY; without even the implied warranty of *
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the *
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* GNU General Public License for more details. *
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* *
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* You should have received a copy of the GNU General Public License *
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* along with this program; if not, write to the *
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* Free Software Foundation, Inc., *
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* 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. *
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***************************************************************************/
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#include <cassert>
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#include "PUserFcn.h"
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ClassImp(PUserFcn)
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//------------------------------------------------------
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/**
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* \brief Default constructor for PUserFcn.
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*
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* Initializes a third-order polynomial user function. This implementation
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* requires no special initialization as it has no internal state - all
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* computation is done directly in the operator() method.
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*
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* \note This simple constructor serves as a template for more complex user
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* functions. Functions requiring initialization (e.g., loading lookup tables,
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* precomputing constants) should perform that work here or in SetGlobalPart().
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*/
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PUserFcn::PUserFcn()
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{
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}
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//------------------------------------------------------
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/**
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* \brief Destructor for PUserFcn.
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*
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* Cleans up any resources allocated by the polynomial function. Since this
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* implementation has no dynamically allocated resources, the destructor is
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* empty.
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*
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* \note User functions with allocated resources (lookup tables, buffers,
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* external library handles) must clean them up here to prevent memory leaks.
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* If using the global part interface, ensure proper coordination with
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* gGlobalUserFcn cleanup.
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*/
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PUserFcn::~PUserFcn()
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{
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}
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//------------------------------------------------------
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/**
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* \brief Evaluates the third-order polynomial at the given time.
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*
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* Computes a cubic polynomial of the form:
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*
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* \f[ P(t) = c_0 + c_1 t + c_2 t^2 + c_3 t^3 = \sum_{k=0}^{3} c_k t^k \f]
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*
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* where the coefficients \f$c_k\f$ are provided in the parameter vector.
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*
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* \section puserfcn_op_example Example MSR Configuration
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*
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* \code
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* FITPARAMETER
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* # No Name Value Step Pos_Error Boundaries
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* 1 c0 0.95 0.01 none
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* 2 c1 -0.001 0.0001 none
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* 3 c2 0.00001 0.000001 none
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* 4 c3 0.0 0.0000001 none 0 none (fixed to zero for quadratic)
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*
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* THEORY
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* userFcn libPUserFcn.so PUserFcn 1 2 3 4
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* \endcode
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*
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* \section puserfcn_op_notes Implementation Notes
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*
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* - Uses direct polynomial evaluation (Horner's method could improve
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* numerical stability for high-precision applications)
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* - Asserts exactly 4 parameters to catch MSR file configuration errors
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* - No special handling for negative time values
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*
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* \param t Independent variable (time in μs for μSR, or general x-axis
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* value for non-μSR fits)
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* \param param Vector containing exactly 4 polynomial coefficients:
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* - param[0]: \f$c_0\f$ - constant term (dimensionless)
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* - param[1]: \f$c_1\f$ - linear coefficient (μs⁻¹)
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* - param[2]: \f$c_2\f$ - quadratic coefficient (μs⁻²)
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* - param[3]: \f$c_3\f$ - cubic coefficient (μs⁻³)
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*
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* \return The polynomial value \f$P(t)\f$ at the specified time
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*
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* \pre param.size() == 4 (enforced by assertion)
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*
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* \see PUserFcnBase::operator() for the virtual interface specification
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*/
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Double_t PUserFcn::operator()(Double_t t, const std::vector<Double_t> ¶m) const
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{
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// expected parameters: c0, c1, c2, c3
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assert(param.size() == 4);
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return param[0] + param[1]*t + param[2]*t*t + param[3]*t*t*t;
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}
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