ConstantStepOdeSolver.cc

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#include <cassert>

#include "CalibCalorimetry/HcalAlgos/interface/ConstantStepOdeSolver.h"

inline static double interpolateLinear(const double x, const double f0,
                                       const double f1)
{
    return f0*(1.0 - x) + f1*x;
}

double ConstantStepOdeSolver::getPeakTime(const unsigned which) const
{
    if (which >= dim_) throw cms::Exception(
        "In ConstantStepOdeSolver::getPeakTime: index out of range");
    if (runLen_ < 3) throw cms::Exception(
        "In ConstantStepOdeSolver::getPeakTime: not enough data");

    const double* hbuf = &historyBuffer_[which];
    double maxval = hbuf[0];
    unsigned maxind = 0;
    for (unsigned i=1; i<runLen_; ++i)
        if (hbuf[dim_*i] > maxval)
        {
            maxval = hbuf[dim_*i];
            maxind = i;
        }
    if (maxind == 0U)
        return 0.0;
    if (maxind == runLen_-1U)
        return dt_*maxind;
    const double l = hbuf[dim_*(maxind - 1U)];
    const double r = hbuf[dim_*(maxind + 1U)];
    if (l < maxval || r < maxval)
        return dt_*(maxind + (l - r)/2.0/(l + r - 2.0*maxval));
    else
        return dt_*maxind;
}

double ConstantStepOdeSolver::getIntegrated(
    const unsigned which, const unsigned idx) const
{
    if (which >= dim_ || idx >= runLen_) throw cms::Exception(
        "In ConstantStepOdeSolver::getIntegrated: index out of range");
    if (lastIntegrated_ != which)
        (const_cast<ConstantStepOdeSolver*>(this))->integrateCoordinate(which);
    return chargeBuffer_[idx];
}

void ConstantStepOdeSolver::integrateCoordinate(const unsigned which)
{
    if (runLen_ < 4) throw cms::Exception(
        "In ConstantStepOdeSolver::integrateCoordinate: not enough data");
    if (chargeBuffer_.size() < runLen_)
        chargeBuffer_.resize(runLen_);
    double* integ = &chargeBuffer_[0];
    const double* coord = &historyBuffer_[which];

    integ[0] = 0.0;
    integ[1] = coord[dim_*0]*(3.0/8.0) +
               coord[dim_*1]*(19.0/24.0) +
               coord[dim_*2]*(-5.0/24.0) +
               coord[dim_*3]*(1.0/24.0);
    long double sum = integ[1];
    const unsigned rlenm1 = runLen_ - 1U;
    for (unsigned i=2; i<rlenm1; ++i)
    {
        sum += (coord[dim_*(i-2U)]*(-1.0/24.0) +
                coord[dim_*(i-1U)]*(13.0/24.0) +
                coord[dim_*i]     *(13.0/24.0) +
                coord[dim_*(i+1U)]*(-1.0/24.0));
        integ[i] = sum;
    }
    sum += (coord[dim_*rlenm1]     *(3.0/8.0) +
            coord[dim_*(rlenm1-1U)]*(19.0/24.0) +
            coord[dim_*(rlenm1-2U)]*(-5.0/24.0) +
            coord[dim_*(rlenm1-3U)]*(1.0/24.0));
    integ[rlenm1] = sum;                                      
    if (dt_ != 1.0)
        for (unsigned i=1; i<runLen_; ++i)
            integ[i] *= dt_;
    lastIntegrated_ = which;
}

void ConstantStepOdeSolver::writeHistory(std::ostream& os,
                                         const double dt,
                                         const bool cubic) const
{
    os << "# " << this->methodName() << '\n';
    if (dim_ && runLen_)
    {
        if (dt == dt_)
        {
            for (unsigned ipt=0; ipt<runLen_; ++ipt)
            {
                os << getTime(ipt);
                for (unsigned which=0; which<dim_; ++which)
                    os << ' ' << getCoordinate(which, ipt);
                os << '\n';
            }
        }
        else
        {
            const double tmax = lastMaxT();
            for (unsigned i=0; ; ++i)
            {
                const double t = i*dt;
                if (t > tmax)
                    break;
                os << t;
                for (unsigned which=0; which<dim_; ++which)
                    os << ' ' << interpolateCoordinate(which, t, cubic);
                os << '\n';
            }
        }
    }
}

void ConstantStepOdeSolver::writeIntegrated(std::ostream& os,
                                            const unsigned which,
                                            const double dt,
                                            const bool cubic) const
{
    os << "# " << this->methodName() << '\n';
    if (dim_ && runLen_)
    {
        if (dt == dt_)
        {
            for (unsigned ipt=0; ipt<runLen_; ++ipt)
                os << getTime(ipt) << ' ' << getIntegrated(which, ipt) << '\n';
        }
        else
        {
            const double tmax = lastMaxT();
            for (unsigned i=0; ; ++i)
            {
                const double t = i*dt;
                if (t > tmax)
                    break;
                os << t << ' ' << interpolateIntegrated(which, t, cubic) << '\n';
            }
        }
    }
}

ConstantStepOdeSolver::ConstantStepOdeSolver(const ConstantStepOdeSolver& r)
    : rhs_(nullptr),
      dt_(r.dt_),
      dim_(r.dim_),
      runLen_(r.runLen_),
      lastIntegrated_(r.lastIntegrated_),
      historyBuffer_(r.historyBuffer_),
      chargeBuffer_(r.chargeBuffer_)
{
    if (r.rhs_)
        rhs_ = r.rhs_->clone();
}

ConstantStepOdeSolver& ConstantStepOdeSolver::operator=(
    const ConstantStepOdeSolver& r)
{
    if (this != &r)
    {
        delete rhs_; rhs_ = nullptr;
        dt_ = r.dt_;
        dim_ = r.dim_;
        runLen_ = r.runLen_;
        lastIntegrated_ = r.lastIntegrated_;
        historyBuffer_ = r.historyBuffer_;
        chargeBuffer_ = r.chargeBuffer_;
        if (r.rhs_)
            rhs_ = r.rhs_->clone();
    }
    return *this;
}

void ConstantStepOdeSolver::truncateCoordinate(const unsigned which,
                                               const double minValue,
                                               const double maxValue)
{
    if (which >= dim_) throw cms::Exception(
        "In ConstantStepOdeSolver::truncateCoordinate: index out of range");
    if (minValue > maxValue) throw cms::Exception(
        "In ConstantStepOdeSolver::truncateCoordinate: invalid truncation range");

    double* buf = &historyBuffer_[which];
    for (unsigned i=0; i<runLen_; ++i)
    {
        if (buf[dim_*i] < minValue)
            buf[dim_*i] = minValue;
        else if (buf[dim_*i] > maxValue)
            buf[dim_*i] = maxValue;
    }
}

double ConstantStepOdeSolver::interpolateCoordinate(
    const unsigned which, const double t, const bool cubic) const
{
    if (which >= dim_) throw cms::Exception(
        "In ConstantStepOdeSolver::interpolateCoordinate: index out of range");
    if (runLen_ < 2U || (cubic && runLen_ < 4U)) throw cms::Exception(
        "In ConstantStepOdeSolver::interpolateCoordinate: not enough data");
    const double maxt = runLen_ ? dt_*(runLen_-1U) : 0.0;
    if (t < 0.0 || t > maxt) throw cms::Exception(
        "In ConstantStepOdeSolver::interpolateCoordinate: time out of range");

    const double* arr = &historyBuffer_[0];
    if (t == 0.0)
        return arr[which];
    else if (t == maxt)
        return arr[which + dim_*(runLen_-1U)];

    // Translate time into timestep units
    const double tSteps = t/dt_;
    unsigned nLow = tSteps;
    if (nLow >= runLen_ - 1)
        nLow = runLen_ - 2;
    double x = tSteps - nLow;

    if (cubic)
    {
        unsigned i0 = 0;
        if (nLow == runLen_ - 2)
        {
            i0 = nLow - 2U;
            x += 2.0;
        }
        else if (nLow)
        {
            i0 = nLow - 1U;
            x += 1.0;
        }
        const double* base = arr + (which + dim_*i0);
        return interpolateLinear(x*(3.0 - x)/2.0,
                                 interpolateLinear(x/3.0, base[0], base[dim_*3]),
                                 interpolateLinear(x-1.0, base[dim_], base[dim_*2]));
    }
    else
        return interpolateLinear(x, arr[which+dim_*nLow], arr[which+dim_*(nLow+1U)]);
}

double ConstantStepOdeSolver::interpolateIntegrated(
    const unsigned which, const double t, const bool cubic) const
{
    if (which >= dim_) throw cms::Exception(
        "In ConstantStepOdeSolver::interpolateIntegrated: index out of range");
    if (runLen_ < 2U || (cubic && runLen_ < 4U)) throw cms::Exception(
        "In ConstantStepOdeSolver::interpolateIntegrated: not enough data");
    const double maxt = runLen_ ? dt_*(runLen_-1U) : 0.0;
    if (t < 0.0 || t > maxt) throw cms::Exception(
        "In ConstantStepOdeSolver::interpolateIntegrated: time out of range");
    if (lastIntegrated_ != which)
        (const_cast<ConstantStepOdeSolver*>(this))->integrateCoordinate(which);

    const double* buf = &chargeBuffer_[0];
    if (t == 0.0)
        return buf[0];
    else if (t == maxt)
        return buf[runLen_-1U];

    // Translate time into timestep units
    const double tSteps = t/dt_;
    unsigned nLow = tSteps;
    if (nLow >= runLen_ - 1)
        nLow = runLen_ - 2;
    double x = tSteps - nLow;

    if (cubic)
    {
        unsigned i0 = 0;
        if (nLow == runLen_ - 2)
        {
            i0 = nLow - 2U;
            x += 2.0;
        }
        else if (nLow)
        {
            i0 = nLow - 1U;
            x += 1.0;
        }
        const double* base = buf + i0;
        return interpolateLinear(x*(3.0 - x)/2.0,
                                 interpolateLinear(x/3.0, base[0], base[3]),
                                 interpolateLinear(x-1.0, base[1], base[2]));
    }
    else
        return interpolateLinear(x, buf[nLow], buf[nLow+1U]);
}

void ConstantStepOdeSolver::setHistory(const double dt, const double* data,
                                       const unsigned dim, const unsigned runLen)
{
    const unsigned len = dim*runLen;
    if (!len)
        return;
    if (dt <= 0.0) throw cms::Exception(
        "In ConstantStepOdeSolver::setHistory: can not run backwards in time");
    assert(data);
    const unsigned sz = dim*(runLen + 1U);
    if (historyBuffer_.size() < sz)
        historyBuffer_.resize(sz);
    dt_ = dt;
    dim_ = dim;
    runLen_ = runLen;
    lastIntegrated_ = dim_;
    double* arr = &historyBuffer_[0];
    for (unsigned i=0; i<len; ++i)
        *arr++ = *data++;
    for (unsigned i=0; i<dim; ++i)
        *arr++ = 0.0;
}

void ConstantStepOdeSolver::run(const double* initialConditions,
                                const unsigned lenInitialConditions,
                                const double dt, const unsigned nSteps)
{
    if (!nSteps || !lenInitialConditions)
        return;
    if (!rhs_) throw cms::Exception(
        "In ConstantStepOdeSolver::run: ODE right hand side has not been set");
    if (dt <= 0.0) throw cms::Exception(
        "In ConstantStepOdeSolver::run: can not run backwards in time");
    assert(initialConditions);
    dt_ = dt;
    dim_ = lenInitialConditions;
    lastIntegrated_ = dim_;
    runLen_ = nSteps + 1U;
    const unsigned sz = (runLen_+1U)*dim_;
    if (historyBuffer_.size() < sz)
        historyBuffer_.resize(sz);
    double* arr = &historyBuffer_[0];
    for (unsigned i=0; i<lenInitialConditions; ++i)
        arr[i] = initialConditions[i];
    double* stepBuffer = arr + runLen_*dim_;

    for (unsigned i = 0; i < nSteps; ++i, arr += lenInitialConditions)
    {
        const double t = i*dt;
        this->step(t, dt, arr, lenInitialConditions, stepBuffer);
        double* next = arr + lenInitialConditions;
        for (unsigned i=0; i<lenInitialConditions; ++i)
            next[i] = arr[i] + stepBuffer[i];
    }
}

void EulerOdeSolver::step(const double t, const double dt,
                          const double* x, const unsigned lenX,
                          double* coordIncrement) const
{
    rhs_->calc(t, x, lenX, coordIncrement);
    for (unsigned i=0; i<lenX; ++i)
        coordIncrement[i] *= dt;
}

void RK2::step(const double t, const double dt,
               const double* x, const unsigned lenX,
               double* coordIncrement) const
{
    const double halfstep = dt/2.0;
    if (buf_.size() < lenX)
        buf_.resize(lenX);
    double* midpoint = &buf_[0];
    rhs_->calc(t, x, lenX, midpoint);
    for (unsigned i=0; i<lenX; ++i)
    {
        midpoint[i] *= halfstep;
        midpoint[i] += x[i];
    }
    rhs_->calc(t + halfstep, midpoint, lenX, coordIncrement);
    for (unsigned i=0; i<lenX; ++i)
        coordIncrement[i] *= dt;
}

void RK4::step(const double t, const double dt,
               const double* x, const unsigned lenX,
               double* coordIncrement) const
{
    const double halfstep = dt/2.0;
    if (buf_.size() < 4*lenX)
        buf_.resize(4*lenX);
    double* k1x = &buf_[0];
    double* k2x = k1x + lenX;
    double* k3x = k2x + lenX;
    double* k4x = k3x + lenX;
    rhs_->calc(t, x, lenX, k1x);
    for (unsigned i=0; i<lenX; ++i)
        coordIncrement[i] = x[i] + halfstep*k1x[i];
    rhs_->calc(t + halfstep, coordIncrement, lenX, k2x);
    for (unsigned i=0; i<lenX; ++i)
        coordIncrement[i] = x[i] + halfstep*k2x[i];
    rhs_->calc(t + halfstep, coordIncrement, lenX, k3x);
    for (unsigned i=0; i<lenX; ++i)
        coordIncrement[i] = x[i] + dt*k3x[i];
    rhs_->calc(t + dt, coordIncrement, lenX, k4x);
    for (unsigned i=0; i<lenX; ++i)
        coordIncrement[i] = dt/6.0*(k1x[i] + 2.0*(k2x[i] + k3x[i]) + k4x[i]);
}