#include "openmc/reaction.h"

#include <algorithm> // for remove_if

#include <string>

#include <unordered_map>

#include <utility> // for move

#include <fmt/core.h>

#include "openmc/chain.h"

#include "openmc/constants.h"

#include "openmc/endf.h"

#include "openmc/hdf5_interface.h"

#include "openmc/random_lcg.h"

#include "openmc/search.h"

#include "openmc/secondary_uncorrelated.h"

#include "openmc/settings.h"

namespace openmc {

//==============================================================================

// Reaction implementation

//==============================================================================

Reaction::Reaction(

hid_t group, const vector<int>& temperatures, std::string name)

{

read_attribute(group, "Q_value", q_value_);

read_attribute(group, "mt", mt_);

int tmp;

read_attribute(group, "center_of_mass", tmp);

scatter_in_cm_ = (tmp == 1);

// Checks if redudant attribute exists before loading

// (for compatibiltiy with legacy .h5 libraries)

if (attribute_exists(group, "redundant")) {

read_attribute(group, "redundant", tmp);

redundant_ = (tmp == 1);

} else {

redundant_ = false;

}

// Read cross section and threshold_idx data

for (auto t : temperatures) {

// Get group corresponding to temperature

hid_t temp_group = open_group(group, fmt::format("{}K", t).c_str());

hid_t dset = open_dataset(temp_group, "xs");

// Get threshold index

TemperatureXS xs;

read_attribute(dset, "threshold_idx", xs.threshold);

// Read cross section values

read_dataset(dset, xs.value);

close_dataset(dset);

close_group(temp_group);

// create new entry in xs vector

xs_.push_back(std::move(xs));

}

// Read products

for (const auto& name : group_names(group)) {

if (name.rfind("product_", 0) == 0) {

hid_t pgroup = open_group(group, name.c_str());

products_.emplace_back(pgroup);

close_group(pgroup);

}

}

if (settings::use_decay_photons) {

// Remove photon products for D1S method

products_.erase(std::remove_if(products_.begin(), products_.end(),

[](const auto& p) { return p.particle_.is_photon(); }),

products_.end());

// Determine product for D1S method

auto nuclide_it = data::chain_nuclide_map.find(name);

if (nuclide_it != data::chain_nuclide_map.end()) {

const auto& chain_nuc = data::chain_nuclides[nuclide_it->second];

const auto& rx_products = chain_nuc->reaction_products();

auto product_it = rx_products.find(mt_);

if (product_it != rx_products.end()) {

auto decay_products = product_it->second;

for (const auto& decay_product : decay_products) {

auto product_it = data::chain_nuclide_map.find(decay_product.name);

if (product_it != data::chain_nuclide_map.end()) {

const auto& product_nuc = data::chain_nuclides[product_it->second];

if (product_nuc->photon_energy()) {

products_.emplace_back(decay_product);

}

}

}

}

}

}

}

double Reaction::xs(int64_t i_temp, int64_t i_grid, double interp_factor) const

{

// If energy is below threshold, return 0. Otherwise interpolate between

// nearest grid points

const auto& x = xs_[i_temp];

return (i_grid < x.threshold)

? 0.0

: (1.0 - interp_factor) * x.value[i_grid - x.threshold] +

interp_factor * x.value[i_grid - x.threshold + 1];

}

double Reaction::xs(const NuclideMicroXS& micro) const

{

return this->xs(micro.index_temp, micro.index_grid, micro.interp_factor);

}

double Reaction::collapse_rate(int64_t i_temp, span<const double> energy,

span<const double> flux, const vector<double>& grid) const

{

// Find index corresponding to first energy

const auto& xs = xs_[i_temp].value;

int i_low = lower_bound_index(grid.cbegin(), grid.cend(), energy.front());

// Check for threshold and adjust starting point if necessary

int j_start = 0;

int i_threshold = xs_[i_temp].threshold;

if (i_low < i_threshold) {

i_low = i_threshold;

while (energy[j_start + 1] < grid[i_low]) {

++j_start;

if (j_start + 1 == energy.size())

return 0.0;

}

}

double xs_flux_sum = 0.0;

for (int j = j_start; j < flux.size(); ++j) {

double E_group_low = energy[j];

double E_group_high = energy[j + 1];

double flux_per_eV = flux[j] / (E_group_high - E_group_low);

// Determine energy grid index corresponding to group high

int i_high = i_low;

while (grid[i_high + 1] < E_group_high && i_high + 1 < grid.size() - 1)

++i_high;

// Loop over energy grid points within [E_group_low, E_group_high]

for (; i_low <= i_high; ++i_low) {

// Determine bounding grid energies and cross sections

double E_l = grid[i_low];

double E_r = grid[i_low + 1];

if (E_l == E_r)

continue;

double xs_l = xs[i_low - i_threshold];

double xs_r = xs[i_low + 1 - i_threshold];

// Determine actual energies

double E_low = std::max(E_group_low, E_l);

double E_high = std::min(E_group_high, E_r);

// Determine average cross section across segment

double m = (xs_r - xs_l) / (E_r - E_l);

double xs_low = xs_l + m * (E_low - E_l);

double xs_high = xs_l + m * (E_high - E_l);

double xs_avg = 0.5 * (xs_low + xs_high);

// Add contribution from segment

double dE = (E_high - E_low);

xs_flux_sum += flux_per_eV * xs_avg * dE;

}

i_low = i_high;

// Check for end of energy grid

if (i_low + 1 == grid.size())

break;

}

return xs_flux_sum;

}

//==============================================================================

// Non-member functions

//==============================================================================

std::unordered_map<int, std::string> REACTION_NAME_MAP {

{SCORE_FLUX, "flux"},

{SCORE_TOTAL, "total"},

{SCORE_SCATTER, "scatter"},

{SCORE_NU_SCATTER, "nu-scatter"},

{SCORE_ABSORPTION, "absorption"},

{SCORE_FISSION, "fission"},

{SCORE_NU_FISSION, "nu-fission"},

{SCORE_DECAY_RATE, "decay-rate"},

{SCORE_DELAYED_NU_FISSION, "delayed-nu-fission"},

{SCORE_PROMPT_NU_FISSION, "prompt-nu-fission"},

{SCORE_KAPPA_FISSION, "kappa-fission"},

{SCORE_CURRENT, "current"},

{SCORE_EVENTS, "events"},

{SCORE_INVERSE_VELOCITY, "inverse-velocity"},

{SCORE_FISS_Q_PROMPT, "fission-q-prompt"},

{SCORE_FISS_Q_RECOV, "fission-q-recoverable"},

{SCORE_PULSE_HEIGHT, "pulse-height"},

{SCORE_IFP_TIME_NUM, "ifp-time-numerator"},

{SCORE_IFP_BETA_NUM, "ifp-beta-numerator"},

{SCORE_IFP_DENOM, "ifp-denominator"},

// Normal ENDF-based reactions

{TOTAL_XS, "(n,total)"},

{ELASTIC, "(n,elastic)"},

{N_NONELASTIC, "(n,nonelastic)"},

{N_LEVEL, "(n,level)"},

{N_2ND, "(n,2nd)"},

{N_2N, "(n,2n)"},

{N_3N, "(n,3n)"},

{N_FISSION, "(n,fission)"},

{N_F, "(n,f)"},

{N_NF, "(n,nf)"},

{N_2NF, "(n,2nf)"},

{N_NA, "(n,na)"},

{N_N3A, "(n,n3a)"},

{N_2NA, "(n,2na)"},

{N_3NA, "(n,3na)"},

{N_NP, "(n,np)"},

{N_N2A, "(n,n2a)"},

{N_2N2A, "(n,2n2a)"},

{N_ND, "(n,nd)"},

{N_NT, "(n,nt)"},

{N_N3HE, "(n,n3He)"},

{N_ND2A, "(n,nd2a)"},

{N_NT2A, "(n,nt2a)"},

{N_4N, "(n,4n)"},

{N_3NF, "(n,3nf)"},

{N_2NP, "(n,2np)"},

{N_3NP, "(n,3np)"},

{N_N2P, "(n,n2p)"},

{N_NPA, "(n,npa)"},

{N_NC, "(n,nc)"},

{N_DISAPPEAR, "(n,disappear)"},

{N_GAMMA, "(n,gamma)"},

{N_P, "(n,p)"},

{N_D, "(n,d)"},

{N_T, "(n,t)"},

{N_3HE, "(n,3He)"},

{N_A, "(n,a)"},

{N_2A, "(n,2a)"},

{N_3A, "(n,3a)"},

{N_2P, "(n,2p)"},

{N_PA, "(n,pa)"},

{N_T2A, "(n,t2a)"},

{N_D2A, "(n,d2a)"},

{N_PD, "(n,pd)"},

{N_PT, "(n,pt)"},

{N_DA, "(n,da)"},

{N_5N, "(n,5n)"},

{N_6N, "(n,6n)"},

{N_2NT, "(n,2nt)"},

{N_TA, "(n,ta)"},

{N_4NP, "(n,4np)"},

{N_3ND, "(n,3nd)"},

{N_NDA, "(n,nda)"},

{N_2NPA, "(n,2npa)"},

{N_7N, "(n,7n)"},

{N_8N, "(n,8n)"},

{N_5NP, "(n,5np)"},

{N_6NP, "(n,6np)"},

{N_7NP, "(n,7np)"},

{N_4NA, "(n,4na)"},

{N_5NA, "(n,5na)"},

{N_6NA, "(n,6na)"},

{N_7NA, "(n,7na)"},

{N_4ND, "(n,4nd)"},

{N_5ND, "(n,5nd)"},

{N_6ND, "(n,6nd)"},

{N_3NT, "(n,3nt)"},

{N_4NT, "(n,4nt)"},

{N_5NT, "(n,5nt)"},

{N_6NT, "(n,6nt)"},

{N_2N3HE, "(n,2n3He)"},

{N_3N3HE, "(n,3n3He)"},

{N_4N3HE, "(n,4n3He)"},

{N_3N2P, "(n,3n2p)"},

{N_3N2A, "(n,3n2a)"},

{N_3NPA, "(n,3npa)"},

{N_DT, "(n,dt)"},

{N_NPD, "(n,npd)"},

{N_NPT, "(n,npt)"},

{N_NDT, "(n,ndt)"},

{N_NP3HE, "(n,np3He)"},

{N_ND3HE, "(n,nd3He)"},

{N_NT3HE, "(n,nt3He)"},

{N_NTA, "(n,nta)"},

{N_2N2P, "(n,2n2p)"},

{N_P3HE, "(n,p3He)"},

{N_D3HE, "(n,d3He)"},

{N_3HEA, "(n,3Hea)"},

{N_4N2P, "(n,4n2p)"},

{N_4N2A, "(n,4n2a)"},

{N_4NPA, "(n,4npa)"},

{N_3P, "(n,3p)"},

{N_N3P, "(n,n3p)"},

{N_3N2PA, "(n,3n2pa)"},

{N_5N2P, "(n,5n2p)"},

{201, "(n,Xn)"},

{202, "(n,Xgamma)"},

{N_XP, "(n,Xp)"},

{N_XD, "(n,Xd)"},

{N_XT, "(n,Xt)"},

{N_X3HE, "(n,X3He)"},

{N_XA, "(n,Xa)"},

{HEATING, "heating"},

{DAMAGE_ENERGY, "damage-energy"},

{PHOTON_TOTAL, "photon-total"},

{COHERENT, "coherent-scatter"},

{INCOHERENT, "incoherent-scatter"},

{PAIR_PROD_ELEC, "pair-production-electron"},

{PAIR_PROD, "pair-production"},

{PAIR_PROD_NUC, "pair-production-nuclear"},

{PHOTOELECTRIC, "photoelectric"},

{N_PC, "(n,pc)"},

{N_DC, "(n,dc)"},

{N_TC, "(n,tc)"},

{N_3HEC, "(n,3Hec)"},

{N_AC, "(n,ac)"},

{N_2NC, "(n,2nc)"},

{HEATING_LOCAL, "heating-local"},

};

std::unordered_map<std::string, int> REACTION_TYPE_MAP;

void initialize_maps()

{

// Add level reactions to name map

for (int level = 0; level <= 48; ++level) {

if (level >= 1 && level <= 40) {

REACTION_NAME_MAP[50 + level] = fmt::format("(n,n{})", level);

}

REACTION_NAME_MAP[600 + level] = fmt::format("(n,p{})", level);

REACTION_NAME_MAP[650 + level] = fmt::format("(n,d{})", level);

REACTION_NAME_MAP[700 + level] = fmt::format("(n,t{})", level);

REACTION_NAME_MAP[750 + level] = fmt::format("(n,3He{})", level);

REACTION_NAME_MAP[800 + level] = fmt::format("(n,a{})", level);

if (level <= 15) {

REACTION_NAME_MAP[875 + level] = fmt::format("(n,2n{})", level);

}

}

// Create photoelectric subshells

for (int mt = 534; mt <= 572; ++mt) {

REACTION_NAME_MAP[mt] =

fmt::format("photoelectric-{}", SUBSHELLS[mt - 534]);

}

// Invert name map to create type map

for (const auto& kv : REACTION_NAME_MAP) {

REACTION_TYPE_MAP[kv.second] = kv.first;

}

// Alternate names

REACTION_TYPE_MAP["elastic"] = ELASTIC;

REACTION_TYPE_MAP["n2n"] = N_2N;

REACTION_TYPE_MAP["n3n"] = N_3N;

REACTION_TYPE_MAP["n4n"] = N_4N;

REACTION_TYPE_MAP["H1-production"] = N_XP;

REACTION_TYPE_MAP["H2-production"] = N_XD;

REACTION_TYPE_MAP["H3-production"] = N_XT;

REACTION_TYPE_MAP["He3-production"] = N_X3HE;

REACTION_TYPE_MAP["He4-production"] = N_XA;

}

std::string reaction_name(int mt)

{

// Initialize remainder of name map and all of type map

if (REACTION_TYPE_MAP.empty())

initialize_maps();

// Get reaction name from map

auto it = REACTION_NAME_MAP.find(mt);

if (it != REACTION_NAME_MAP.end()) {

return it->second;

} else {

return fmt::format("MT={}", mt);

}

}

int reaction_tally_mt(std::string name)

{

// All "total" scores should map to the special SCORE_TOTAL

if (name == "total" || name == "(n,total)" || name == "photon-total")

return SCORE_TOTAL;

// All fission scores should map to the special SCORE_FISSION

if (name == "fission" || name == "(n,fission)")

return SCORE_FISSION;

// Delegate everything else to reaction_mt()

return reaction_mt(name);

}

int reaction_mt(const std::string& name)

{

// Initialize maps if needed

if (REACTION_TYPE_MAP.empty())

initialize_maps();

// Look up directly in type map (no score indirection)

auto it = REACTION_TYPE_MAP.find(name);

if (it != REACTION_TYPE_MAP.end()) {

int mt = it->second;

return mt;

}

// Assume the given string is an MT number

int MT = 0;

try {

MT = std::stoi(name);

} catch (const std::invalid_argument& ex) {

throw std::invalid_argument("Unknown reaction name \"" + name + "\".");

}

if (MT < 1)

throw std::invalid_argument("Unknown reaction name \"" + name + "\".");

return MT;

}

} // namespace openmc