From da1960ce5b968fdabb28ded86db4e96d32983c33 Mon Sep 17 00:00:00 2001
From: Ian Bell <ian.bell@nist.gov>
Date: Wed, 20 Oct 2021 16:29:04 -0400
Subject: [PATCH] Test tracing critical loci for nitrogen + ethane
---
include/teqp/algorithms/critical_tracing.hpp | 116 ++++++++++++++-----
src/tests/catch_test_multifluid.cxx | 27 +++++
2 files changed, 114 insertions(+), 29 deletions(-)
create mode 100644 src/tests/catch_test_multifluid.cxx
diff --git a/include/teqp/algorithms/critical_tracing.hpp b/include/teqp/algorithms/critical_tracing.hpp
index a7dc6f4..d38676b 100644
--- a/include/teqp/algorithms/critical_tracing.hpp
+++ b/include/teqp/algorithms/critical_tracing.hpp
@@ -6,6 +6,10 @@
#include <Eigen/Dense>
#include "teqp/algorithms/rootfinding.hpp"
+// Imports from boost
+#include <boost/numeric/odeint/stepper/controlled_runge_kutta.hpp>
+#include <boost/numeric/odeint/stepper/runge_kutta_cash_karp54.hpp>
+
template<typename Model, typename Scalar = double, typename VecType = Eigen::ArrayXd>
struct CriticalTracing {
/***
@@ -314,10 +318,7 @@ struct CriticalTracing {
static auto trace_critical_arclength_binary(const Model& model, const Scalar &T0, const VecType& rhovec0, const std::string& filename) -> nlohmann::json {
- double t = 0.0, dt = 100;
VecType last_drhodt;
- VecType rhovec = rhovec0;
- double T = T0;
auto dot = [](const auto& v1, const auto& v2) { return (v1 * v2).sum(); };
auto norm = [](const auto& v) { return sqrt((v * v).sum()); };
@@ -325,22 +326,71 @@ struct CriticalTracing {
auto JSONdata = nlohmann::json::array();
std::ofstream ofs = (filename.empty()) ? std::ofstream() : std::ofstream(filename);
- double c = 1.0;
- ofs << "z0 / mole frac.,rho0 / mol/m^3,rho1 / mol/m^3,T / K,p / Pa,c,dT/dt,drho0/dT,drho1/dT,condition(1),condition(2)" << std::endl;
- for (auto iter = 0; iter < 1000; ++iter) {
- auto rhotot = rhovec.sum();
- auto z0 = rhovec[0] / rhotot;
-
+ using state_type = std::vector<double>;
+ double c = 1.0;
+
+ // The function for the derivative in the form of odeint
+ // x is [T, rhovec]
+ auto xprime = [&model, &c, norm](const state_type& x, state_type& dxdt, const double /* t */)
+ {
+ const double& T = x[0];
+ const auto rhovec = Eigen::Map<const Eigen::ArrayXd>(&(x[0]) + 1, x.size() - 1);
+ auto drhodt = Eigen::Map<Eigen::ArrayXd>(&(dxdt[0]) + 1, dxdt.size() - 1);
auto drhodT = get_drhovec_dT_crit(model, T, rhovec).array().eval();
auto dTdt = 1.0 / norm(drhodT);
- auto drhodt = (drhodT * dTdt).eval();
+ dxdt[0] = c*dTdt;
+ drhodt = c*(drhodT * dTdt).eval();
+ };
- auto conditions = get_criticality_conditions(model, T, rhovec);
+ // Typedefs for the types
+ using namespace boost::numeric::odeint;
+ typedef runge_kutta_cash_karp54< state_type > error_stepper_type;
+ typedef controlled_runge_kutta< error_stepper_type > controlled_stepper_type;
+
+ // Define the tolerances
+ double abs_err = 1.0e-10, rel_err = 1.0e-6, a_x = 1.0, a_dxdt = 1.0;
+ controlled_stepper_type controlled_stepper(default_error_checker< double, range_algebra, default_operations >(abs_err, rel_err, a_x, a_dxdt));
+
+ double t = 0, dt = 0.1;
+
+ // Build the initial state arrary, T, followed by rhovec
+ std::vector<double> x0(rhovec0.size() + 1);
+
+ x0[0] = T0;
+ Eigen::Map<Eigen::ArrayXd>(&(x0[0]) + 1, x0.size() - 1) = rhovec0;
+
+ ofs << "z0 / mole frac.,rho0 / mol/m^3,rho1 / mol/m^3,T / K,p / Pa,c,dT/dt,drho0/dT,drho1/dT,condition(1),condition(2)" << std::endl;
+ for (auto iter = 0; iter < 1000; ++iter) {
+
+ // Make T and rhovec references to the contents of x0 vector
+ // The views are mutable (danger!)
+ double& T = x0[0];
+ auto rhovec = Eigen::Map<Eigen::ArrayXd>(&(x0[0]) + 1, x0.size() - 1);
+
+ {
+ auto dxdt = x0;
+ xprime(x0, dxdt, -1.0);
+ auto drhodt = Eigen::Map<Eigen::ArrayXd>(&(dxdt[0]) + 1, dxdt.size() - 1);
+
+ // Flip the sign if the tracing wants to go backwards, or if the first step would yield any negative concentrations
+ auto this_drhodt = (c * drhodt).eval();
+ auto step = rhovec + this_drhodt * dt;
+ Eigen::ArrayX<bool> negativestepvals = (step < 0).eval();
+ if (iter == 0 && negativestepvals.any()) {
+ c *= -1;
+ }
+ else if (iter > 1 && dot(this_drhodt, last_drhodt) < 0) {
+ c *= -1;
+ }
+ }
auto write_line = [&]() {
std::stringstream out;
+ auto rhotot = rhovec.sum();
+ double z0 = rhovec[0] / rhotot;
using id = IsochoricDerivatives<decltype(model)>;
- out << z0 << "," << rhovec[0] << "," << rhovec[1] << "," << T << "," << rhotot * model.R(rhovec / rhovec.sum()) * T + id::get_pr(model, T, rhovec) << "," << c << "," << dTdt << "," << drhodT(0) << "," << drhodT(1) << "," << conditions(0) << "," << conditions(1) << std::endl;
+ auto conditions = get_criticality_conditions(model, T, rhovec);
+ out << z0 << "," << rhovec[0] << "," << rhovec[1] << "," << T << "," << rhotot * model.R(rhovec / rhovec.sum()) * T + id::get_pr(model, T, rhovec) << "," << c << "," << conditions(0) << "," << conditions(1) << std::endl;
std::string sout(out.str());
std::cout << sout;
if (ofs.is_open()) {
@@ -353,22 +403,28 @@ struct CriticalTracing {
}
}
- // Flip the sign if the tracing wants to go backwards, or if the first step would yield any negative concentrations
-
- VecType this_drhodt = (c * drhodt).eval();
- VecType step = rhovec + this_drhodt * dt;
- Eigen::ArrayX<bool> negativestepvals = (step < 0).eval();
- if (iter == 0 && negativestepvals.any()) {
- c *= -1;
+ controlled_step_result res;
+ try {
+ res = controlled_stepper.try_step(xprime, x0, t, dt);
}
- else if (iter > 1 && dot(this_drhodt, last_drhodt) < 0) {
- c *= -1;
+ catch(...){
+ break;
+ }
+ if (res != controlled_step_result::success) {
+ // Try again, with a smaller step size
+ iter--;
+ continue;
}
- rhovec += c * drhodt * dt;
- T += c * dTdt * dt;
+ // Call the function again to get drho/dt in order
+ // to cache it
+ auto dxdt = x0;
+ xprime(x0, dxdt, -1.0);
+ auto drhodt = Eigen::Map<Eigen::ArrayXd>(&(dxdt[0]) + 1, dxdt.size() - 1);
+ last_drhodt = c * drhodt;
- z0 = rhovec[0] / rhovec.sum();
+ auto conditions = get_criticality_conditions(model, T, rhovec);
+ auto z0 = rhovec[0] / rhovec.sum();
if (z0 < 0 || z0 > 1) {
break;
}
@@ -381,22 +437,24 @@ struct CriticalTracing {
catch (std::exception& e) {
std::cout << e.what() << std::endl;
}
-
- rhotot = rhovec.sum();
+ auto rhotot = rhovec.sum();
z0 = rhovec[0] / rhotot;
-
if (z0 < 0 || z0 > 1) {
break;
- }
- last_drhodt = c * drhodt;
+ }
+
if (!filename.empty()) {
write_line();
}
+
+ // Calculate some other parameters, for debugging, or scientific interest
using id = IsochoricDerivatives<decltype(model), Scalar, VecType>;
double p = rhotot * model.R(rhovec / rhovec.sum()) * T + id::get_pr(model, T, rhovec);
conditions = get_criticality_conditions(model, T, rhovec);
double splus = id::get_splus(model, T, rhovec);
+
+ // Store the data in a JSON structure
nlohmann::json point = {
{"t", t},
{"T / K", T},
diff --git a/src/tests/catch_test_multifluid.cxx b/src/tests/catch_test_multifluid.cxx
new file mode 100644
index 0000000..226a583
--- /dev/null
+++ b/src/tests/catch_test_multifluid.cxx
@@ -0,0 +1,27 @@
+#include "catch/catch.hpp"
+
+#include "teqp/models/multifluid.hpp"
+#include "teqp/algorithms/critical_tracing.hpp"
+
+TEST_CASE("Confirm failure for missing files","[multifluid]") {
+ CHECK_THROWS(build_multifluid_model({ "BADFLUID" }, "IMPOSSIBLE PATH", "IMPOSSIBLE PATH.json"));
+ CHECK_THROWS(build_multifluid_model({ "BADFLUID" }, "IMPOSSIBLE PATH", "../mycp/dev/mixtures/mixture_binary_pairs.json"));
+}
+
+TEST_CASE("Trace critical locus for nitrogen + ethane", "[crit],[multifluid]")
+{
+ std::string root = "../mycp";
+ const auto model = build_multifluid_model({ "Nitrogen", "Ethane" }, root, root+"/dev/mixtures/mixture_binary_pairs.json");
+
+ for (auto ifluid = 0; ifluid < 2; ++ifluid) {
+ double T0 = model.redfunc.Tc[ifluid];
+ Eigen::ArrayXd rhovec0(2); rhovec0 = 0.0; rhovec0[ifluid] = 1.0 / model.redfunc.vc[ifluid];
+
+ auto tic0 = std::chrono::steady_clock::now();
+ std::string filename = "h";
+ using ct = CriticalTracing<decltype(model), double, Eigen::ArrayXd>;
+ auto j = ct::trace_critical_arclength_binary(model, T0, rhovec0, filename);
+ CHECK(j.size() > 3);
+ auto tic1 = std::chrono::steady_clock::now();
+ }
+}
\ No newline at end of file
--
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