Add SAD guess

src/scf/guess/guess.hpp

@@ -20,16 +20,23 @@
 namespace scf::guess {
 
 DECLARE_MODULE(Core);
+DECLARE_MODULE(SAD);
 
 inline void load_modules(pluginplay::ModuleManager& mm) {
     mm.add_module<Core>("Core guess");
+    mm.add_module<SAD>("SAD guess");
 }
 
 inline void set_defaults(pluginplay::ModuleManager& mm) {
     mm.change_submod("Core guess", "Build Fock operator",
                      "Restricted One-Electron Fock Op");
     mm.change_submod("Core guess", "Guess updater",
                      "Diagonalization Fock update");
+
+    mm.change_submod("SAD guess", "Build Fock operator",
+                     "Restricted One-Electron Fock Op");
+    mm.change_submod("SAD guess", "Guess updater",
+                     "Diagonalization Fock update");
 }
 
 } // namespace scf::guess

src/scf/guess/sad.cpp

@@ -0,0 +1,101 @@
+/*
+ * Copyright 2025 NWChemEx-Project
+ *
+ * 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.
+ */
+
+#include "guess.hpp"
+
+namespace scf::guess {
+namespace {
+const auto desc = R"(
+SAD Guess
+---------
+
+TODO: Write me!!!
+)";
+}
+
+using rscf_wf        = simde::type::rscf_wf;
+using density_t      = simde::type::decomposable_e_density;
+using pt             = simde::InitialGuess<rscf_wf>;
+using fock_op_pt     = simde::FockOperator<density_t>;
+using update_pt      = simde::UpdateGuess<rscf_wf>;
+using initial_rho_pt = simde::InitialDensity;
+
+using simde::type::tensor;
+
+// TODO: move to chemist?
+struct NElectronCounter : public chemist::qm_operator::OperatorVisitor {
+    NElectronCounter() : chemist::qm_operator::OperatorVisitor(false) {}
+
+    void run(const simde::type::T_e_type& T_e) { set_n(T_e.particle().size()); }
+
+    void run(const simde::type::V_en_type& V_en) {
+        set_n(V_en.lhs_particle().size());
+    }
+
+    void run(const simde::type::V_ee_type& V_ee) {
+        set_n(V_ee.lhs_particle().size());
+        set_n(V_ee.rhs_particle().size());
+    }
+
+    void set_n(unsigned int n) {
+        if(n_electrons == 0)
+            n_electrons = n;
+        else if(n_electrons != n) {
+            throw std::runtime_error("Deduced a different number of electrons");
+        }
+    }
+
+    unsigned int n_electrons = 0;
+};
+
+MODULE_CTOR(SAD) {
+    description(desc);
+    satisfies_property_type<pt>();
+    add_submodule<fock_op_pt>("Build Fock operator");
+    add_submodule<update_pt>("Guess updater");
+    add_submodule<initial_rho_pt>("SAD Density");
+}
+
+MODULE_RUN(SAD) {
+    const auto&& [H, aos] = pt::unwrap_inputs(inputs);
+
+    // Step 1: Build Fock Operator with zero density
+    auto& initial_rho_mod = submods.at("SAD Density");
+    const auto& rho       = initial_rho_mod.run_as<initial_rho_pt>(H);
+    auto& fock_op_mod     = submods.at("Build Fock operator");
+    const auto& f         = fock_op_mod.run_as<fock_op_pt>(H, rho);
+
+    // Step 2: Get number of electrons and occupations
+    simde::type::cmos cmos(tensor{}, aos, tensor{});
+    NElectronCounter visitor;
+    H.visit(visitor);
+    auto n_electrons = visitor.n_electrons;
+    if(n_electrons % 2 != 0)
+        throw std::runtime_error("Assumed even number of electrons");
+
+    typename rscf_wf::orbital_index_set_type occs;
+    using value_type = typename rscf_wf::orbital_index_set_type::value_type;
+    for(value_type i = 0; i < n_electrons / 2; ++i) occs.insert(i);
+
+    rscf_wf zero_guess(occs, cmos);
+    auto& update_mod = submods.at("Guess updater");
+    const auto& Psi0 = update_mod.run_as<update_pt>(f, zero_guess);
+
+    auto rv = results();
+    return pt::wrap_results(rv, Psi0);
+}
+
+} // namespace scf::guess

tests/cxx/integration_tests/guess/sad.cpp

@@ -0,0 +1,53 @@
+/*
+ * Copyright 2024 NWChemEx-Project
+ *
+ * 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.
+ */
+
+#include "../integration_tests.hpp"
+
+using simde::type::tensor;
+using shape_type   = tensorwrapper::shape::Smooth;
+using cmos_type    = simde::type::cmos;
+using density_type = simde::type::decomposable_e_density;
+using rscf_wf      = simde::type::rscf_wf;
+using occ_index    = typename rscf_wf::orbital_index_set_type;
+
+using pt             = simde::InitialGuess<rscf_wf>;
+using initial_rho_pt = simde::InitialDensity;
+
+using tensorwrapper::operations::approximately_equal;
+
+TEMPLATE_LIST_TEST_CASE("SAD", "", test_scf::float_types) {
+    using float_type     = TestType;
+    using allocator_type = tensorwrapper::allocator::Eigen<float_type>;
+
+    auto mm  = test_scf::load_modules<float_type>();
+    auto aos = test_scf::h2_aos();
+    auto H   = test_scf::h2_hamiltonian();
+    auto rt  = mm.get_runtime();
+
+    auto mod = mm.at("SAD guess");
+    auto psi          = mod.template run_as<pt>(H, aos);
+    const auto& evals = psi.orbitals().diagonalized_matrix();
+
+    occ_index occs{0};
+    allocator_type alloc(rt);
+    shape_type shape_corr{2};
+    auto pbuffer = alloc.construct({-0.498376, 0.594858});
+    tensor corr(shape_corr, std::move(pbuffer));
+
+    REQUIRE(psi.orbital_indices() == occs);
+    REQUIRE(psi.orbitals().from_space() == aos);
+    REQUIRE(approximately_equal(corr, evals, 1E-6));
+}

tests/cxx/integration_tests/integration_tests.hpp

@@ -16,6 +16,7 @@
 
 #pragma once
 #include "../test_scf.hpp"
+#include <chemcache/chemcache.hpp>
 #include <integrals/integrals.hpp>
 #include <nux/nux.hpp>
 #include <scf/scf.hpp>
@@ -31,6 +32,7 @@ pluginplay::ModuleManager load_modules() {
     scf::load_modules(mm);
     integrals::load_modules(mm);
     nux::load_modules(mm);
+    chemcache::load_modules(mm);
 
     mm.change_submod("SCF Driver", "Hamiltonian",
                      "Born-Oppenheimer approximation");
@@ -44,13 +46,16 @@ pluginplay::ModuleManager load_modules() {
 
     mm.change_submod("Loop", "Overlap matrix builder", "Overlap");
 
+    mm.change_submod("SAD guess", "SAD Density", "sto-3g SAD density");
+
     if constexpr(!std::is_same_v<FloatType, double>) {
         mm.change_input("Evaluate 2-Index BraKet", "With UQ?", true);
         mm.change_input("Evaluate 4-Index BraKet", "With UQ?", true);
         mm.change_input("Overlap", "With UQ?", true);
         mm.change_input("ERI4", "With UQ?", true);
         mm.change_input("Kinetic", "With UQ?", true);
         mm.change_input("Nuclear", "With UQ?", true);
+        mm.change_input("sto-3g atomic density matrix", "With UQ?", true);
     }
 
     return mm;