Validate PPCG H operator input

Author: cheerly-pku

source/source_hsolver/diago_ppcg.h

@@ -114,7 +114,8 @@ class DiagoPPCG
         return row + col * ld;
     }
 
-    void validate_input(const T* psi_in, const Real* eigenvalue_in,
+    void validate_input(const HPsiFunc& hpsi_func,
+                        const T* psi_in, const Real* eigenvalue_in,
                         const std::vector<double>& ethr_band,
                         const Real* prec) const;
 

source/source_hsolver/ppcg/diago_ppcg_diag.hpp

@@ -18,7 +18,7 @@ double DiagoPPCG<T, Device>::diag(const HPsiFunc& hpsi_func,
     n_band_ = nband;
     n_dim_ = dim;
 
-    validate_input(psi_in, eigenvalue_in, ethr_band, prec);
+    validate_input(hpsi_func, psi_in, eigenvalue_in, ethr_band, prec);
     spsi_func_ = spsi_func;
 
     // Allocate working storage.

source/source_hsolver/ppcg/diago_ppcg_ops.hpp

@@ -42,11 +42,14 @@ DiagoPPCG<T, Device>::DiagoPPCG(const Real& diag_thr,
 // =============================================================================
 template <typename T, typename Device>
 void DiagoPPCG<T, Device>::validate_input(
+    const HPsiFunc& hpsi_func,
     const T* psi_in,
     const Real* eigenvalue_in,
     const std::vector<double>& ethr_band,
     const Real* prec) const
 {
+    if (!hpsi_func)
+        throw std::invalid_argument("PPCG: H operator is empty.");
     if (psi_in == nullptr || eigenvalue_in == nullptr)
         throw std::invalid_argument("PPCG: psi/eigenvalue pointer is null.");
     if (prec == nullptr)

source/source_hsolver/test/diago_ppcg_test.cpp

@@ -269,6 +269,28 @@ TEST_F(DiagoPPCGDiagonalTest, ConjugateGradientFallback)
         << "Diagonal CG fallback: too many iterations";
 }
 
+TEST_F(DiagoPPCGDiagonalTest, EmptyHOperatorThrows)
+{
+    std::vector<T>    psi_run = psi;
+    std::vector<Real> eval(nband, 0.0);
+
+    hsolver::DiagoPPCG<T, hsolver::base_device::DEVICE_CPU> solver(
+        /* diag_thr = */ 1e-12,
+        /* max_iter = */ 50,
+        /* sbsize   = */ 3,
+        /* rr_step  = */ 3,
+        /* gamma_g0 = */ false,
+        hsolver::PpcgStrategy::BLOCK_SUBSPACE
+    );
+
+    hsolver::DiagoPPCG<T, hsolver::base_device::DEVICE_CPU>::HPsiFunc h_op;
+    EXPECT_THROW(
+        solver.diag(h_op, nullptr, ld, nband, n_dim,
+                    psi_run.data(), eval.data(), ethr, prec.data()),
+        std::invalid_argument
+    );
+}
+
 TEST(DiagoPPCGLeadingDimensionTest, BlockSubspaceWithPadding)
 {
     const int n_dim = 5;