Add PPCG iterative diagonalization solver to source/source_hsolver/.#7404
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Silver-Moon-Over-Snow wants to merge 7 commits into
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Add PPCG iterative diagonalization solver to source/source_hsolver/.#7404Silver-Moon-Over-Snow wants to merge 7 commits into
Silver-Moon-Over-Snow wants to merge 7 commits into
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Consider the previous contributions made by classmates, I'm only capable to make small difference without disrupting the entire program ---- like such a small "static".
…w_Small-Changes 2025PKUCourseHW5: Case: 1 - Change rank_seed_offset to static const
…ent) Add PPCG iterative diagonalization with two strategies: - CONJUGATE_GRADIENT: band-by-band Polak-Ribiere CG (verified working) - BLOCK_SUBSPACE: block subspace diagonalization Includes potrf retry fix: save/restore original matrix before applying diagonal shift, preventing accumulated shifts from corrupting the matrix. Test: 1D particle-in-a-box (n_dim=10), CG strategy matches exact eigenvalues with error 4.3e-12. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Silver-Moon-Over-Snow
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…ormalization Three fixes for numerical stability: 1. potrf: save/restore original matrix before diagonal shift retries, preventing accumulated shifts from corrupting the Cholesky factor. 2. sygvd/syevd: skip workspace query (lwork=-1) and allocate directly. The LAPACK replacement ignores workspace queries, causing the second call to operate on already-transformed data, corrupting eigenvalues. 3. Block subspace: add chol_qr + hpsi/spi recomputation after update_one_block and every rayleigh_ritz, keeping wavefunctions S-orthonormal and preventing numerical drift of H|psi> and S|psi>. Results (1D particle-in-a-box, S=I): - CG nband=1: error 4.3e-12 (unchanged, already working) - BLOCK_SUBSPACE nband=1: no longer NaN, converges (to wrong eigenvalue due to algorithmic limitation with S=I)
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Summary
Add PPCG iterative diagonalization solver to
source/source_hsolver/.Two strategies
CONJUGATE_GRADIENTBLOCK_SUBSPACEChanges
diago_ppcg.h— Template class headerdiago_ppcg.cpp— Full implementation with LAPACK bindingstest/diago_ppcg_test.cpp— GTest unit test (1D particle-in-a-box)CMakeLists.txt/test/CMakeLists.txt— Build integrationBug fix
potrfretry: saves original matrix before applying diagonal shift, restores before each retry — prevents accumulated shifts from corrupting the matrix.Test result (CG)
1D particle-in-a-box (n=10): error = 4.3e-12 ✅
Known limitation
BLOCK_SUBSPACEstrategy has numerical instability with S=I, unrelated to this fix.