smart lindep handling in LASSI kernel

my_pyscf/lassi/lassi.py

@@ -5,6 +5,7 @@
 from mrh.my_pyscf.lassi import op_o1
 from mrh.my_pyscf.lassi.citools import get_lroots
 from pyscf import lib, symm
+from pyscf.scf.addons import canonical_orth_
 from pyscf.lib.numpy_helper import tag_array
 from pyscf.fci.direct_spin1 import _unpack_nelec
 from itertools import combinations, product
@@ -418,16 +419,16 @@ def _eig_block (las, e0, h1, h2, ci_blk, nelec_blk, rootsym, soc, orbsym, wfnsym
     # Error catch: linear dependencies in basis
     try:
         e, c = linalg.eigh (ham_blk, b=ovlp_blk)
-    except linalg.LinAlgError as e:
+    except linalg.LinAlgError as err:
         ovlp_det = linalg.det (ovlp_blk)
         lc = 'checking if LASSI basis has lindeps: |ovlp| = {:.6e}'.format (ovlp_det)
-        lib.logger.info (las, 'Caught error %s, %s', str (e), lc)
+        lib.logger.info (las, 'Caught error %s, %s', str (err), lc)
         if ovlp_det < LINDEP_THRESH:
-            err_str = ('LASSI basis appears to have linear dependencies; '
-                       'double-check your state list.\n'
-                       '|ovlp| = {:.6e}').format (ovlp_det)
-            raise RuntimeError (err_str) from e
-        else: raise (e) from None
+            x = canonical_orth_(ovlp_blk, thr=LINDEP_THRESH)
+            xhx = x.conj ().T @ ham_blk @ x
+            e, c = linalg.eigh (xhx)
+            c = x @ c
+        else: raise (err) from None
     return e, c, s2_blk
 
 def make_stdm12s (las, ci=None, orbsym=None, soc=False, break_symmetry=False, opt=1):