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| author | J08nY | 2025-03-26 12:12:54 +0100 |
|---|---|---|
| committer | J08nY | 2025-03-26 12:12:54 +0100 |
| commit | f1aa1423b4c1bd138f836a4817cf6f1f53cf7fd5 (patch) | |
| tree | 6b731e54dded8dbe3cfad5b1237276d446f52ecc | |
| parent | dd168eb38724072bd2178f6a251ca2e1486d7be5 (diff) | |
| download | ecgen-f1aa1423b4c1bd138f836a4817cf6f1f53cf7fd5.tar.gz ecgen-f1aa1423b4c1bd138f836a4817cf6f1f53cf7fd5.tar.zst ecgen-f1aa1423b4c1bd138f836a4817cf6f1f53cf7fd5.zip | |
Avoid 0 j invariant in cm_construct_curve.
The selecction between quadratic twist and the curve may not be
enough (there are more twists).
| -rw-r--r-- | src/cm/cm_any.c | 5 |
1 files changed, 5 insertions, 0 deletions
diff --git a/src/cm/cm_any.c b/src/cm/cm_any.c index 6a65571..df50b3a 100644 --- a/src/cm/cm_any.c +++ b/src/cm/cm_any.c @@ -182,12 +182,17 @@ GEN cm_construct_curve(GEN order, GEN d, GEN p, cm_any_roots_t *roots, for (long i = roots->used; i < roots->total; ++i) { roots->used = i + 1; GEN root = gel(roots->roots, i + 1); + if (gequal(root, gen_0)) { + debug_log("skipping root = 0"); + continue; + } debug_log("trying root[%i] = %Pi", i + 1, root); GEN e = ellinit(ellfromj(mkintmod(root, p)), p, 0); pari_CATCH(e_TYPE) { continue; } pari_TRY { checkell(e); }; pari_ENDCATCH{}; + debug_log("ellinit done"); if (ord_prime) { // Easy part, the requested order is prime so |