From 387db2b9b4ccad433d1770dd788125e5f3d18489 Mon Sep 17 00:00:00 2001
From: Pascal <molin.maths@gmail.com>
Date: Fri, 16 Sep 2016 17:07:18 +0200
Subject: [PATCH] add explicit group_dlog_clear

using subgroup and clearing it would have corrupted the dlog pointers
---
 acb_dirichlet.h                       |  1 +
 acb_dirichlet/group_clear.c           | 11 -----------
 acb_dirichlet/group_dlog_precompute.c | 21 +++++++++++++++++++--
 acb_dirichlet/test/t-chars.c          |  2 ++
 doc/source/acb_dirichlet.rst          | 11 +++++++++--
 5 files changed, 31 insertions(+), 15 deletions(-)

diff --git a/acb_dirichlet.h b/acb_dirichlet.h
index 4735fd29..283147d0 100644
--- a/acb_dirichlet.h
+++ b/acb_dirichlet.h
@@ -72,6 +72,7 @@ void acb_dirichlet_group_init(acb_dirichlet_group_t G, ulong q);
 void acb_dirichlet_subgroup_init(acb_dirichlet_group_t H, const acb_dirichlet_group_t G, ulong h);
 void acb_dirichlet_group_clear(acb_dirichlet_group_t G);
 void acb_dirichlet_group_dlog_precompute(acb_dirichlet_group_t G, ulong num);
+void acb_dirichlet_group_dlog_clear(acb_dirichlet_group_t G);
 
 /* properties of elements without log */
 
diff --git a/acb_dirichlet/group_clear.c b/acb_dirichlet/group_clear.c
index 125a28ae..9864ad1c 100644
--- a/acb_dirichlet/group_clear.c
+++ b/acb_dirichlet/group_clear.c
@@ -15,17 +15,6 @@
 void
 acb_dirichlet_group_clear(acb_dirichlet_group_t G)
 {
-    slong k;
-
-    for (k = 0; k < G->num; k++)
-    {
-        if (G->P[k].dlog != NULL)
-        {
-            dlog_precomp_clear(G->P[k].dlog);
-            flint_free(G->P[k].dlog);
-        }
-    }
-
     flint_free(G->P);
     flint_free(G->generators);
     flint_free(G->PHI);
diff --git a/acb_dirichlet/group_dlog_precompute.c b/acb_dirichlet/group_dlog_precompute.c
index 292efc7f..2ab1daf6 100644
--- a/acb_dirichlet/group_dlog_precompute.c
+++ b/acb_dirichlet/group_dlog_precompute.c
@@ -18,11 +18,28 @@ acb_dirichlet_prime_group_dlog_precompute(acb_dirichlet_prime_group_struct * P,
     dlog_precomp_modpe_init(P->dlog, P->g, P->p, P->e, P->pe.n, num);
 }
 
-
 void
 acb_dirichlet_group_dlog_precompute(acb_dirichlet_group_t G, ulong num)
 {
     slong k;
     for (k = 0; k < G->num; k++)
-        acb_dirichlet_prime_group_dlog_precompute(&G->P[k], num);
+    {
+        if (G->P[k].dlog == NULL)
+            acb_dirichlet_prime_group_dlog_precompute(&G->P[k], num);
+    }
+}
+
+void
+acb_dirichlet_group_dlog_clear(acb_dirichlet_group_t G)
+{
+    slong k;
+    for (k = 0; k < G->num; k++)
+    {
+        if (G->P[k].dlog != NULL)
+        {
+            dlog_precomp_clear(G->P[k].dlog);
+            flint_free(G->P[k].dlog);
+            G->P[k].dlog = NULL;
+        }
+    }
 }
diff --git a/acb_dirichlet/test/t-chars.c b/acb_dirichlet/test/t-chars.c
index c5a4cbd0..a650aa95 100644
--- a/acb_dirichlet/test/t-chars.c
+++ b/acb_dirichlet/test/t-chars.c
@@ -140,6 +140,8 @@ int main()
 
             }
 
+            acb_dirichlet_group_dlog_clear(G);
+
             acb_dirichlet_char_clear(chi);
             acb_dirichlet_char_clear(chi2);
             acb_dirichlet_conrey_clear(x);
diff --git a/doc/source/acb_dirichlet.rst b/doc/source/acb_dirichlet.rst
index 5ec85d71..40661bf7 100644
--- a/doc/source/acb_dirichlet.rst
+++ b/doc/source/acb_dirichlet.rst
@@ -76,11 +76,12 @@ logarithms.
 .. function:: void acb_dirichlet_subgroup_init(acb_dirichlet_group_t H, const acb_dirichlet_group_t G, ulong h)
 
    Given an already computed group *G* mod `q`, initialize its subgroup *H*
-   defined mod `h\mid q`. Precomputed discrete log tables are kept.
+   defined mod `h\mid q`. Precomputed discrete log tables are inherited.
 
 .. function:: void acb_dirichlet_group_clear(acb_dirichlet_group_t G)
 
-    Clears *G*.
+    Clears *G*. Remark this function does *not* clear the discrete logarithm
+    tables stored in *G* (which may be shared with another group).
 
 .. function:: void acb_dirichlet_group_dlog_precompute(acb_dirichlet_group_t G, ulong num)
 
@@ -89,6 +90,12 @@ logarithms.
 
     If *num* gets very large, the entire group may be indexed.
 
+.. function:: void acb_dirichlet_group_dlog_clear(acb_dirichlet_group_t G, ulong num)
+
+   Clear discrete logarithm tables in *G*. When discrete logarithm tables are
+   shared with subgroups, those subgroups must be cleared before clearing the
+   tables.
+
 Conrey elements
 -------------------------------------------------------------------------------