Changeset ea0a9d in git for factory/libfac/charset/alg_factor.cc

Timestamp:

Mar 12, 2014, 2:17:29 PM (10 years ago)

Author:

Martin Lee <martinlee84@…>

Branches:

(u'spielwiese', '873fc1222e995d7cb33f79d8f1792ce418c8c72c')

Children:

ac2c3043b7a7c6fd15fe58c2089a7df5c1daf4ad

Parents:

574650d154909eac6bd00ddec8f7f5ff0828b7a7

git-author:

Martin Lee <martinlee84@web.de>2014-03-12 14:17:29+01:00

git-committer:

Hans Schoenemann <hannes@mathematik.uni-kl.de>2014-03-17 18:31:55+01:00

Message:

chg: compute back substitutions

File:

• factory/libfac/charset/alg_factor.cc (modified) (6 diffs)

factory/libfac/charset/alg_factor.cc

@@ -580 +580 @@
 // K must have more than S elements (->thesis, -> getextension)
 static CFList
-simpleextension(const CFList & Astar, const Variable & Extension, bool& isFunctionField,
+simpleextension(CFList& backSubst, const CFList & Astar,
+                const Variable & Extension, bool& isFunctionField,
                 CanonicalForm & R)
 {
@@ -612 +613 @@
       oldR= R;
       sqrf_norm (i.getItem(), R, Extension, s, g, R);
+
+      backSubst.insert (s);
 
       Off (SW_RATIONAL);
@@ -729 +732 @@
 }
 
+CanonicalForm
+backSubst (const CanonicalForm& F, const CFList& a, const CFList& b)
+{
+  ASSERT (a.length() == b.length() - 1, "wrong length of lists in backSubst");
+  CanonicalForm result= F;
+  Variable tmp;
+  CFList tmp2= b;
+  tmp= tmp2.getLast().mvar();
+  tmp2.removeLast();
+  for (CFListIterator iter= a; iter.hasItem(); iter++)
+  {
+    result= result (tmp+iter.getItem()*tmp2.getLast().mvar(), tmp);
+    tmp= tmp2.getLast().mvar();
+    tmp2.removeLast();
+  }
+  return result;
+}
+
 // the heart of the algorithm: the one from Trager
 #ifndef DEBUGOUTPUT
@@ -740 +761 @@
   CFFList L, Factorlist;
   CanonicalForm R, Rstar, s, g, h, f= F;
-  CFList substlist;
+  CFList substlist, backSubsts;
 
   DEBINCLEVEL(CERR,"alg_factor");
   DEBOUTLN(CERR, "alg_factor: f= ", f);
 
-  //out_cf("start alg_factor:",f,"\n");
-  substlist= simpleextension(Astar, vminpoly, isFunctionField, Rstar);
+  substlist= simpleextension (backSubsts, Astar, vminpoly, isFunctionField, Rstar);
   DEBOUTLN(CERR, "alg_factor: substlist= ", substlist);
   DEBOUTLN(CERR, "alg_factor: minpoly Rstar= ", Rstar);
@@ -768 +788 @@
         h= replacevar (h, alpha, Rstar.mvar());
         h *= bCommonDen(h);
+        h= backSubst (h, backSubsts, Astar);
         h= Prem (h, as);
         L.append (CFFactor (h, i.getItem().exp()));
@@ -846 +867 @@
       {
         g= divide (g, h, Rstarlist);
+        h= backSubst (h, backSubsts, Astar);
         h= Prem (h, as);
         h *= bCommonDen (h);