Changeset ac3fcca in git for factory/facFqBivarUtil.cc

Timestamp:

Jan 27, 2012, 10:29:46 AM (12 years ago)

Author:

Martin Lee <martinlee84@…>

Branches:

(u'spielwiese', 'fe61d9c35bf7c61f2b6cbf1b56e25e2f08d536cc')

Children:

5583e1b42c274997413efbdad76b287132f8fff4

Parents:

5335ba2fd90593fc954dfc07320a6302bf956290

git-author:

Martin Lee <martinlee84@web.de>2012-01-27 10:29:46+01:00

git-committer:

Oleksandr Motsak <motsak@mathematik.uni-kl.de>2012-02-10 14:16:43+01:00

Message:

chg: computation of G*oldQ

File:

• factory/facFqBivarUtil.cc (modified) (1 diff)

factory/facFqBivarUtil.cc

@@ -483 +483 @@
   CanonicalForm logDeriv;
 
-  CanonicalForm bufF= F;
-  CanonicalForm oldF= mulMod2 (G, oldQ, xToL);
-  bufF -= oldF;
-  bufF= div (bufF, xToOldL);
+  CanonicalForm bufF;
+  if ((oldL > 100 && l - oldL < 50) || (oldL < 100 && l - oldL < 30))
+  {
+    bufF= F;
+    CanonicalForm oldF= mulMod2 (G, oldQ, xToL);
+    bufF -= oldF;
+    bufF= div (bufF, xToOldL);
+  }
+  else
+  {
+    //middle product style computation of [G*oldQ]^{l}_{oldL}
+    CanonicalForm G3= div (G, xToOldL);
+    CanonicalForm Up= mulMod2 (G3, oldQ, xToLOldL);
+    CanonicalForm xToOldL2= power (x, oldL/2);
+    CanonicalForm G2= mod (G, xToOldL);
+    CanonicalForm G1= div (G2, xToOldL2);
+    CanonicalForm G0= mod (G2, xToOldL2);
+    CanonicalForm oldQ1= div (oldQ, xToOldL2);
+    CanonicalForm oldQ0= mod (oldQ, xToOldL2);
+    CanonicalForm Mid= mulMod2 (G1, oldQ1, xToLOldL);
+    //computation of Low might be faster using a real middle product?
+    CanonicalForm Low= mulMod2 (G0, oldQ1, xToOldL)+mulMod2 (G1, oldQ0, xToOldL);
+    Low= div (Low, xToOldL2);
+    Up += Mid + Low;
+    bufF= div (F, xToOldL);
+    bufF -= Up;
+  }
 
   q= newtonDiv (bufF, G, xToLOldL);