Changeset f6237dd in git for factory/cfModResultant.cc

Timestamp:

Nov 12, 2012, 6:14:16 PM (11 years ago)

Author:

Martin Lee <martinlee84@…>

Branches:

(u'jengelh-datetime', 'ceac47cbc86fe4a15902392bdbb9bd2ae0ea02c6')(u'spielwiese', '0604212ebb110535022efecad887940825b97c3f')

Children:

4f6d994465bf76173207af0e9c819e5b06dbc566

Parents:

1e5c50f82763473c007a2714c91d4ac318709892

git-author:

Martin Lee <martinlee84@web.de>2012-11-12 18:14:16+01:00

git-committer:

Martin Lee <martinlee84@web.de>2012-11-16 13:22:07+01:00

Message:

chg: faster computation of resultants

Conflicts:

	factory/cfModResultant.cc

File:

• factory/cfModResultant.cc (modified) (8 diffs)

factory/cfModResultant.cc

@@ -14 +14 @@
 
 #include "cf_assert.h"
+#include "timing.h"
 
 #include "cfModResultant.h"
@@ -29 +30 @@
 #include "FLINTconvert.h"
 #endif
+
+TIMING_DEFINE_PRINT(fac_resultant_p)
 
 //TODO arrange by bound= deg (F,xlevel)*deg (G,i)+deg (G,xlevel)*deg (F, i)
@@ -327 +330 @@
     return power (B, degAx);
 
+  if (A.isUnivariate() && B.isUnivariate() && A.level() == B.level())
+    return uniResultant (A, B);
+
   CanonicalForm F= A;
   CanonicalForm G= B;
@@ -337 +343 @@
 
   Variable y= Variable (2);
-
-  if (F.isUnivariate() && G.isUnivariate() && F.level() == G.level())
-    return N(uniResultant (F, G));
 
   int i= -1;
@@ -363 +366 @@
     if (H == modResult)
       equalCount++;
+    else
+      equalCount= 0;
 
     count++;
@@ -473 +478 @@
   CanonicalForm resultModP, q (0), newResult, newQ;
   CanonicalForm result;
+  int equalCount= 0;
+  CanonicalForm test, newTest;
+  int count= 0;
   do
   {
@@ -487 +495 @@
     setCharacteristic (p);
 
+    TIMING_START (fac_resultant_p);
     resultModP= resultantFp (mapinto (F), mapinto (G), X, prob);
+    TIMING_END_AND_PRINT (fac_resultant_p, "time to compute resultant mod p: ");
 
     setCharacteristic (0);
 
+    count++;
     if ( q.isZero() )
     {
@@ -501 +512 @@
       q= newQ;
       result= newResult;
-      if (newQ > bound)
-      {
-        result= symmetricRemainder (result, q);
+      test= symmetricRemainder (result,q);
+      if (test != newTest)
+      {
+        newTest= test;
+        equalCount= 0;
+      }
+      else
+        equalCount++;
+      if (newQ > bound || (prob && equalCount == 2))
+      {
+        result= test;
         break;
       }