Révision 205

pobysoPythonSage/src/sageSLZ/sageSLZ.sage (revision 205)
1138 1138 
      Check if an element (argument) of the domain of function (function)
1139 1139 
      yields a HTRN case (rounding to next) for the target precision
1140 1140 
      (as impersonated by targetRF) for a given accuracy (targetAccuracy).
1141
1142 
      The strategy is:
1143 
      - compute the image at high (quasi-exact) precision;
1144 
      - round it to nearest to precision;
1145 
      - round it to exactly to (precision+1), the computed number has two
1146 
        midpoint neighbors;
1147 
      - check the distance between these neighbors and the quasi-exact value;
1148 
        - if none of them is closer than the targetAccuracy, return False,
1149 
        - else return true.
1150 
      - Powers of two are a special case when comparing the midpoint in
1151 
        the 0 direction..
1141 1152 
    """
1142 1153 
    ## Arguments filtering.
1143 1154 
    ## TODO: filter the first argument for consistence.
......
1175 1186 
    #print "QuasiEx value :", quasiExactValue.n(prec=250).str(base=2)
1176 1187 
    #print "Lower midpoint:", \
1177 1188 
    #  roundedValuePrecPlusOnePrev.n(prec=targetPlusOnePrecRF.prec()).str(base=2)
1178 
    ## Begining of the general case : check with the midpoint with
1189 
    ## Make quasiExactValue = 0 a special case to move it out of the way.
1190 
    if quasiExactValue == 0:
1191 
        return False
1192 
    ## Begining of the general case : check with the midpoint of
1179 1193 
    #  greatest absolute value.
1180 1194 
    if quasiExactValue > 0:
1181 1195 
        if abs(quasiExactRF(roundedValuePrecPlusOneNext) - quasiExactValue) <\
......
1191 1205 
            #print "Upper midpoint:", \
1192 1206 
            #  roundedValuePrecPlusOneNext.n(prec=targetPlusOnePrecRF.prec()).str(base=2)
1193 1207 
            return True
1194 
    else:
1208 
    else: # quasiExactValue < 0, the 0 case has been previously filtered out.
1195 1209 
        if abs(quasiExactRF(roundedValuePrecPlusOnePrev) - quasiExactValue) < \
1196 1210 
           binadeCorrectedTargetAccuracy:
1197 1211 
            #print "Too close to the upper midpoint: ", \
......
1376 1390 
    return ccComplientRowsList
1377 1391 
# End slz_reduce_and_test_base
1378 1392 

  		





  
  1393
  
    
def slz_resultant(poly1, poly2, elimVar):


  		





  
  1394
  
    
    """


  		





  
  1395
  
    
    Compute the resultant for two polynomials for a given variable


  		





  
  1396
  
    
    and return the (poly1, poly2, resultant) if the resultant


  		





  
  1397
  
    
    is not 0.


  		





  
  1398
  
    
    Return () otherwise.


  		





  
  1399
  
    
    """


  		





  
  1400
  
    
    polynomialRing0    = poly1.parent()


  		





  
  1401
  
    
    resultantInElimVar = poly1.resultant(poly2,polynomialRing0(elimVar))


  		





  
  1402
  
    
    if resultantInElimVar.is_zero():


  		





  
  1403
  
    
        return None


  		





  
  1404
  
    
    else:


  		





  
  1405
  
    
        return resultantInElimVar


  		





  
  1406
  
    
# End slz_resultant.


  		





  
  1407
  
    
#


  		





  1379
  1408
  
    
def slz_resultant_tuple(poly1, poly2, elimVar):


  		





  1380
  1409
  
    
    """


  		





  1381
  1410
  
    
    Compute the resultant for two polynomials for a given variable


  		












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