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## reduce-algebra-developers

 [Reduce-algebra-developers] erratic solve/groesolve From: Jarmo Hietarinta - 2012-09-12 10:52:05 ```This is distilled from an actual problem. Suppose I have already solved 6 equations using groesolve and now add the 7th: res3:={c16=(c11**2*c6)/(a11*cp11), b11=(bp11*cp11)/c11, b6=c11/cp11, a6=cp11/c11, ap11=(a11*ap16*cp11)/c11, apzz=(a11*cp11*cpzz)/(c11*cp6), - ap16*cp11*cp6 + c11*c6}; I now try to solve this with reduce as follows: Reduce (Free CSL version), 14-Apr-09 ... 1: off nat; 2: load groebner; 3: groebmonfac:=0; groebmonfac := 0\$ 4: 4: res3:={c16=(c11**2*c6)/(a11*cp11), 4: b11=(bp11*cp11)/c11, 4: b6=c11/cp11, 4: a6=cp11/c11, 4: ap11=(a11*ap16*cp11)/c11, 4: apzz=(a11*cp11*cpzz)/(c11*cp6), 4: - ap16*cp11*cp6 + c11*c6}; res3 := {c16=(c11**2*c6)/(a11*cp11), b11=(bp11*cp11)/c11, b6=c11/cp11, a6=cp11/c11, ap11=(a11*ap16*cp11)/c11, apzz=(a11*cp11*cpzz)/(c11*cp6), - ap16*cp11*cp6 + c11*c6}\$ %then groesolve tilts without giving any result at all; same with solve: 5: solve(res3); Unknowns: {a11,a6,ap11,ap16,apzz,b11,b6,bp11,c11,c16,c6,cp11,cp6,cpzz} 6: groesolve(res3); % but if after this I change 1 variable in the set: 7: sub(bp11=bp10,res3); {c16=(c11**2*c6)/(a11*cp11), b11=(bp10*cp11)/c11, b6=c11/cp11, a6=cp11/c11, ap11=(a11*ap16*cp11)/c11, apzz=(a11*cp11*cpzz)/(c11*cp6), - ap16*cp11*cp6 + c11*c6}\$ % then groesolve can solve it, but uses 12 seconds! 8: groesolve ws; {{a6=cp11/c11, ap11=(a11*c6)/cp6, apzz=(a11*cp11*cpzz)/(c11*cp6), b11=(bp10*cp11)/c11, b6=c11/cp11, c16=(c11**2*c6)/(a11*cp11), ap16=(c11*c6)/(cp11*cp6)}}\$ 9: showtime; Time: 12139 ms plus GC time: 220 ms What goes wrong? regards, Jarmo Hietarinta ---------------------------------------------------------------------------------- Prof. Jarmo Hietarinta Department of Physics and Astronomy University of Turku, FIN-20014 Turku, Finland mobile: +358-40-722 5685 ---------------------------------------------------------------------------------- ```
 Re: [Reduce-algebra-developers] erratic solve/groesolve From: Rainer Schöpf - 2012-09-12 17:30:12 ```Thanks for reporting this. Your copy of REDUCE is rather old; an up-to-date version still exhibits the problem, but gives the error message +++ Error attempt to take car of an atom: failed I think I have found the cause of the problem; it seems to be an incorrect treatment of one particular case in the algorithm. As to why it works when you rename one of the variables, I suspect that this renaming leads to a different internal ordering of the variables when computing the Groebner base. I have a preliminary solution; I'll get back to you after I have verified that it is indeed correct. Regards, Rainer ______________________________________________________________________________ On Wed, 12 Sep 2012 at 10:36 -0000, Jarmo Hietarinta wrote: > This is distilled from an actual problem. > > Suppose I have already solved 6 equations using groesolve and now add the 7th: > > res3:={c16=(c11**2*c6)/(a11*cp11), > b11=(bp11*cp11)/c11, > b6=c11/cp11, > a6=cp11/c11, > ap11=(a11*ap16*cp11)/c11, > apzz=(a11*cp11*cpzz)/(c11*cp6), > - ap16*cp11*cp6 + c11*c6}; > > I now try to solve this with reduce as follows: > > Reduce (Free CSL version), 14-Apr-09 ... > > 1: off nat; > > 2: load groebner; > > 3: groebmonfac:=0; > > groebmonfac := 0\$ > > 4: > 4: res3:={c16=(c11**2*c6)/(a11*cp11), > 4: b11=(bp11*cp11)/c11, > 4: b6=c11/cp11, > 4: a6=cp11/c11, > 4: ap11=(a11*ap16*cp11)/c11, > 4: apzz=(a11*cp11*cpzz)/(c11*cp6), > 4: - ap16*cp11*cp6 + c11*c6}; > > res3 := {c16=(c11**2*c6)/(a11*cp11), > b11=(bp11*cp11)/c11, > b6=c11/cp11, > a6=cp11/c11, > ap11=(a11*ap16*cp11)/c11, > apzz=(a11*cp11*cpzz)/(c11*cp6), > - ap16*cp11*cp6 + c11*c6}\$ > > %then groesolve tilts without giving any result at all; same with solve: > > 5: solve(res3); > > Unknowns: {a11,a6,ap11,ap16,apzz,b11,b6,bp11,c11,c16,c6,cp11,cp6,cpzz} > 6: groesolve(res3); > > % but if after this I change 1 variable in the set: > > 7: sub(bp11=bp10,res3); > > {c16=(c11**2*c6)/(a11*cp11), > b11=(bp10*cp11)/c11, > b6=c11/cp11, > a6=cp11/c11, > ap11=(a11*ap16*cp11)/c11, > apzz=(a11*cp11*cpzz)/(c11*cp6), > - ap16*cp11*cp6 + c11*c6}\$ > > % then groesolve can solve it, but uses 12 seconds! > > 8: groesolve ws; > > {{a6=cp11/c11, > ap11=(a11*c6)/cp6, > apzz=(a11*cp11*cpzz)/(c11*cp6), > b11=(bp10*cp11)/c11, > b6=c11/cp11, > c16=(c11**2*c6)/(a11*cp11), > ap16=(c11*c6)/(cp11*cp6)}}\$ > > 9: showtime; > > Time: 12139 ms plus GC time: 220 ms > > What goes wrong? > > regards, Jarmo Hietarinta > > ---------------------------------------------------------------------------------- > Prof. Jarmo Hietarinta > Department of Physics and Astronomy > University of Turku, FIN-20014 Turku, Finland > mobile: +358-40-722 5685 > ---------------------------------------------------------------------------------- > ------------------------------------------------------------------------------ > Live Security Virtual Conference > Exclusive live event will cover all the ways today's security and > threat landscape has changed and how IT managers can respond. Discussions > will include endpoint security, mobile security and the latest in malware > threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ > _______________________________________________ > Reduce-algebra-developers mailing list > Reduce-algebra-developers@... > https://lists.sourceforge.net/lists/listinfo/reduce-algebra-developers > Rainer Schöpf```
 Re: [Reduce-algebra-developers] erratic solve/groesolve From: Rainer Schöpf - 2012-10-04 16:54:30 ```Sorry for the delay in responding. The error you reported is corrected in the latest sources. To access this version, you need to download from the source repository; more information is here: http://reduce-algebra.com/downloading.htm We intend to release a new prepackaged version of REDUCE soon, but I cannot commit to a definite date right now. Rainer Schöpf ```