Re: [sage-support] Re: Bug:Different results when using preparse
I tried on a different machine with Sage Version 6.5, Release Date: 2015-02-17 and I get the same behaviour described in the original post. Where parsing a string and evaluating returns different results than using the resulted sage expression. On Thursday, 12 March 2015 17:00:45 UTC-4, Nils Bruin wrote: On Thursday, March 12, 2015 at 1:00:28 PM UTC-7, M M wrote: Thanks so much for all the efforts for making sage output consistent results for the numerical approximation. However, the main problem I had was the fact that Sage returns different answers when I preparse the string of the same sage expression as in the examples of the original post. I was not able to replicate that behaviour on a recent build. -- You received this message because you are subscribed to the Google Groups sage-support group. To unsubscribe from this group and stop receiving emails from it, send an email to sage-support+unsubscr...@googlegroups.com. To post to this group, send email to sage-support@googlegroups.com. Visit this group at http://groups.google.com/group/sage-support. For more options, visit https://groups.google.com/d/optout.
Re: [sage-support] Re: Bug:Different results when using preparse
Thanks so much for all the efforts for making sage output consistent results for the numerical approximation. However, the main problem I had was the fact that Sage returns different answers when I preparse the string of the same sage expression as in the examples of the original post. On Wednesday, 11 March 2015 17:18:12 UTC-4, William wrote: On Wed, Mar 11, 2015 at 2:07 PM, Dima Pasechnik dim...@gmail.com javascript: wrote: On Wednesday, 11 March 2015 16:44:32 UTC, William wrote: On Wed, Mar 11, 2015 at 9:35 AM, Dima Pasechnik dim...@gmail.com wrote: On 2015-03-11, Nils Bruin nbr...@sfu.ca wrote: On Wednesday, March 11, 2015 at 2:46:25 AM UTC-7, Dima Pasechnik wrote: I tried this integral directly in Maxima, and taking bfloat of it outputs nonsense. I have noticed before that bfloats aren't infectious enough: operations on bfloats can easily result in a normal double. I think there are ways to convince maxima to use bfloats more pervasively. Perhaps a global precision setting somewhere? I wish there was a more accessible full implementation of Risch algorithm... This is a rational function, so a first calculus course would already teach you the relevant part of the Risch algorithm. It's a little more tricky to Risch, as implemented in Axiom, does not do factorisation (i.e. no partial fractions). In this example at least it produces much nicer looking antiderivative, no huge integers. http://axiom-wiki.newsynthesis.org/ExampleIntegration Dima For what it's worth, here's how to mostly do that Axiom session, but in a SageMathCloud worksheet... https://cloud.sagemath.com/projects/4a5f0542-5873-4eed-a85c-a18c706e8bcd/files/support/2015-03-11-093745-axiom-integral.sagews here is a better version (all the stuff works): https://cloud.sagemath.com/projects/bb6fd6ca-6304-4dda-be31-bd2dd5eb3d98/files/support/2015-03-11-093745-axiom-integral.sagews Thanks! I replaced mine by yours. William Dima William get an ostensibly real-valued function as an antiderivative. Anyway, sympy produces a reasonable-looking antiderivative. Interestingly, we have: sage: I=integral(x/(x^3-x+1), x, 1, 2, algorithm='sympy') sage: RIF(I) TypeError: unable to simplify to a real interval approximation The offending subexpression seems to be: sage: A=(299838966359964800*69^(5/6)*2^(2/3) - 1151508116605*69^(2/3)*2^(1/3)*(25*sqrt(69) + 207)^(1/3) - 99785894223312000*sqrt(69)*(25*sqrt(69) + 207)^(2/3) + 2271318237097115625*69^(1/3)*2^(2/3) - 99785894223312000*69^(1/6)*2^(1/3)*(25*sqrt(69) + 207)^(1/3) - 497728835949744*9522^(1/3)*(25*sqrt(69) + 207)^(1/3) - 828883890137982336*(25*sqrt(69) + 207)^(2/3) + 219331275901257879*276^(1/3))^(QQ(-1)) sage: RIF(A) TypeError: unable to simplify to a real interval approximation Note the *rational* exponent -1. If that's an integer there's no problem. Using RealIntervalField(200) has the same problem. Using RealField(...) seems to work fine. -- You received this message because you are subscribed to the Google Groups sage-support group. To unsubscribe from this group and stop receiving emails from it, send an email to sage-support...@googlegroups.com. To post to this group, send email to sage-s...@googlegroups.com. Visit this group at http://groups.google.com/group/sage-support. For more options, visit https://groups.google.com/d/optout. -- William (http://wstein.org) -- You received this message because you are subscribed to the Google Groups sage-support group. To unsubscribe from this group and stop receiving emails from it, send an email to sage-support...@googlegroups.com javascript:. To post to this group, send email to sage-s...@googlegroups.com javascript:. Visit this group at http://groups.google.com/group/sage-support. For more options, visit https://groups.google.com/d/optout. -- William (http://wstein.org) -- You received this message because you are subscribed to the Google Groups sage-support group. To unsubscribe from this group and stop receiving emails from it, send an email to sage-support+unsubscr...@googlegroups.com. To post to this group, send email to sage-support@googlegroups.com. Visit this group at http://groups.google.com/group/sage-support. For more options, visit https://groups.google.com/d/optout.
[sage-support] Bug:Different results when using preparse
I get different results from Sage when I try to get a numerical approximation for an expression and if I use evaluate a preparse of the string. I get different results on different versions of sage as well. Here are samples: -- | Sage Version 5.3, Release Date: 2012-09-08 | | Type notebook() for the browser-based notebook interface.| | Type help() for help.| -- sage: eval(preparse(numerical_approx(integral(x/(x^3-x+1), x, 1, 2 0.132008722884722 sage: numerical_approx(integral(x/(x^3-x+1), x, 1, 2)) 0.132008722884722 sage: A = integral(x/(x^3-x+1), x, 1, 2) sage: A_str = str(A) sage: eval(preparse(numerical_approx(+A_str +))) -0.393296585552547 sage: ┌┐ │ Sage Version 6.5, Release Date: 2015-02-17 │ │ Type notebook() for the browser-based notebook interface.│ │ Type help() for help.│ └┘ sage: eval(preparse(numerical_approx(integral(x/(x^3-x+1), x, 1, 2 1.45943044687563 sage: numerical_approx(integral(x/(x^3-x+1), x, 1, 2)) 1.45943044687563 sage: A = integral(x/(x^3-x+1), x, 1, 2) sage: sage: A_str = str(A) sage: sage: eval(preparse(numerical_approx(+A_str +))) 0.159046901967485 sage: ┌┐ │ Sage Version 6.2, Release Date: 2014-05-06 │ │ Type notebook() for the browser-based notebook interface.│ │ Type help() for help.│ └┘ sage: eval(preparse(numerical_approx(integral(x/(x^3-x+1), x, 1, 2 1.64714767119638 sage: numerical_approx(integral(x/(x^3-x+1), x, 1, 2)) 1.64714767119638 sage: A = integral(x/(x^3-x+1), x, 1, 2) sage: A_str = str(A) sage: eval(preparse(numerical_approx(+A_str +))) 0.162416510011260 sage: On the Notebook on the cloud it gives me the following error although the version is the same as one of the versions I tried locally version() 'Sage Version 6.5, Release Date: 2015-02-17' numerical_approx(integral(x/(x^3-x+1), x, 1, 2)) Error in lines 1-1 Traceback (most recent call last): File /projects/f700a2f3-7f30-4b47-9f18-e0309eb8c48c/.sagemathcloud/sage_server.py, line 875, in execute exec compile(block+'\n', '', 'single') in namespace, locals File , line 1, in module File string, line 1, in module File /usr/local/sage/sage-6.5/local/lib/python2.7/site-packages/sage/misc/functional.py, line 1298, in numerical_approx return x._numerical_approx(prec, algorithm=algorithm) File sage/symbolic/expression.pyx, line 4861, in sage.symbolic.expression.Expression._numerical_approx (build/cythonized/sage/symbolic/expression.cpp:27184) x = self._convert(kwds) File sage/symbolic/expression.pyx, line 1034, in sage.symbolic.expression.Expression._convert (build/cythonized/sage/symbolic/expression.cpp:7790) cdef GEx res = self._gobj.evalf(0, kwds) ValueError: power::eval(): division by zero -- You received this message because you are subscribed to the Google Groups sage-support group. To unsubscribe from this group and stop receiving emails from it, send an email to sage-support+unsubscr...@googlegroups.com. To post to this group, send email to sage-support@googlegroups.com. Visit this group at http://groups.google.com/group/sage-support. For more options, visit https://groups.google.com/d/optout.
[sage-support] Strange behaviour in a simple function
Hi I have written very simple function, which code I paste below. The thing is that it produces completely unexpected results. I paste them below. Please let me know if this is a bug or I just do something completely wrong. I change in tests only the modulus M. def MLCG_S(B,M,N,x0): x = x0 L = [] for i in range(1,N): x = Mod(B*x, M) #MLCG(B,M,x) print x==B print (B-M) print (x-M) print M-B print M-x return L; 2^31-1 Invocation: LCG_16807 = MLCG_S(16807,2^31-1,2,1); Result: True -2147466840 16807 2147466840 2147466840 ___2^20-1 Invocation:LCG_16807 = MLCG_S(16807,2^20-1,2,1); Result: True -1031768 16807 1031768 1031768 ___2^10-1 Invocation:LCG_16807 = MLCG_S(16807,2^10-1,2,1); Result: True 15784 439 -15784 584 Above, not only the first two differences are different, but also the last two differences are different! Cheers -- To post to this group, send email to sage-support@googlegroups.com To unsubscribe from this group, send email to sage-support+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/sage-support URL: http://www.sagemath.org
