Re: [sage-support] evaluation of polynomials mod 8
Thanks! On Tuesday, September 27, 2022 at 3:02:25 PM UTC+1 Kwankyu wrote: > This bug is tracked now in > > https://trac.sagemath.org/ticket/34591 > > On Tuesday, September 27, 2022 at 6:31:39 PM UTC+9 wdjo...@gmail.com > wrote: > >> On Tue, Sep 27, 2022 at 4:46 AM John Cremona wrote: >> > >> > Am I doing something stupid here, or is this a bug? >> > >> > sage: R = Integers(8) >> > sage: RXY. = R[] >> > sage: F = X^3-X^2*Y+X*Y^2+Y^3 >> > sage: F([4,2]) >> > 6 >> > sage: 4^3-4^2*2+4*2^2+2^3 >> > 56 >> > sage: (4^3-4^2*2+4*2^2+2^3) % 8 >> > 0 >> > >> >> Even after coercion it doesn't evaluate in ZZ/8ZZ: >> >> sage: ZZ8 = IntegerModRing(8) >> sage: R. = PolynomialRing(ZZ8, "x,y") >> sage: f = x^3-x^2*y+x*y^2+y^3 >> sage: x0 = ZZ8(4) >> sage: y0 = ZZ8(2) >> sage: x0^3-x0^2*y0+x0*y0^2+y0^3 >> 0 >> sage: f(x0,y0) >> 6 >> sage: f(4,2) >> 6 >> >> > >> > Why does F not evaluate to 0 mod 8 at X=4, Y=2? Rather obviously, each >> > of the terms in F(4,2) is 0 mod 8. >> > >> > John >> > >> > -- >> > 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 view this discussion on the web visit >> https://groups.google.com/d/msgid/sage-support/CAD0p0K5hXexw5J20gstKUOXxzWdP2a2OTRbKmUtAyG41ySSR-A%40mail.gmail.com >> . >> > -- 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 view this discussion on the web visit https://groups.google.com/d/msgid/sage-support/a3bf46f4-f359-476d-897f-302ac3838cean%40googlegroups.com.
Re: [sage-support] evaluation of polynomials mod 8
This bug is tracked now in https://trac.sagemath.org/ticket/34591 On Tuesday, September 27, 2022 at 6:31:39 PM UTC+9 wdjo...@gmail.com wrote: > On Tue, Sep 27, 2022 at 4:46 AM John Cremona wrote: > > > > Am I doing something stupid here, or is this a bug? > > > > sage: R = Integers(8) > > sage: RXY. = R[] > > sage: F = X^3-X^2*Y+X*Y^2+Y^3 > > sage: F([4,2]) > > 6 > > sage: 4^3-4^2*2+4*2^2+2^3 > > 56 > > sage: (4^3-4^2*2+4*2^2+2^3) % 8 > > 0 > > > > Even after coercion it doesn't evaluate in ZZ/8ZZ: > > sage: ZZ8 = IntegerModRing(8) > sage: R. = PolynomialRing(ZZ8, "x,y") > sage: f = x^3-x^2*y+x*y^2+y^3 > sage: x0 = ZZ8(4) > sage: y0 = ZZ8(2) > sage: x0^3-x0^2*y0+x0*y0^2+y0^3 > 0 > sage: f(x0,y0) > 6 > sage: f(4,2) > 6 > > > > > Why does F not evaluate to 0 mod 8 at X=4, Y=2? Rather obviously, each > > of the terms in F(4,2) is 0 mod 8. > > > > John > > > > -- > > 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 view this discussion on the web visit > https://groups.google.com/d/msgid/sage-support/CAD0p0K5hXexw5J20gstKUOXxzWdP2a2OTRbKmUtAyG41ySSR-A%40mail.gmail.com > . > -- 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 view this discussion on the web visit https://groups.google.com/d/msgid/sage-support/ae69a416-cdb3-4eab-8639-8728152ae3b9n%40googlegroups.com.
Re: [sage-support] evaluation of polynomials mod 8
On Tue, Sep 27, 2022 at 4:46 AM John Cremona wrote: > > Am I doing something stupid here, or is this a bug? > > sage: R = Integers(8) > sage: RXY. = R[] > sage: F = X^3-X^2*Y+X*Y^2+Y^3 > sage: F([4,2]) > 6 > sage: 4^3-4^2*2+4*2^2+2^3 > 56 > sage: (4^3-4^2*2+4*2^2+2^3) % 8 > 0 > Even after coercion it doesn't evaluate in ZZ/8ZZ: sage: ZZ8 = IntegerModRing(8) sage: R. = PolynomialRing(ZZ8, "x,y") sage: f = x^3-x^2*y+x*y^2+y^3 sage: x0 = ZZ8(4) sage: y0 = ZZ8(2) sage: x0^3-x0^2*y0+x0*y0^2+y0^3 0 sage: f(x0,y0) 6 sage: f(4,2) 6 > > Why does F not evaluate to 0 mod 8 at X=4, Y=2? Rather obviously, each > of the terms in F(4,2) is 0 mod 8. > > John > > -- > 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 view this discussion on the web visit > https://groups.google.com/d/msgid/sage-support/CAD0p0K5hXexw5J20gstKUOXxzWdP2a2OTRbKmUtAyG41ySSR-A%40mail.gmail.com. -- 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 view this discussion on the web visit https://groups.google.com/d/msgid/sage-support/CAEQuuAWnh%3Dt97OQDgEx39TMyeYu7UYsih3JmN%2B2cSHSiuCGH5Q%40mail.gmail.com.
Re: [sage-support] evaluation of polynomials mod 8
The iterated subs turns out to be correct sage: F.subs(X=4).subs(Y=2) 0 sage: F.subs(Y=2).subs(X=4) 0 But not the one shot version (which is supposedly equivalent to the evaluation) sage: F.subs(X=4, Y=2) 6 There is definitely something wrong!! Vincent On Tue, 27 Sept 2022 at 10:46, John Cremona wrote: > > Am I doing something stupid here, or is this a bug? > > sage: R = Integers(8) > sage: RXY. = R[] > sage: F = X^3-X^2*Y+X*Y^2+Y^3 > sage: F([4,2]) > 6 > sage: 4^3-4^2*2+4*2^2+2^3 > 56 > sage: (4^3-4^2*2+4*2^2+2^3) % 8 > 0 > > > Why does F not evaluate to 0 mod 8 at X=4, Y=2? Rather obviously, each > of the terms in F(4,2) is 0 mod 8. > > John > > -- > 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 view this discussion on the web visit > https://groups.google.com/d/msgid/sage-support/CAD0p0K5hXexw5J20gstKUOXxzWdP2a2OTRbKmUtAyG41ySSR-A%40mail.gmail.com. -- 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 view this discussion on the web visit https://groups.google.com/d/msgid/sage-support/CAGEwAAm12%3DBhuPHvb2WHzn0HfUJb%3DKcS_E5h8YiZ14Z5MEL9Mw%40mail.gmail.com.
[sage-support] evaluation of polynomials mod 8
Am I doing something stupid here, or is this a bug? sage: R = Integers(8) sage: RXY. = R[] sage: F = X^3-X^2*Y+X*Y^2+Y^3 sage: F([4,2]) 6 sage: 4^3-4^2*2+4*2^2+2^3 56 sage: (4^3-4^2*2+4*2^2+2^3) % 8 0 Why does F not evaluate to 0 mod 8 at X=4, Y=2? Rather obviously, each of the terms in F(4,2) is 0 mod 8. John -- 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 view this discussion on the web visit https://groups.google.com/d/msgid/sage-support/CAD0p0K5hXexw5J20gstKUOXxzWdP2a2OTRbKmUtAyG41ySSR-A%40mail.gmail.com.
