Sagemath 9.2 Product function Bug

bug
product

asked 2021-02-17 02:00:44 +0100

updated 2021-02-17 02:10:17 +0100

In sagemath 9.2 the product function have a bug in multiplication.

var('q')
var('jt')
((q^(2/3)+q**(2/5))*(product(1 -q**jt, jt, 1 , 31) * q**(1 /24 ))).expand()

returned a result with leading series to be (Both wrong in the powers and the coefficients )

...+ 2*q^(121/24) - 2*q^(49/24) - 2*q^(25/24) + 2*q^(1/24)

while

((q^(2/3)+q**(2/5))*(product(1 -q**jt, jt, 1 , 31) * q**(1 /24 )).expand()).expand()

returned a result with leading series to be

...+ q^(653/120) - q^(65/24) - q^(293/120) - q^(41/24) - q^(173/120) + q^(17/24) + q^(53/120)

Notice that both

((q^(2/3)+q**(2/5))*(product(1 -q**jt, jt, 1 , 30) * q**(1 /24 ))).expand()
((q^(2/3)+q**(2/5))*(product(1 -q**jt, jt, 1 , 30) * q**(1 /24 )).expand()).expand()

returned a result with leading series to be

...+ q^(653/120) - q^(65/24) - q^(293/120) - q^(41/24) - q^(173/120) + q^(17/24) + q^(53/120)

edit retag flag offensive close merge delete

Comments

Note that :

sage: foo=((q^(2/3)+q**(2/5))*(product(1 -q**jt, jt, 1 , 31) * q**(1 /24 ))).expand()
sage: bar=((q^(2/3)+q**(2/5))*(prod([1-q^u for u in (1..31)]) * q**(1 /24 ))).expand()
sage: bool(foo==bar)
True

In other words, the use of the Python prod on the explicit extension of your factors gives the same result as the (evaluated) symbolic product. The problem may be somewhere else.

Emmanuel Charpentier ( 2021-02-17 10:32:40 +0100 )edit

add a comment

sage: var("q, jt") (q, jt) sage: A=q^(2/3)+q**(2/5) sage: B=product(1 -q**jt, jt, 1 , 31)*q**(1 /24 ) sage: bool((A*B).expand()==(A*B.expand()).expand()) False sage: (((A*B).expand())/(A*B.expand()).expand()).factor() 2*q^(1/24)/(q^(17/24) + q^(53/120))

Comments

this is an oldish bug, same happens with almost 3 years old https://github.com/pynac/pynac/releas...

Dima ( 2021-02-17 13:36:15 +0100 )edit

add a comment

Your Answer

Please start posting anonymously - your entry will be published after you log in or create a new account.

Sagemath 9.2 Product function Bug

Comments

1 Answer

Comments

Your Answer

Question Tools

Stats

Related questions

Sagemath 9.2 Product function Bug edit

Comments

1 Answer

Comments

Your Answer

Question Tools

Stats

Related questions

Sagemath 9.2 Product function Bug