Wikipedia:Reference desk/Archives/Mathematics/2016 April 20
| Mathematics desk | ||
|---|---|---|
| < April 19 | << Mar | April | May >> | April 21 > |
| Welcome to the Wikipedia Mathematics Reference Desk Archives |
|---|
| The page you are currently viewing is an archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages. |
April 20 edit
Miminum Flow Problem edit
Hi, I know that maximum flow problem is in . But what about the minimum flow problem? Is it in too? Is it ? 213.8.204.61 (talk) 10:28, 20 April 2016 (UTC)
- Isn't the minimum flow zero? -- SGBailey (talk) 16:07, 20 April 2016 (UTC)
- For minimum flow problems, maximum flow problem#Definition is expanded so that in addition to a capacity defined for each edge, there is also a nonnegative lower bound of flow defined for each edge, and if a least one such lower bound is positive, then the minimum flow will not be zero.
- Algorithms for minimum flows (Computer Science Journal of Moldova, vol.9, no.3(27), 2001) gives such a definition and claims to "present a generic preflow algorithm and several implementations of it, that solve the minimum flow problem in O(n2m) time." -- ToE 21:24, 20 April 2016 (UTC)
- I was asked to implement a reduction of this to standard max flow. Since I was told it was possible (and eventually found out how), the problem at hand clearly is in P.--Jasper Deng (talk) 07:37, 24 April 2016 (UTC)
- Thank you!! 213.8.204.72 (talk) 17:38, 25 April 2016 (UTC)
Octavan primes edit
I just noticed a Wikipedia article called Quartan prime, which means a prime number of the form a^4 + b^4. How many octavan primes are known?? (You should be able to guess what I mean easily here!) (Note: n has to be a power of 2 for a^n + b^n to be prime.) Georgia guy (talk) 17:12, 20 April 2016 (UTC)
- Some are shown at https://oeis.org/A006686. —Wavelength (talk) 17:22, 20 April 2016 (UTC)