For what applications of the traveling salesman problem, does visiting each city at most once truely matter?

Traditionally, the traveling salesman problem has you visit a city at least once and at most once.

However, if you were an actual traveling salesman, you would want the least cost route to visit each city at least once, and you wouldn’t be bothered visiting a city 2, 3, or more times. For given city, you might stop and hawk your wares only once, and on subsequent visits, only drive through the city without stopping.

Consider an undirected graph having a city incident to exactly two edges. The cost on one of these edges is only 10 units, while the cost on the other is 99,999,999,999. If you insist on visiting each city at most once, then you are forced to incur the cost of the high cost edge. However, if you allow yourself to visit cities multiple times, then you simply leave the way you came in (on the low cost edge). The low cost edge leads you back to a city you’ve passed through before.

The traveling salesman problem is highly contrived for an actual traveling salesman. I want to give students an application for which there’s a real incentive to visit each city at most once. For what applications is visiting each city a critical aspect of the problem?

Media keys, xfce4-notifyd stops working if headphones are unplugged once after startup, ubuntu 18.04

Following this post:

I was able to get media keys working again by enabling xfce4-notifyd. Brightness and media keys work.

The problem is, if I unplug headphones even once (from either an external sound card, or internal sound card jack), the ability to use media keys stops. The keys won’t change the sound for the headphones. Brightness and other keys still work.

The only resolution is a computer restart to get the notify / volume change working again on the headphones.

Restarting the notify service, nor pulse audio changes this.

18.04 xubunu doesn’t seem to have xfce-volumed or xfce-mixer packages anymore. The new functionality is also fairly frustrating with all of these small bugs with sound.

Any idea how to fix media keys so that even if headphones are re-plugged in, the system will listen for them?

What is the adjective for “only one of many can be active at once”?

I have a toolbar in which some or all tools are in an only-one-active-at-once state. That is, if there are tools A+B+C, if A is active and I activate B, A becomes inactive.

What’s the proper term for that?

The only word I can think of right now is “tabbed”, but in the context I’m developing, not all tools have the visual metaphor of a tab (but some do!) which could lead to confusion.

“Modal” also came to mind, but the active state does not restrict interaction with other tools, so I don’t believe it’s the right word.

When using a spellcasting archetype, do you take the Basic Spellcasting feat multiple times or once?

The rules for Basic Spellcasting state:

Basic Spellcasting Feat: Available at 4th level, these feats grant a 1st-level spell slot. At 6th level, they grant you a 2nd-level spell slot. At 8th level, they grant you a 3rd-level spell slot. Archetypes refer to these benefits as the “basic spellcasting benefits.”

If you take this feat at 4th level, do you have to take it again at 6th level in order to get the 2nd-level spell slot? Or do you just automatically get it and you are free to choose another feat at 6th level? (I don’t know if it is even possible to take feats more than once.)

Furthermore, what if you want to delay your multiclassing, and you dont take Basic Spellcasting until level 6. Do you get a 1st-level or a 2nd-level spell slot? Or both?

This whole wording is very unclear to me.

Is there a balancing issue giving a Wizard a wand capable of casting Illusory Script once per day?

Wizard expressed a desire for a magical wand that could cast the ritual spell Illusory Script without burning a spell slot/ritual slot. I though about giving a wand that can cast the spell once per day. Seems relatively fair for a magical item but not sure if there are any balance implications.

Would an item that prevents death once be overpowered?

I am a DM running Tomb of Annihilation. I am toying with the idea of giving one of my level 5 players an item that prevents death, just once, and then breaks. Note that I do not mean dropping to 0 hit points, but rather actually dying. This is different from death ward. In other words, if the player is to die instantaneously through some mishap or fails his death saves, this item will prevent them from dying just that once.

I like the idea of doing this because an item that gives death ward once would break as soon as the player is about to be knocked unconscious or hit 0 HP for any reason, which isn’t very infrequent. I think this item is particularly interesting in this campaign.

How powerful would an item like this be? I’d like it to be comparable to a +2 weapon or a +2 armor, or a Necklace of Prayer Beads, or a Gem of Seeing.

Stop googlebot crawling URL more than once?

I have a site that usually creates a few thousand pages a day, which don’t change after they have been created. Recently my dedicated server has crashed due to googlebot crawling the site too often. According to the search console, many days googlebot crawls the site tens of thousands of times a day, indicating they keep crawling pages they already crawled. I am aware I can limit the googlebot crawl rate, but is it possible to force googlebot to crawl a page ONCE and ONCE only?

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Writing value to a column only once on list item creation

Using just SharePoint 2010 and InfoPath (with no access to SharePoint Designer or workflows) can the following be achieved?

List Schema (Simplified):

  1. Action – Text Field
  2. Current Target Date – Date Field
  3. Original Target Date – Date Field


  1. Use an InfoPath form for entry, only presenting the user with “Action” and “Current Target Date” to populate.
  2. On record creation the value in “Current Target Date” is also written to “Original Target Date”
  3. Any further updates to “Current Target Date” would not change “Original Target Date”.

Thanks in advance for any help/advise provided.

SharePoint 2010 – Group by two columns at once

I’d like to group a view on two columns at the same time. The first column contains a serial number. The second column, Related To, is a lookup pointing to the Serial Number column. What I’m looking for is a way to group the view so that any items with EITHER a serial number or a matching value in the Related To column are grouped together within the view.


Item     Direction     SN     Related To Hiya     Incoming      123     This     Incoming      234 Is       Outgoing      345    123 An       Outgoing      456    234 Example  Outgoing      567    123 

The result of this would be something like the following:

+ 123     Hiya     Is     Example + 234     This     An 

For now I’m working under the assumption that Incoming items have a serial number only, while Outgoing will have both SN and Related To filled in. I’m assuming SPD is needed to get something like this to happen. Do you have ideas on how to make this happen?