Rasori

I've been trying to get this post up, but I've been travelling: I've actually been thinking about Xittenn's suggestion quite a bit and I'm trying to determine if it really is optimized. Say each customer has a list of Vehicle references (presumably primary key values for the corresponding vehicles). To then pull up the information for those vehicles still requires a query on the entire database of vehicle entries, does it not? Whereas before the query was (in pseudocode) "get all VEHICLES where OWNER is Owner_Name," now isn't it "get all VEHICLES where PRIMARY_KEY is one of [PK_Values]" ? It seems a massive memory improvement over storing the entire vehicle, but does it truly save performance? I think, basically, this question comes down to: are databases generally optimized for Primary Key checks? If (as I believe) yes, then just how speedy is this optimized query?

Hi all, I'm trying to find out how to establish when to optimize for processor usage versus memory usage. In the application I'm working on it's not actually a big deal (not large-scale enough to worry about) but I'm curious how it's decided for more critical tasks. The situation is something like this: Vehicle X has Customer Y, where Y is the Owner of X. It would be possible for each Customer Y to have a list of all Vehicles they own stored within them. Which would be preferred: the increased memory usage of having each Customer Y list all Vehicles they own, or the increased processing time required to go through all Vehicles and return a list of all Vehicles where Vehicle.Owner is Customer Y? In my application, with a locally-stored database that isn't remarkably large, I intend to just go ahead and use the extra memory. Both usage cases (needing to select one of the customer's vehicles in order to start an invoice or similar, or needing to find the owner of a certain vehicle currently on the premises) are quite likely to crop up, so I figure it would be nice to be able to approach the problem equally effectively from either direction. Is there a best-practice to determine how to make a decision like this under more critical circumstances? Thanks!

Haha you guys take the fun out of passing time with idle thought. Of course I could use two different screwdrivers, but that eliminates the project aspect of it all. The concept is to enable someone like me who does a lot of tinkering, sometimes with sensitive electronics and other times just pulling stuff apart, and who gets attached to that particularly comfortable ratcheting screwdriver, to get both options with low hassle. The end result would, in my mind, be a single ratcheting screwdriver, with one set of tips, which could be both magnetic or non-magnetic depending on requirements. I do like the idea of the already-electric screwdriver, but tearing one of those apart is a bit beyond what I had in mind. It sounds like, if I really do want to go this route, standard batteries are the way to go rather than capacitors, and there's no point working out any dynamo-based option. At least when dealing with batteries I'll be able to handle the power considerations more easily on my own.

Hey all, I've been toying with the idea of an electromagnetic screwdriver, allowing for the convenience of a magnetic tip and the sensitivity of a standard tip. Yeah, forgive me, I'm bored. Anyway, toying with the idea I've been wondering about power. I'm sure I can make an electromagnet with batteries, and given the low mass of the screws, probably (haven't gotten around to testing it yet) even with just one AA or similar. Worst-case, I've been reading that D-cells are quite useful in these things. What I've been wondering is if it would be possible to use a capacitor bank. I know they're usually used for high power for short periods, but I also know that they can be used for other purposes. For example, I have a squeeze dynamo LED flashlight which doesn't need to be squeezed every time I want to turn it on, and from wikipedia I can see that these are sometimes capacitor-powered. In the end, my preference would be similar to this--a battery-free option. I'd like it not to be obnoxious: squeeze the handle once for around a minute (or more) of magnetic awesomeness, which hopefully would last through a standard working session without needing to recharge if left unused. Or, if a crank dynamo, turn the crank a few times, perhaps? I'm not familiar enough with the electronics to know if this might be possible without simply building it and testing, as I can't get a value for the resistance of the coil. I'm not asking anyone else to do that, but if people know offhand that it would be possible, I'd be more willing to splurge on the components to build it (I'm a college student with no money for pizza, let alone components which won't work), and if people know offhand it wouldn't be, I'll stop following this little path. Thanks for any advice!

Cool. I've got some work to do for school, but I'll probably work on transferring it over tonight. I'll let you know if anything goes wrong. Merged post follows: Consecutive posts mergedThe importing of my blog was quick and painless. Only complaint is that it imported my tags as categories . That said, I'm liking the features I didn't know I didn't have, and I'll be able to change from categories to tags in the near future. Thanks, SFN!

What version of Wordpress is this using? I'd happily transfer my blog over (presuming programming counts as science enough) but I've been posting daily for just over a month now on Blogger and I'm finding that only Wordpress 2.2 and above can import from the current Blogger.

Hi all. I'm working on a little simulation-like game, basically an excel spreadsheet on steroids that relies on player interaction and creativity for the fun bits. Ignoring whether or not the game itself would be fun, I've come across a couple of questions. If you need more information, feel free to either ask for it here or check out the pertinent posts on my blog to see if you can see where I'm going. First question is about JButtons. I have a series of buttons, standard "add one," "fill," "subtract one," and "empty" buttons. They're to be labeled simply with "+", "+ +", "-", and "- -" respectively. The problem is it seems that the JButton is set to have a default requirement for distance-from-edge for the text. In other words, it looks like it needs 15 pixels from the edge to the start of the string, 10 pixels per character, and another 15 pixels from the end of the string to the last edge. If it doesn't have this minimum, Java has been truncating my string down to "..." for whatever reason, despite the fact that I'm almost certain "+" is shorter than "..." physically. I've worked these numbers out on the premise that the minimum size for a properly displayed add-one button is 40 pixels, and the fill button (with the space between the plus signs) must be 60 pixels. I'm trying to get it down to have both of the buttons simply be little squares with these strings in them. Is there no way to change these defaults? I'm thinking the only method is to make a custom graphic for the button, which I'll do eventually but it takes a while for me because I'm good at coding, not graphics Second question is about databases. I'm planning on hooking this up, via JDO, to a database structure. I've found a convenient e-book, available for free online here, that is really helping me to understand what I need to do on my end, and everything tells me there's not much that needs to be done to set up the database for it. But I have the problem that everything assumes I understand the basics of Java database connectivity and setup. While I have researched a good deal of MySQL back before I settled on JDO, and know some of this, I would like a nice guide for the initial setup of a JDO-compatible database, if you've got any suggestions. Thanks! Thanks for any and all help, in advance!

The electricity would be used to power a very powerful laser or something like that. I'm not entirely sure how they create black holes, but allegedly they already happen in labs on occasion, it mostly has to be scaled up slightly. In terms of the radiation, the suggestion was to use a parabolic mirror I believe--anything already going away from the ship provides thrust just like any other engine, and anything going towards the ship bounces back and also provides thrust.

Aha. That, my friends, takes the cake. Simple yet perfect (and blatantly missed by me). Thank you very much!

The temporary table won't be deleted on the client logging out? That was the understanding the link gave me. If not, sweet and thank you, but if it does I may need to fall back on manual labor (or some jury-rigged scripting, which is really what programming is about to me anyway ). It does certainly seem that a view is not going to work. I'll do some more research on temporary tables.

I read about this recently in NewScientist (no claims are being made by me on validity of any source). From what I read it sounded feasible and certainly interesting, but it's one of those things where "feasible" means that I understood what was being said, not that I verified the facts he used. The biggest drawback was the power needed to create the black hole. Something on the order of a gigantic solar panel pretty close to the sun being able to produce a large enough power source once every 3 years? Still, more feasible than travelling the stars with the technology we're currently using.

Hmm... A useful tool but I don't think it's going to work for what I'm looking at (it is, however, entirely possible that what I'm looking for isn't going to have a nice solution). I'm thinking more of something that can be initiated, say, on Saturday, and then will have the same values through to Friday night, where it will be updated to new values. [Edit: this would be through potentially multiple iterations of a client logging in and out, hence why the temporary table doesn't seem to fit my needs] In honesty, because of the scale of what I'm looking at (read: very small), it may be better to just manually make the tables I need each week.

I'm just kind of playing around with programming, I've gotten a relatively solid grasp on Java and eventually decided what I actually wanted to do with it. Then I realized that, for my program I need a database. SQL has been the best option so far, but I need to find out if I can make a view that doesn't refresh when its referenced tables are updated. Alternatively, if I could make a table that is based off of the values of another table (only at the time of creation), that would also be acceptable. The basic concept is to create a view that allows a user to see selected pieces of a table they don't normally have access to. Preferably, I'd like a specific procedure to be the only way to refresh the view's values, though it's acceptable if I'd have to outright drop the view and create a new one every time I want to update it. I can easily see why this may not have been implemented in SQL, but nonetheless I was hoping there was some way I could do it. If you've got any ideas, please let me know! (I'm using MySQL and InnoDB but all I've gotten so far is a rough outline so it's still early enough for me to change (foreign keys are a must for the database, as a note, and preferably I'd like something free/open-source)).

I'm actually specifically unclear about the start-up. According to a brief google search, yes, latch is what I'm talking about. Null is my own terminology, I guess (I've been playing with programming too much lately). Basically, when a system containing an S-R Latch is first started (batteries freshly inserted and everything), I don't understand how the NAND gates have any output at all, as they're based off of two inputs and only receiving one. The second input to the NAND gate is inherently dependent on the past values of the other input, of which there are none. As I think about it more and more I slowly come up with my own reasoning--the best idea I've had so far is that a two-input NAND gate with one of the inputs being neither logic 0 or logic 1 (logic 0 inherently has some reading, it's not absolutely empty if I understand correctly) thinks of itself as simply an inverter on the one valid input. Is that right?

I've been doing some digital electronics in my studies lately, and I'm just not getting this part. Well, rather, I can do all the work just fine, I'm just not understanding something that my lecturer claims is unimportant. I'm sure many of you know what it is, but to make the problem I have clear I'm going to explain: S NAND (NOT)Q = A = Q R NAND Q = B = (NOT)Q They both seem simple enough, but I'm not getting how it /starts/. On start-up, S and R are defined, but I can't fathom how S[or R] NAND (NULL) gives a value at all. My best guess would be to set S and R = logic 0 to start with, so that regardless of (NULL) the NAND would be logic 1, but A and B can't be the same value by definition of the SR Flip-Flop. Is it acceptable to break that rule for this initialization or is something else going on here?