I have to apply the SMA* algorithm for the labyrinth problem in Python. I found just this PDF: pdfSMA, but it didn't help me too much.
I tried to resolve it, but I didn't manage. Any implementation for this algorithm in Python would help me.
The original description of SMA* from the original AIMA book is flawed. If you implement it as described it may not work. The issue is that you need to preserve the ordering of children and be sure to explore unexplored children before re-exploring old children.
Felner introduced the idea of collapse and restore macros which can be very helpful in understanding SMA*. I suggest looking at that paper and then using a similar approach to implement the algorithm.
But, also know that the recent A*+IDA* algorithm may be a better approach than SMA*. (Not much help if it is an assignment.)
I have found this somewhere over internet and I'm being curious how it's done that this lib is so smooth (even on my slow PC) and what's more important what algorithm had been used to create that 'sticky' effect. Maybe you know where can I learn about that kind of algorithms?
Thanks for help in advance :)
This visualisation uses a force layout. The algorithm is described in the documentation and you can of course have a look at the source code yourself. You can also have a look at the source of this particular visualisation to see what parameters etc were used, but a better way to get started would be to have a look at the documentation and examples on the D3 website.
I have an application that will hold a set of images in a SQLDatabase and then the user will take a photo and I want to be able to match it with an image in the database.
I have no idea where to start, can anyone help? point me in the right direction?
Thanks
Start by checking out OpenCV.
The problem you are trying to solve is not exactly trivial though. It is an area of ongoing research and none of the algorithms are perfect (in fact they're all far from perfect, IMO).
Good luck!
Start with OpenCV and understand that this is a non-trivial task.
http://opencv.willowgarage.com/wiki/
Good luck.
I was searching google for something and saw the post that some one needed a piece of software in which he can take a sheet of material- and that he can maximize the cuts.
he needs to be able to enter the width and the length of the roll.
Then he would enter the sizes of cuts that he would need. After all the sizes are entered, the software would tell me how to cut the material so that he can achieve maximum efficiency.
Possible???
is there some AI involved?
This is referred to as a packing problem and is an important area of research in combinatorics, a field of mathematics. See http://en.wikipedia.org/wiki/Packing_problem
Yes it is possible and done in manufacturing. The simple way to think about it is you try any combination the computer can think of and take the one that is best (brute force). Basically it pretends to make a cut and then sees what is left, makes another pretend cut and sees what is left until the material is gone and then it tries them in a different location/order.
It is an optimization problem and there are many solutions out there.
http://en.wikipedia.org/wiki/Optimization_problem A wiki link that will lead you to many hours of reading.
This is entirely possible. It's just an optimization layout problem. I can't help you code it, but it's definitely possible and I suspect strongly that there are even efficient algorithms to do it.
I would imagine this problem has already solved a long time ago, when people did the calculations rather than software. I dont know the name of the problem, but i have seen that solving the optimal way to pack circlse in a box is a well known mathematical problem.
This is indeed 2D bin packing. As for software, take a look at Drools Planner (open source, java).
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When I am stuck with a problem:
I search Google for code snippets.
I look at isolating the problem, so that I can better explain it to others in order to get answers.
What search techniques do you use to find the solution to your problem?
I started asking questions in Stack Overflow.
What other techniques or methods do you follow, to fix the problem more quickly?
Go and do something else. No, really. I've found that putting the problem away in the back of my mind helps. I can't count the number of times I thought of a great solution to something I've been working on when I was working on something else, or watching TV, or eating. It seems your brain is still working on the problem in the background.
If that fails to solve your problem, try talking to someone. You'd be surprised how often others can give solutions to your problem that are so simple you'd facepalm.
Well there's:
Google
Google
Google
Stack Overflow
Google
Google
Maybe a book if I have one.
Seriously, I started (hobby) programming in the 1980s and even into the mid 90s you had to know things and have a technical library. Then Google came along and it's easier to Google something than it is to look up (bookmarked!) API documentation (Google "java stringbuilder" will get me there faster than navigating will) let alone an actual book (electronic or paper).
Most problems you're trying to solve have been solved before. Many times.
The rest of debugging comes down to decomposition, possibly unit testing (which is related to decomposition) and verifying your assumptions.
By "decomposition", I mean that your solution is structured in such a way that small pieces can be individually tested and readily understood. If you have a 7000 line method you're (probably) doing something wrong.
Understanding what assumptions you've made is key too so you can verify them. For example, when I started with PHP I wrote a piece of code like this:
$fields = $_SESSION["fields"]; // $fields is an associative array
$fields["blah"] = "foo";
and I was scratching my head trying to figure out why it didn't work (the array wasn't being updated next time I queried $_SESSION). I came from a Java background where you might do this:
Map fields = (Map)httpSession.get("fields");
fields.put("blah", "foo");
and that would most definitely work. PHP however copies the array. A working solution is to use references:
$fields =& $_SESSION["fields"]; // $fields is an associative array
$fields["blah"] = "foo";
or simply:
$_SESSION["fields"]["blah"] = "foo";
The last thing I'll say about debugging and writing robust code in general is to understand the boundaries of your solution. By this I mean if you're implementing a linked list then the boundary conditions will revolve around when the list is empty.
Explain the problem to a colleague, or write it down to describe it. That will makes you think a different way, from a different perspective. In order to be more accurate, and to describe the context of the problem, you'll step back, get a higher level view of the problem, you may find out think you overlooked something that is actually important.
Sometimes, you even find the explanation before ending your description.
My best friend for many years has been to jump on my bike and go home. Just getting away from the keyboard has solved many problems over the years for me.
If the problem lasts to the end of the day, I try and consciously lock the problem away for solving before I go to sleep.
I realise this sounds a bit out there, but it has been very common in my experience that I'll wake up with at least an alternate approach to the problem, if not the full-on solution. The idea is not to stress about it - but actively decide to solve it over night. That way you can go to sleep without worry.
I think eating well, regular exercise and good sleep are huge contributors to the problem-solving process.
Usually I'll try nut out the problem for a few hours or so, trying different things writing it on paper, making diagrams. If none of that works I'll usually work through the following options.
Put a sticky note on my monitor and keep going with something else
Glance at the note through out the next few hours to keep the problem in the back of my mind
Google for similar problems and the methods used
Consult a co-worker or a friend
Ask on a forum such as stackoverflow
Give up and design the problem away or design a way around the problem so it can be dealt with some other time and stick a TODO note at the site of said workaround
Don't forget Google Code Search
It's often best to clear your head by doing something other than programming for a little while. See this answer for an example - I did it while struggling with a particularly thorny bug, and when I came back to the problem I solved it in about a minute.
Usually I try to solve it until I go to sleep.. Sometimes I write on paper what the code is doing and then I divide it in pieces; I try to know how the variables of the program change when it's running.
Try solving a much smaller version of the problem first and see how you get on with that.
Once you've done that the bigger problem won't look so scary.
Ask yourself: is solving this particular tricky problem really important to what you doing?
For the purposes of your application (or whatever the big picture is) is there a similar but easier problem that you could address to accomplish broadly the same thing.
Normally, I would get pen and paper and try to work out the details of the problem there. If that doesn't help, Google. Failing that, I'd do something else for a while, or ask online. Worked for me so far.
The fact you are stuck might be a 'code-smell'. Suggesting that their is something wrong with the design or approach somewhere else. Try to put your finger on what's causing this and fix this instead.
When you come back to your problem it might no longer exist.
One more time, browse thru what I think might be relevant, then take nap.
There are two other answers which mention sleeping or napping, but this deserves more emphasis. It is now known that there's SERIOUS machinery in there which goes to work when you sleep. Google (( CBS SCIENCE SLEEP )) will get you to a great free video.
If I can't figure out how to solve the real problem, I try to consider a simplified version of the problem. To take a simple example: I recently had the problem of finding a set of shipping routes to get an item from point A to point B, when there is not necessarily a direct route from A to B, but there might be an A to C and then C to B, or A to C, C to D, and then D to B. (I'm sure the airlines and railroads do this all the time.) That was fairly complex, so I tried looking first at the simple case: a direct A to B. That was easy. Then consider how I'd handle it with one stop along the way. Then consider two stops. At that point I was able to see the pattern to a solution.
Solutions to a simplified version of the problem may end up being a part of the bigger solution, with some additional complexity wrapped around them. But even if not, the exercise of solving the easier problem often gives you ideas on how to solve the real problem.
The main techniques I use (should be followed in order so that you can reuse what you have done in previous steps to be more efficient):
Define your issue: Try to clearly define what's the problem, and what's expected. See 2 to help you.
Collect data about the bug: Log everything: your attempts, the expected result, the observed result. This will avoid the need to redo several times the same tests (because your mind cannot memorize it all), and probably help you see the bigger picture.
Reduce your problem. This is true in general for any abstract modelling of natural phenomenons, but it's even more true of programming, because programs are very complex entities. You should try to reduce your code to a minimal program that reproduces your issue. Automated tools exist.
Talk to someone: several anecdotes affirm than about 2/3 of the bugs are resolved just by talking about it. See the Helpful Teddy Bear anecdote. If you have previously reduced your program to a minimal program, and have a clear definition of your issue, both will be useful to your explanation.
Reach for collaborative help: search on Google and on StackOverflow, and post if you can't find anything that answers your problem (but first see 1, you must have a clear definition of your problem).
As you can see, I put the collaborative help as the last step, because you should only ask for help after you have clearly defined your issue and tried to reduce the problem and fix it by yourself. If you reach for collaborative help before having tried the previous steps, you will either end up with a poor help or figure it out by yourself as soon as you have posted.
Also you can be interested in the Coursera Software Debugging course, which also describes several automated debugging methods.
Go to the toilet.
You move, so your brain gets oxygen.
You relax, so you focus on other things.
Peeing for innovation! :)