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  • Reverse subarray of an array with O(1)

    - by Babibu
    I have an idea how to implement sub array reverse with O(1), not including precalculation such as reading the input. I will have many reverse operations, and I can't use the trivial solution of O(N). Edit: To be more clear I want to build data structure behind the array with access layer that knows about reversing requests and inverts the indexing logic as necessary when someone wants to iterate over the array. Edit 2: The data structure will only be used for iterations I been reading this and this and even this questions but they aren't helping. There are 3 cases that need to be taking care of: Regular reverse operation Reverse that including reversed area Intersection between reverse and part of other reversed area in the array Here is my implementation for the first two parts, I will need your help with the last one. This is the rule class: class Rule { public int startingIndex; public int weight; } It is used in my basic data structure City: public class City { Rule rule; private static AtomicInteger _counter = new AtomicInteger(-1); public final int id = _counter.incrementAndGet(); @Override public String toString() { return "" + id; } } This is the main class: public class CitiesList implements Iterable<City>, Iterator<City> { private int position; private int direction = 1; private ArrayList<City> cities; private ArrayDeque<City> citiesQeque = new ArrayDeque<>(); private LinkedList<Rule> rulesQeque = new LinkedList<>(); public void init(ArrayList<City> cities) { this.cities = cities; } public void swap(int index1, int index2){ Rule rule = new Rule(); rule.weight = Math.abs(index2 - index1); cities.get(index1).rule = rule; cities.get(index2 + 1).rule = rule; } @Override public void remove() { throw new IllegalStateException("Not implemented"); } @Override public City next() { City city = cities.get(position); if (citiesQeque.peek() == city){ citiesQeque.pop(); changeDirection(); position += (city.rule.weight + 1) * direction; city = cities.get(position); } if(city.rule != null){ if(city.rule != rulesQeque.peekLast()){ rulesQeque.add(city.rule); position += city.rule.weight * direction; changeDirection(); citiesQeque.push(city); } else{ rulesQeque.removeLast(); position += direction; } } else{ position += direction; } return city; } private void changeDirection() { direction *= -1; } @Override public boolean hasNext() { return position < cities.size(); } @Override public Iterator<City> iterator() { position = 0; return this; } } And here is a sample program: public static void main(String[] args) { ArrayList<City> list = new ArrayList<>(); for(int i = 0 ; i < 20; i++){ list.add(new City()); } CitiesList citiesList = new CitiesList(); citiesList.init(list); for (City city : citiesList) { System.out.print(city + " "); } System.out.println("\n******************"); citiesList.swap(4, 8); for (City city : citiesList) { System.out.print(city + " "); } System.out.println("\n******************"); citiesList.swap(2, 15); for (City city : citiesList) { System.out.print(city + " "); } } How do I handle reverse intersections?

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  • Move a sphere along the swipe?

    - by gameOne
    I am trying to get a sphere curl based on the swipe. I know this has been asked many times, but still it's yearning to be answered. I have managed to add force on the direction of the swipe and it works near perfect. I also have all the swipe positions stored in a list. Now I would like to know how can the curl be achieved. I believe the the curve in the swipe can be calculated by the Vector dot product If theta is 0, then there is no need to add the swipe. If it is not, then add the curl. Maybe this condition is redundant if I managed to find how to curl the sphere along the swipe position The code that adds the force to sphere based on the swipe direction is as below: using UnityEngine; using System.Collections; using System.Collections.Generic; public class SwipeControl : MonoBehaviour { //First establish some variables private Vector3 fp; //First finger position private Vector3 lp; //Last finger position private Vector3 ip; //some intermediate finger position private float dragDistance; //Distance needed for a swipe to register public float power; private Vector3 footballPos; private bool canShoot = true; private float factor = 40f; private List<Vector3> touchPositions = new List<Vector3>(); void Start(){ dragDistance = Screen.height*20/100; Physics.gravity = new Vector3(0, -20, 0); footballPos = transform.position; } // Update is called once per frame void Update() { //Examine the touch inputs foreach (Touch touch in Input.touches) { /*if (touch.phase == TouchPhase.Began) { fp = touch.position; lp = touch.position; }*/ if (touch.phase == TouchPhase.Moved) { touchPositions.Add(touch.position); } if (touch.phase == TouchPhase.Ended) { fp = touchPositions[0]; lp = touchPositions[touchPositions.Count-1]; ip = touchPositions[touchPositions.Count/2]; //First check if it's actually a drag if (Mathf.Abs(lp.x - fp.x) > dragDistance || Mathf.Abs(lp.y - fp.y) > dragDistance) { //It's a drag //Now check what direction the drag was //First check which axis if (Mathf.Abs(lp.x - fp.x) > Mathf.Abs(lp.y - fp.y)) { //If the horizontal movement is greater than the vertical movement... if ((lp.x>fp.x) && canShoot) //If the movement was to the right) { //Right move float x = (lp.x - fp.x) / Screen.height * factor; rigidbody.AddForce((new Vector3(x,10,16))*power); Debug.Log("right "+(lp.x-fp.x));//MOVE RIGHT CODE HERE canShoot = false; //rigidbody.AddForce((new Vector3((lp.x-fp.x)/30,10,16))*power); StartCoroutine(ReturnBall()); } else { //Left move float x = (lp.x - fp.x) / Screen.height * factor; rigidbody.AddForce((new Vector3(x,10,16))*power); Debug.Log("left "+(lp.x-fp.x));//MOVE LEFT CODE HERE canShoot = false; //rigidbody.AddForce(new Vector3((lp.x-fp.x)/30,10,16)*power); StartCoroutine(ReturnBall()); } } else { //the vertical movement is greater than the horizontal movement if (lp.y>fp.y) //If the movement was up { //Up move float y = (lp.y-fp.y)/Screen.height*factor; float x = (lp.x - fp.x) / Screen.height * factor; rigidbody.AddForce((new Vector3(x,y,16))*power); Debug.Log("up "+(lp.x-fp.x));//MOVE UP CODE HERE canShoot = false; //rigidbody.AddForce(new Vector3((lp.x-fp.x)/30,10,16)*power); StartCoroutine(ReturnBall()); } else { //Down move Debug.Log("down "+lp+" "+fp);//MOVE DOWN CODE HERE } } } else { //It's a tap Debug.Log("none");//TAP CODE HERE } } } } IEnumerator ReturnBall() { yield return new WaitForSeconds(5.0f); rigidbody.velocity = Vector3.zero; rigidbody.angularVelocity = Vector3.zero; transform.position = footballPos; canShoot =true; isKicked = false; } }

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  • Sorting Algorithms

    - by MarkPearl
    General Every time I go back to university I find myself wading through sorting algorithms and their implementation in C++. Up to now I haven’t really appreciated their true value. However as I discovered this last week with Dictionaries in C# – having a knowledge of some basic programming principles can greatly improve the performance of a system and make one think twice about how to tackle a problem. I’m going to cover briefly in this post the following: Selection Sort Insertion Sort Shellsort Quicksort Mergesort Heapsort (not complete) Selection Sort Array based selection sort is a simple approach to sorting an unsorted array. Simply put, it repeats two basic steps to achieve a sorted collection. It starts with a collection of data and repeatedly parses it, each time sorting out one element and reducing the size of the next iteration of parsed data by one. So the first iteration would go something like this… Go through the entire array of data and find the lowest value Place the value at the front of the array The second iteration would go something like this… Go through the array from position two (position one has already been sorted with the smallest value) and find the next lowest value in the array. Place the value at the second position in the array This process would be completed until the entire array had been sorted. A positive about selection sort is that it does not make many item movements. In fact, in a worst case scenario every items is only moved once. Selection sort is however a comparison intensive sort. If you had 10 items in a collection, just to parse the collection you would have 10+9+8+7+6+5+4+3+2=54 comparisons to sort regardless of how sorted the collection was to start with. If you think about it, if you applied selection sort to a collection already sorted, you would still perform relatively the same number of iterations as if it was not sorted at all. Many of the following algorithms try and reduce the number of comparisons if the list is already sorted – leaving one with a best case and worst case scenario for comparisons. Likewise different approaches have different levels of item movement. Depending on what is more expensive, one may give priority to one approach compared to another based on what is more expensive, a comparison or a item move. Insertion Sort Insertion sort tries to reduce the number of key comparisons it performs compared to selection sort by not “doing anything” if things are sorted. Assume you had an collection of numbers in the following order… 10 18 25 30 23 17 45 35 There are 8 elements in the list. If we were to start at the front of the list – 10 18 25 & 30 are already sorted. Element 5 (23) however is smaller than element 4 (30) and so needs to be repositioned. We do this by copying the value at element 5 to a temporary holder, and then begin shifting the elements before it up one. So… Element 5 would be copied to a temporary holder 10 18 25 30 23 17 45 35 – T 23 Element 4 would shift to Element 5 10 18 25 30 30 17 45 35 – T 23 Element 3 would shift to Element 4 10 18 25 25 30 17 45 35 – T 23 Element 2 (18) is smaller than the temporary holder so we put the temporary holder value into Element 3. 10 18 23 25 30 17 45 35 – T 23   We now have a sorted list up to element 6. And so we would repeat the same process by moving element 6 to a temporary value and then shifting everything up by one from element 2 to element 5. As you can see, one major setback for this technique is the shifting values up one – this is because up to now we have been considering the collection to be an array. If however the collection was a linked list, we would not need to shift values up, but merely remove the link from the unsorted value and “reinsert” it in a sorted position. Which would reduce the number of transactions performed on the collection. So.. Insertion sort seems to perform better than selection sort – however an implementation is slightly more complicated. This is typical with most sorting algorithms – generally, greater performance leads to greater complexity. Also, insertion sort performs better if a collection of data is already sorted. If for instance you were handed a sorted collection of size n, then only n number of comparisons would need to be performed to verify that it is sorted. It’s important to note that insertion sort (array based) performs a number item moves – every time an item is “out of place” several items before it get shifted up. Shellsort – Diminishing Increment Sort So up to now we have covered Selection Sort & Insertion Sort. Selection Sort makes many comparisons and insertion sort (with an array) has the potential of making many item movements. Shellsort is an approach that takes the normal insertion sort and tries to reduce the number of item movements. In Shellsort, elements in a collection are viewed as sub-collections of a particular size. Each sub-collection is sorted so that the elements that are far apart move closer to their final position. Suppose we had a collection of 15 elements… 10 20 15 45 36 48 7 60 18 50 2 19 43 30 55 First we may view the collection as 7 sub-collections and sort each sublist, lets say at intervals of 7 10 60 55 – 20 18 – 15 50 – 45 2 – 36 19 – 48 43 – 7 30 10 55 60 – 18 20 – 15 50 – 2 45 – 19 36 – 43 48 – 7 30 (Sorted) We then sort each sublist at a smaller inter – lets say 4 10 55 60 18 – 20 15 50 2 – 45 19 36 43 – 48 7 30 10 18 55 60 – 2 15 20 50 – 19 36 43 45 – 7 30 48 (Sorted) We then sort elements at a distance of 1 (i.e. we apply a normal insertion sort) 10 18 55 60 2 15 20 50 19 36 43 45 7 30 48 2 7 10 15 18 19 20 30 36 43 45 48 50 55 (Sorted) The important thing with shellsort is deciding on the increment sequence of each sub-collection. From what I can tell, there isn’t any definitive method and depending on the order of your elements, different increment sequences may perform better than others. There are however certain increment sequences that you may want to avoid. An even based increment sequence (e.g. 2 4 8 16 32 …) should typically be avoided because it does not allow for even elements to be compared with odd elements until the final sort phase – which in a way would negate many of the benefits of using sub-collections. The performance on the number of comparisons and item movements of Shellsort is hard to determine, however it is considered to be considerably better than the normal insertion sort. Quicksort Quicksort uses a divide and conquer approach to sort a collection of items. The collection is divided into two sub-collections – and the two sub-collections are sorted and combined into one list in such a way that the combined list is sorted. The algorithm is in general pseudo code below… Divide the collection into two sub-collections Quicksort the lower sub-collection Quicksort the upper sub-collection Combine the lower & upper sub-collection together As hinted at above, quicksort uses recursion in its implementation. The real trick with quicksort is to get the lower and upper sub-collections to be of equal size. The size of a sub-collection is determined by what value the pivot is. Once a pivot is determined, one would partition to sub-collections and then repeat the process on each sub collection until you reach the base case. With quicksort, the work is done when dividing the sub-collections into lower & upper collections. The actual combining of the lower & upper sub-collections at the end is relatively simple since every element in the lower sub-collection is smaller than the smallest element in the upper sub-collection. Mergesort With quicksort, the average-case complexity was O(nlog2n) however the worst case complexity was still O(N*N). Mergesort improves on quicksort by always having a complexity of O(nlog2n) regardless of the best or worst case. So how does it do this? Mergesort makes use of the divide and conquer approach to partition a collection into two sub-collections. It then sorts each sub-collection and combines the sorted sub-collections into one sorted collection. The general algorithm for mergesort is as follows… Divide the collection into two sub-collections Mergesort the first sub-collection Mergesort the second sub-collection Merge the first sub-collection and the second sub-collection As you can see.. it still pretty much looks like quicksort – so lets see where it differs… Firstly, mergesort differs from quicksort in how it partitions the sub-collections. Instead of having a pivot – merge sort partitions each sub-collection based on size so that the first and second sub-collection of relatively the same size. This dividing keeps getting repeated until the sub-collections are the size of a single element. If a sub-collection is one element in size – it is now sorted! So the trick is how do we put all these sub-collections together so that they maintain their sorted order. Sorted sub-collections are merged into a sorted collection by comparing the elements of the sub-collection and then adjusting the sorted collection. Lets have a look at a few examples… Assume 2 sub-collections with 1 element each 10 & 20 Compare the first element of the first sub-collection with the first element of the second sub-collection. Take the smallest of the two and place it as the first element in the sorted collection. In this scenario 10 is smaller than 20 so 10 is taken from sub-collection 1 leaving that sub-collection empty, which means by default the next smallest element is in sub-collection 2 (20). So the sorted collection would be 10 20 Lets assume 2 sub-collections with 2 elements each 10 20 & 15 19 So… again we would Compare 10 with 15 – 10 is the winner so we add it to our sorted collection (10) leaving us with 20 & 15 19 Compare 20 with 15 – 15 is the winner so we add it to our sorted collection (10 15) leaving us with 20 & 19 Compare 20 with 19 – 19 is the winner so we add it to our sorted collection (10 15 19) leaving us with 20 & _ 20 is by default the winner so our sorted collection is 10 15 19 20. Make sense? Heapsort (still needs to be completed) So by now I am tired of sorting algorithms and trying to remember why they were so important. I think every year I go through this stuff I wonder to myself why are we made to learn about selection sort and insertion sort if they are so bad – why didn’t we just skip to Mergesort & Quicksort. I guess the only explanation I have for this is that sometimes you learn things so that you can implement them in future – and other times you learn things so that you know it isn’t the best way of implementing things and that you don’t need to implement it in future. Anyhow… luckily this is going to be the last one of my sorts for today. The first step in heapsort is to convert a collection of data into a heap. After the data is converted into a heap, sorting begins… So what is the definition of a heap? If we have to convert a collection of data into a heap, how do we know when it is a heap and when it is not? The definition of a heap is as follows: A heap is a list in which each element contains a key, such that the key in the element at position k in the list is at least as large as the key in the element at position 2k +1 (if it exists) and 2k + 2 (if it exists). Does that make sense? At first glance I’m thinking what the heck??? But then after re-reading my notes I see that we are doing something different – up to now we have really looked at data as an array or sequential collection of data that we need to sort – a heap represents data in a slightly different way – although the data is stored in a sequential collection, for a sequential collection of data to be in a valid heap – it is “semi sorted”. Let me try and explain a bit further with an example… Example 1 of Potential Heap Data Assume we had a collection of numbers as follows 1[1] 2[2] 3[3] 4[4] 5[5] 6[6] For this to be a valid heap element with value of 1 at position [1] needs to be greater or equal to the element at position [3] (2k +1) and position [4] (2k +2). So in the above example, the collection of numbers is not in a valid heap. Example 2 of Potential Heap Data Lets look at another collection of numbers as follows 6[1] 5[2] 4[3] 3[4] 2[5] 1[6] Is this a valid heap? Well… element with the value 6 at position 1 must be greater or equal to the element at position [3] and position [4]. Is 6 > 4 and 6 > 3? Yes it is. Lets look at element 5 as position 2. It must be greater than the values at [4] & [5]. Is 5 > 3 and 5 > 2? Yes it is. If you continued to examine this second collection of data you would find that it is in a valid heap based on the definition of a heap.

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  • Making pascal's triangle with mpz_t's

    - by SDLFunTimes
    Hey, I'm trying to convert a function I wrote to generate an array of longs that respresents Pascal's triangles into a function that returns an array of mpz_t's. However with the following code: mpz_t* make_triangle(int rows, int* count) { //compute triangle size using 1 + 2 + 3 + ... n = n(n + 1) / 2 *count = (rows * (rows + 1)) / 2; mpz_t* triangle = malloc((*count) * sizeof(mpz_t)); //fill in first two rows mpz_t one; mpz_init(one); mpz_set_si(one, 1); triangle[0] = one; triangle[1] = one; triangle[2] = one; int nums_to_fill = 1; int position = 3; int last_row_pos; int r, i; for(r = 3; r <= rows; r++) { //left most side triangle[position] = one; position++; //inner numbers mpz_t new_num; mpz_init(new_num); last_row_pos = ((r - 1) * (r - 2)) / 2; for(i = 0; i < nums_to_fill; i++) { mpz_add(new_num, triangle[last_row_pos + i], triangle[last_row_pos + i + 1]); triangle[position] = new_num; mpz_clear(new_num); position++; } nums_to_fill++; //right most side triangle[position] = one; position++; } return triangle; } I'm getting errors saying: incompatible types in assignment for all lines where a position in the triangle is being set (i.e.: triangle[position] = one;). Does anyone know what I might be doing wrong?

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  • COCOS2D - Animation Stops During Move

    - by maiko
    Hey guys! I am trying to run a "Walk" style animation on my main game sprite. The animations work fine, and my sprite is hooked up to my joystick all fine and dandy. However, I think where I setup the call for my walk animations are wrong. Because everytime the sprite is moving, the animation stops. I know putting the animation in such a weak if statement is probably bad, but please tell me how I could get my sprite to animate properly while it is being moved by the joystick. The sprite faces the right direction, so I can tell the action's first frame is being called, however, it doesn't animate until I stop touching my joystick. Here is How I call the action: //WALK LEFT if (joypadCap.position.x <= 69 /*&& joypadCap.position.y < && joypadCap.position.y 40 */ ) { [tjSprite runAction:walkLeft]; }; //WALK RIGHT if ( joypadCap.position.x = 71 /* && joypadCap.position.y < 100 && joypadCap.position.y 40 */) { [tjSprite runAction:walkRight]; }; THIS: is the how the joystick controls the character: CGPoint newLocation = ccp(tjSprite.position.x - distance/8 * cosf(touchAngle), tjSprite.position.y - distance/8 * sinf(touchAngle)); tjSprite.position = newLocation; Please help. Any alternative ways to call the characters walk animation would be greatly appreciated!

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  • Positioning decorated series of div tags on screen using offset, DOM JQUERY RELATED

    - by Calibre2010
    Hi, I am using JQuery to position a series of div tags which basically use a class inside of the tag which decorates the divs as bars. So the div is a green box based on its css specifications to the glass. I have a list of STARTING postions, a list of left coordiantes- for the starting points I wish to position my DIV say 556, 560, 600 these automatically are generated as left positions in a list I have a list of ENDING postions, a list of left coordiantes- for the ending points I wish to position my DIV say 570, 590, 610 these automatically are generated as left positions in a list now for each start and end position, the bar(green box) i want to be drawn with its appropriate width as follows. so say f is the offset or position of the start and ff the offset or position of the end : Below draws the green box based on only one start and end position LEFT. if (f.left != 0) { $("#test").html($("<div>d</div>")).css({ position: 'absolute', left: (f.left) + "px", top: (f.top + 35) + "px", width: (ff.left - f.left) + 25 + "px" }).addClass("option1"); } I am looking to loop through the list of positons in the list and draw multiple green boxs based on the positions on the screen. The above code draws just one green box from the last offset position.

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  • strange segmentation fault during function return

    - by Kyle
    I am running a program on 2 different machines. On one it works fine without issue. On the other it results in a segmentation fault. Through debugging, I have figured out where the fault occurs, but I can't figure out a logical reason for it to happen. In one function I have the following code: pass_particles(particle_grid, particle_properties, input_data, coll_eros_track, collision_number_part, world, grid_rank_lookup, grid_locations); cout<<"done passing particles"<<endl; The function pass_particles looks like: void pass_particles(map<int,map<int,Particle> > & particle_grid, std::vector<Particle_props> & particle_properties, User_input& input_data, data_tracking & coll_eros_track, vector<int> & collision_number_part, mpi::communicator & world, std::map<int,int> & grid_rank_lookup, map<int,std::vector<double> > & grid_locations) { //cout<<"east-west"<<endl; //east-west exchange (x direction) map<int, vector<Particle> > particles_to_be_sent_east; map<int, vector<Particle> > particles_to_be_sent_west; vector<Particle> particles_received_east; vector<Particle> particles_received_west; int counter_x_sent=0; int counter_x_received=0; for(grid_iter=particle_grid.begin();grid_iter!=particle_grid.end();grid_iter++) { map<int,Particle>::iterator part_iter; for (part_iter=grid_iter->second.begin();part_iter!=grid_iter->second.end();) { if (particle_properties[part_iter->second.global_part_num()].particle_in_box()[grid_iter->first]) { //decide if a particle has left the box...need to consider whether particle was already outside the box if ((part_iter->second.position().x()<(grid_locations[grid_iter->first][0]) && part_iter->second.position().x()>(grid_locations[grid_iter->first-input_data.z_numboxes()][0])) || (input_data.periodic_walls_x() && (grid_iter->first-floor(grid_iter->first/(input_data.xz_numboxes()))*input_data.xz_numboxes()<input_data.z_numboxes()) && (part_iter->second.position().x()>(grid_locations[input_data.total_boxes()-1][0])))) { particles_to_be_sent_west[grid_iter->first].push_back(part_iter->second); particle_properties[particle_grid[grid_iter->first][part_iter->first].global_part_num()].particle_in_box()[grid_iter->first]=false; counter_sent++; counter_x_sent++; } else if ((part_iter->second.position().x()>(grid_locations[grid_iter->first][1]) && part_iter->second.position().x()<(grid_locations[grid_iter->first+input_data.z_numboxes()][1])) || (input_data.periodic_walls_x() && (grid_iter->first-floor(grid_iter->first/(input_data.xz_numboxes()))*input_data.xz_numboxes())>input_data.xz_numboxes()-input_data.z_numboxes()-1) && (part_iter->second.position().x()<(grid_locations[0][1]))) { particles_to_be_sent_east[grid_iter->first].push_back(part_iter->second); particle_properties[particle_grid[grid_iter->first][part_iter->first].global_part_num()].particle_in_box()[grid_iter->first]=false; counter_sent++; counter_x_sent++; } //select particles in overlap areas to send to neighboring cells else if ((part_iter->second.position().x()>(grid_locations[grid_iter->first][0]) && part_iter->second.position().x()<(grid_locations[grid_iter->first][0]+input_data.diam_large()))) { particles_to_be_sent_west[grid_iter->first].push_back(part_iter->second); counter_sent++; counter_x_sent++; } else if ((part_iter->second.position().x()<(grid_locations[grid_iter->first][1]) && part_iter->second.position().x()>(grid_locations[grid_iter->first][1]-input_data.diam_large()))) { particles_to_be_sent_east[grid_iter->first].push_back(part_iter->second); counter_sent++; counter_x_sent++; } ++part_iter; } else if (particles_received_current[grid_iter->first].find(part_iter->first)!=particles_received_current[grid_iter->first].end()) { if ((part_iter->second.position().x()>(grid_locations[grid_iter->first][0]) && part_iter->second.position().x()<(grid_locations[grid_iter->first][0]+input_data.diam_large()))) { particles_to_be_sent_west[grid_iter->first].push_back(part_iter->second); counter_sent++; counter_x_sent++; } else if ((part_iter->second.position().x()<(grid_locations[grid_iter->first][1]) && part_iter->second.position().x()>(grid_locations[grid_iter->first][1]-input_data.diam_large()))) { particles_to_be_sent_east[grid_iter->first].push_back(part_iter->second); counter_sent++; counter_x_sent++; } part_iter++; } else { particle_grid[grid_iter->first].erase(part_iter++); counter_removed++; } } } world.barrier(); mpi::request reqs_x_send[particles_to_be_sent_west.size()+particles_to_be_sent_east.size()]; vector<multimap<int,int> > box_sent_x_info; box_sent_x_info.resize(world.size()); vector<multimap<int,int> > box_received_x_info; box_received_x_info.resize(world.size()); int counter_x_reqs=0; //send particles for(grid_iter_vec=particles_to_be_sent_west.begin();grid_iter_vec!=particles_to_be_sent_west.end();grid_iter_vec++) { if (grid_iter_vec->second.size()!=0) { //send a particle. 50 will be "west" tag if (input_data.periodic_walls_x() && (grid_iter_vec->first-floor(grid_iter_vec->first/(input_data.xz_numboxes()))*input_data.xz_numboxes()<input_data.z_numboxes())) { reqs_x_send[counter_x_reqs++]=world.isend(grid_rank_lookup[grid_iter_vec->first + input_data.z_numboxes()*(input_data.x_numboxes()-1)], grid_iter_vec->first + input_data.z_numboxes()*(input_data.x_numboxes()-1), particles_to_be_sent_west[grid_iter_vec->first]); box_sent_x_info[grid_rank_lookup[grid_iter_vec->first + input_data.z_numboxes()*(input_data.x_numboxes()-1)]].insert(pair<int,int>(world.rank(), grid_iter_vec->first + input_data.z_numboxes()*(input_data.x_numboxes()-1))); } else if (!(grid_iter_vec->first-floor(grid_iter_vec->first/(input_data.xz_numboxes()))*input_data.xz_numboxes()<input_data.z_numboxes())) { reqs_x_send[counter_x_reqs++]=world.isend(grid_rank_lookup[grid_iter_vec->first - input_data.z_numboxes()], grid_iter_vec->first - input_data.z_numboxes(), particles_to_be_sent_west[grid_iter_vec->first]); box_sent_x_info[grid_rank_lookup[grid_iter_vec->first - input_data.z_numboxes()]].insert(pair<int,int>(world.rank(),grid_iter_vec->first - input_data.z_numboxes())); } } } for(grid_iter_vec=particles_to_be_sent_east.begin();grid_iter_vec!=particles_to_be_sent_east.end();grid_iter_vec++) { if (grid_iter_vec->second.size()!=0) { //send a particle. 60 will be "east" tag if (input_data.periodic_walls_x() && (grid_iter_vec->first-floor(grid_iter_vec->first/(input_data.xz_numboxes())*input_data.xz_numboxes())>input_data.xz_numboxes()-input_data.z_numboxes()-1)) { reqs_x_send[counter_x_reqs++]=world.isend(grid_rank_lookup[grid_iter_vec->first - input_data.z_numboxes()*(input_data.x_numboxes()-1)], 2000000000-(grid_iter_vec->first - input_data.z_numboxes()*(input_data.x_numboxes()-1)), particles_to_be_sent_east[grid_iter_vec->first]); box_sent_x_info[grid_rank_lookup[grid_iter_vec->first - input_data.z_numboxes()*(input_data.x_numboxes()-1)]].insert(pair<int,int>(world.rank(),2000000000-(grid_iter_vec->first - input_data.z_numboxes()*(input_data.x_numboxes()-1)))); } else if (!(grid_iter_vec->first-floor(grid_iter_vec->first/(input_data.xz_numboxes())*input_data.xz_numboxes())>input_data.xz_numboxes()-input_data.z_numboxes()-1)) { reqs_x_send[counter_x_reqs++]=world.isend(grid_rank_lookup[grid_iter_vec->first + input_data.z_numboxes()], 2000000000-(grid_iter_vec->first + input_data.z_numboxes()), particles_to_be_sent_east[grid_iter_vec->first]); box_sent_x_info[grid_rank_lookup[grid_iter_vec->first + input_data.z_numboxes()]].insert(pair<int,int>(world.rank(), 2000000000-(grid_iter_vec->first + input_data.z_numboxes()))); } } } counter=0; for (int i=0;i<world.size();i++) { //if (world.rank()!=i) //{ reqs[counter++]=world.isend(i,1000000000,box_sent_x_info[i]); reqs[counter++]=world.irecv(i,1000000000,box_received_x_info[i]); //} } mpi::wait_all(reqs, reqs + world.size()*2); //receive particles //receive west particles for (int j=0;j<world.size();j++) { multimap<int,int>::iterator received_info_iter; for (received_info_iter=box_received_x_info[j].begin();received_info_iter!=box_received_x_info[j].end();received_info_iter++) { //receive the message if (received_info_iter->second<1000000000) { //receive the message world.recv(received_info_iter->first,received_info_iter->second,particles_received_west); //loop through all the received particles and add them to the particle_grid for this processor for (unsigned int i=0;i<particles_received_west.size();i++) { particle_grid[received_info_iter->second].insert(pair<int,Particle>(particles_received_west[i].global_part_num(),particles_received_west[i])); if(particles_received_west[i].position().x()>grid_locations[received_info_iter->second][0] && particles_received_west[i].position().x()<grid_locations[received_info_iter->second][1]) { particle_properties[particles_received_west[i].global_part_num()].particle_in_box()[received_info_iter->second]=true; } counter_received++; counter_x_received++; } } else { //receive the message world.recv(received_info_iter->first,received_info_iter->second,particles_received_east); //loop through all the received particles and add them to the particle_grid for this processor for (unsigned int i=0;i<particles_received_east.size();i++) { particle_grid[2000000000-received_info_iter->second].insert(pair<int,Particle>(particles_received_east[i].global_part_num(),particles_received_east[i])); if(particles_received_east[i].position().x()>grid_locations[2000000000-received_info_iter->second][0] && particles_received_east[i].position().x()<grid_locations[2000000000-received_info_iter->second][1]) { particle_properties[particles_received_east[i].global_part_num()].particle_in_box()[2000000000-received_info_iter->second]=true; } counter_received++; counter_x_received++; } } } } mpi::wait_all(reqs_y_send, reqs_y_send + particles_to_be_sent_bottom.size()+particles_to_be_sent_top.size()); mpi::wait_all(reqs_z_send, reqs_z_send + particles_to_be_sent_south.size()+particles_to_be_sent_north.size()); mpi::wait_all(reqs_x_send, reqs_x_send + particles_to_be_sent_west.size()+particles_to_be_sent_east.size()); cout<<"x sent "<<counter_x_sent<<" and received "<<counter_x_received<<" from rank "<<world.rank()<<endl; cout<<"rank "<<world.rank()<<" sent "<<counter_sent<<" and received "<<counter_received<<" and removed "<<counter_removed<<endl; cout<<"done passing"<<endl; } I only posted some of the code (so ignore the fact that some variables may appear to be undefined, as they are in a portion of the code I didn't post) When I run the code (on the machine in which it fails), I get done passing but not done passing particles I am lost as to what could possibly cause a segmentation fault between the end of the called function and the next line in the calling function and why it would happen on one machine and not another.

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  • 2d movement solution

    - by Phil
    Hi! I'm making a simple top-down tank game on the ipad where the user controls the movement of the tank with the left "joystick" and the rotation of the turret with the right one. I've spent several hours just trying to get it to work decently but now I turn to the pros :) I have two referencial objects, one for the movement and one for the rotation. The referencial objects always stay max two units away from the tank and I use them to tell the tank in what direction to move. I chose this approach to decouple movement and rotational behaviour from the raw input of the joysticks, I believe this will make it simpler to implement whatever behaviour I want for the tank. My problem is 1; the turret rotates the long way to the target. With this I mean that the target can be -5 degrees away in rotation and still it rotates 355 degrees instead of -5 degrees. I can't figure out why. The other problem is with the movement. It just doesn't feel right to have the tank turn while moving. I'd like to have a solution that would work as well for the AI as for the player. A blackbox function for the movement where the player only specifies in what direction it should move and it moves there under the constraints that are imposed on it. I am using the standard joystick class found in the Unity iPhone package. This is the code I'm using for the movement: public class TankFollow : MonoBehaviour { //Check angle difference and turn accordingly public GameObject followPoint; public float speed; public float turningSpeed; void Update() { transform.position = Vector3.Slerp(transform.position, followPoint.transform.position, speed * Time.deltaTime); //Calculate angle var forwardA = transform.forward; var forwardB = (followPoint.transform.position - transform.position); var angleA = Mathf.Atan2(forwardA.x, forwardA.z) * Mathf.Rad2Deg; var angleB = Mathf.Atan2(forwardB.x, forwardB.z) * Mathf.Rad2Deg; var angleDiff = Mathf.DeltaAngle(angleA, angleB); //print(angleDiff.ToString()); if (angleDiff > 5) { //Rotate to transform.Rotate(new Vector3(0, (-turningSpeed * Time.deltaTime),0)); //transform.rotation = new Quaternion(transform.rotation.x, transform.rotation.y + adjustment, transform.rotation.z, transform.rotation.w); } else if (angleDiff < 5) { transform.Rotate(new Vector3(0, (turningSpeed * Time.deltaTime),0)); //transform.rotation = new Quaternion(transform.rotation.x, transform.rotation.y + adjustment, transform.rotation.z, transform.rotation.w); } else { } transform.position = new Vector3(transform.position.x, 0, transform.position.z); } } And this is the code I'm using to rotate the turret: void LookAt() { var forwardA = -transform.right; var forwardB = (toLookAt.transform.position - transform.position); var angleA = Mathf.Atan2(forwardA.x, forwardA.z) * Mathf.Rad2Deg; var angleB = Mathf.Atan2(forwardB.x, forwardB.z) * Mathf.Rad2Deg; var angleDiff = Mathf.DeltaAngle(angleA, angleB); //print(angleDiff.ToString()); if (angleDiff - 180 > 1) { //Rotate to transform.Rotate(new Vector3(0, (turretSpeed * Time.deltaTime),0)); //transform.rotation = new Quaternion(transform.rotation.x, transform.rotation.y + adjustment, transform.rotation.z, transform.rotation.w); } else if (angleDiff - 180 < -1) { transform.Rotate(new Vector3(0, (-turretSpeed * Time.deltaTime),0)); //transform.rotation = new Quaternion(transform.rotation.x, transform.rotation.y + adjustment, transform.rotation.z, transform.rotation.w); print((angleDiff - 180).ToString()); } else { } } Since I want the turret reference point to turn in relation to the tank (when you rotate the body, the turret should follow and not stay locked on since it makes it impossible to control when you've got two thumbs to work with), I've made the TurretFollowPoint a child of the Turret object, which in turn is a child of the body. I'm thinking that I'm making it too difficult for myself with the reference points but I'm imagining that it's a good idea. Please be honest about this point. So I'll be grateful for any help I can get! I'm using Unity3d iPhone. Thanks!

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  • 2d tank movement and turret solution

    - by Phil
    Hi! I'm making a simple top-down tank game on the ipad where the user controls the movement of the tank with the left "joystick" and the rotation of the turret with the right one. I've spent several hours just trying to get it to work decently but now I turn to the pros :) I have two referencial objects, one for the movement and one for the rotation. The referencial objects always stay max two units away from the tank and I use them to tell the tank in what direction to move. I chose this approach to decouple movement and rotational behaviour from the raw input of the joysticks, I believe this will make it simpler to implement whatever behaviour I want for the tank. My problem is 1; the turret rotates the long way to the target. With this I mean that the target can be -5 degrees away in rotation and still it rotates 355 degrees instead of -5 degrees. I can't figure out why. The other problem is with the movement. It just doesn't feel right to have the tank turn while moving. I'd like to have a solution that would work as well for the AI as for the player. A blackbox function for the movement where the player only specifies in what direction it should move and it moves there under the constraints that are imposed on it. I am using the standard joystick class found in the Unity iPhone package. This is the code I'm using for the movement: public class TankFollow : MonoBehaviour { //Check angle difference and turn accordingly public GameObject followPoint; public float speed; public float turningSpeed; void Update() { transform.position = Vector3.Slerp(transform.position, followPoint.transform.position, speed * Time.deltaTime); //Calculate angle var forwardA = transform.forward; var forwardB = (followPoint.transform.position - transform.position); var angleA = Mathf.Atan2(forwardA.x, forwardA.z) * Mathf.Rad2Deg; var angleB = Mathf.Atan2(forwardB.x, forwardB.z) * Mathf.Rad2Deg; var angleDiff = Mathf.DeltaAngle(angleA, angleB); //print(angleDiff.ToString()); if (angleDiff > 5) { //Rotate to transform.Rotate(new Vector3(0, (-turningSpeed * Time.deltaTime),0)); //transform.rotation = new Quaternion(transform.rotation.x, transform.rotation.y + adjustment, transform.rotation.z, transform.rotation.w); } else if (angleDiff < 5) { transform.Rotate(new Vector3(0, (turningSpeed * Time.deltaTime),0)); //transform.rotation = new Quaternion(transform.rotation.x, transform.rotation.y + adjustment, transform.rotation.z, transform.rotation.w); } else { } transform.position = new Vector3(transform.position.x, 0, transform.position.z); } } And this is the code I'm using to rotate the turret: void LookAt() { var forwardA = -transform.right; var forwardB = (toLookAt.transform.position - transform.position); var angleA = Mathf.Atan2(forwardA.x, forwardA.z) * Mathf.Rad2Deg; var angleB = Mathf.Atan2(forwardB.x, forwardB.z) * Mathf.Rad2Deg; var angleDiff = Mathf.DeltaAngle(angleA, angleB); //print(angleDiff.ToString()); if (angleDiff - 180 > 1) { //Rotate to transform.Rotate(new Vector3(0, (turretSpeed * Time.deltaTime),0)); //transform.rotation = new Quaternion(transform.rotation.x, transform.rotation.y + adjustment, transform.rotation.z, transform.rotation.w); } else if (angleDiff - 180 < -1) { transform.Rotate(new Vector3(0, (-turretSpeed * Time.deltaTime),0)); //transform.rotation = new Quaternion(transform.rotation.x, transform.rotation.y + adjustment, transform.rotation.z, transform.rotation.w); print((angleDiff - 180).ToString()); } else { } } Since I want the turret reference point to turn in relation to the tank (when you rotate the body, the turret should follow and not stay locked on since it makes it impossible to control when you've got two thumbs to work with), I've made the TurretFollowPoint a child of the Turret object, which in turn is a child of the body. I'm thinking that I'm making it too difficult for myself with the reference points but I'm imagining that it's a good idea. Please be honest about this point. So I'll be grateful for any help I can get! I'm using Unity3d iPhone. Thanks!

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  • 2D tower defense - A bullet to an enemy

    - by Tashu
    I'm trying to find a good solution for a bullet to hit the enemy. The game is 2D tower defense, the tower is supposed to shoot a bullet and hit the enemy guaranteed. I tried this solution - http://blog.wolfire.com/2009/07/linear-algebra-for-game-developers-part-1/ The link mentioned to subtract the bullet's origin and the enemy as well (vector subtraction). I tried that but a bullet just follows around the enemy. float diffX = enemy.position.x - position.x; float diffY = enemy.position.y - position.y; velocity.x = diffX; velocity.y = diffY; position.add(velocity.x * deltaTime, velocity.y * deltaTime); I'm familiar with vectors but not sure what steps (vector math operations) to be done to get this solution working.

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  • Smooth Camera Rotation around 90 degrees

    - by Nicholas
    I'm developing a third person 3D platformer in XNA. My problem is when I try to rotate the camera around the player. I would like to rotate (and animate) the camera 90 degrees around the player. So the camera should rotate until it has reached 90 degrees from the starting position. I cannot figure out how to keep track of the rotation, and when the rotation has made the full 90 degrees. Currently my cameras update: public void Update(Vector3 playerPosition) { if (rotateCamera) { position = Vector3.Transform(position - playerPosition, Matrix.CreateRotationY(0.1f)) + playerPosition; } this.viewMatrix = Matrix.CreateLookAt(position, playerPosition, Vector3.Up); } The initial position of the camera is set in the constructor. The "rotateCamera" bool is set on keypress. Thanks for the help in advance. Cheers.

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  • Triangle Picking Picking Back faces

    - by Tangeleno
    I'm having a bit of trouble with 3D picking, at first I thought my ray was inaccurate but it turns out that the picking is happening on faces facing the camera and faces facing away from the camera which I'm currently culling. Here's my ray creation code, I'm pretty sure the problem isn't here but I've been wrong before. private uint Pick() { Ray cursorRay = CalculateCursorRay(); Vector3? point = Control.Mesh.RayCast(cursorRay); if (point != null) { Tile hitTile = Control.TileMesh.GetTileAtPoint(point); return hitTile == null ? uint.MaxValue : (uint)(hitTile.X + hitTile.Y * Control.Generator.TilesWide); } return uint.MaxValue; } private Ray CalculateCursorRay() { Vector3 nearPoint = Control.Camera.Unproject(new Vector3(Cursor.Position.X, Control.ClientRectangle.Height - Cursor.Position.Y, 0f)); Vector3 farPoint = Control.Camera.Unproject(new Vector3(Cursor.Position.X, Control.ClientRectangle.Height - Cursor.Position.Y, 1f)); Vector3 direction = farPoint - nearPoint; direction.Normalize(); return new Ray(nearPoint, direction); } public Vector3 Camera.Unproject(Vector3 source) { Vector4 result; result.X = (source.X - _control.ClientRectangle.X) * 2 / _control.ClientRectangle.Width - 1; result.Y = (source.Y - _control.ClientRectangle.Y) * 2 / _control.ClientRectangle.Height - 1; result.Z = source.Z - 1; if (_farPlane - 1 == 0) result.Z = 0; else result.Z = result.Z / (_farPlane - 1); result.W = 1f; result = Vector4.Transform(result, Matrix4.Invert(ProjectionMatrix)); result = Vector4.Transform(result, Matrix4.Invert(ViewMatrix)); result = Vector4.Transform(result, Matrix4.Invert(_world)); result = Vector4.Divide(result, result.W); return new Vector3(result.X, result.Y, result.Z); } And my triangle intersection code. Ripped mainly from the XNA picking sample. public float? Intersects(Ray ray) { float? closestHit = Bounds.Intersects(ray); if (closestHit != null && Vertices.Length == 3) { Vector3 e1, e2; Vector3.Subtract(ref Vertices[1].Position, ref Vertices[0].Position, out e1); Vector3.Subtract(ref Vertices[2].Position, ref Vertices[0].Position, out e2); Vector3 directionCrossEdge2; Vector3.Cross(ref ray.Direction, ref e2, out directionCrossEdge2); float determinant; Vector3.Dot(ref e1, ref directionCrossEdge2, out determinant); if (determinant > -float.Epsilon && determinant < float.Epsilon) return null; float inverseDeterminant = 1.0f/determinant; Vector3 distanceVector; Vector3.Subtract(ref ray.Position, ref Vertices[0].Position, out distanceVector); float triangleU; Vector3.Dot(ref distanceVector, ref directionCrossEdge2, out triangleU); triangleU *= inverseDeterminant; if (triangleU < 0 || triangleU > 1) return null; Vector3 distanceCrossEdge1; Vector3.Cross(ref distanceVector, ref e1, out distanceCrossEdge1); float triangleV; Vector3.Dot(ref ray.Direction, ref distanceCrossEdge1, out triangleV); triangleV *= inverseDeterminant; if (triangleV < 0 || triangleU + triangleV > 1) return null; float rayDistance; Vector3.Dot(ref e2, ref distanceCrossEdge1, out rayDistance); rayDistance *= inverseDeterminant; if (rayDistance < 0) return null; return rayDistance; } return closestHit; } I'll admit I don't fully understand all of the math behind the intersection and that is something I'm working on, but my understanding was that if rayDistance was less than 0 the face was facing away from the camera, and shouldn't be counted as a hit. So my question is, is there an issue with my intersection or ray creation code, or is there another check I need to perform to tell if the face is facing away from the camera, and if so any hints on what that check might contain would be appreciated.

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  • How can I fix latency problems for car game?

    - by Freddy
    Basically I'm trying to make a online car racing game for IOS using Game Center real time multiplayer. I have setup a timer that sends data every 0.02 seconds to the other player with the current position and current angle. However sometimes, it will take LONGER then these 0.02 seconds for the package to be sent and then received. In this case i have implemented a method that "calculate" what the next position should be if no position is received based on the last position and angle. However, when the data then receives for let say 0.04 seconds after, it will change back to the last position, which will result in the car "jumping" back and lag. And If i just keep ignoring the data it will never take any input from the other user. Is their any way to prevent this? I suppose this needs to be fixed with some client-sided algorithm.

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  • movement of sprites with kinect and xna

    - by pablopp83
    im working on a proyect with kinect sdk and xna 4.0. i need take the position of the hands and draw a sprite over it. im doing it directly and, because of that, i get a "trembling hands" effect. so, i was thinking on make the sprite move from the previous position to the new one, given in every frame by the new hand position. this way, the sprite does not jump from one position to another. this is working just fine, but im using a constant value for the velocity, and i really would like to use a variable velocity given by the difference between the prev and the new position. this is, if the hand move more quickly in the reality, the velocity will be higher. I really dont have a clue on how to make this works. can somebody point me in the right direction? thanks.

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  • Saving more corsor positions (with tput?) in bash terminal

    - by AndreasT
    I know that tput sc saves the current cursor position and tput rc restores it exactly where tput sc was called. The problem is that every time tput sc is called, it overwrites the previous saved position. Is there a way to save more positions, e.g. tput sc pos1 and tput sc pos2 which can be restored with, say, tput rc pos1 and tput rc pos2 respectively? (The solution need not make use of tput, I mentioned it because it's the only command I know that handles cursor position) If not, is there a way to at least save the cursor position locally in a function, so that if a function uses tput sc and then calls another function that runs again tput sc, then each function restores its own saved cursor position when invoking tput rc? Thanks in advance.

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  • How to remove items from an arraylist without shrinking the list [migrated]

    - by user73710
    I have a case where I am using the ArrayList to keep a list of items that are keyed by their position in the list. Other objects reference the ArrayList items by their position. If I delete one of the items from the list, I don't want the list to shrink because that would invalidate all other references to items in the list (e.g. item 2 is now in position 1). My solution to the shrinking array list problem is to null the position in the arraylist so that the list will not shrink. I am curious whether this will free the memory formerly held by the item at that position. If there is a better way to accomplish this requirement, I would like to know about it.

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  • IE: position two text lines on top and bottom corners in table cell?

    - by diggonce
    I have a table with dynamic data. And there is a specific line of text which should be displayed only when a user hovers over the table row. This line of text should be 'fixed' to the table cell's bottom edge. It works so far with Firefox, but fails in IE. Live code can be seen here: http://2010resolutions.org/test/index.html The text in red should be fixed to the table cell's bottom border. (They will have a fixed height and width) Any clues how to get this working in IE? Any help is appreciated. Here's the code: <style> table { width: 500px; background: gray; } td { vertical-align: top; } .wrapper { position: relative; background: green; } tr, td, .wrapper { height: 100%; padding-bottom: 0.75em; } .bottom { position: absolute; left: 0; bottom: 0; background: red; } .bottom { visibility: hidden; } tr:hover .bottom { visibility: visible; } </style> <table> <tr class="data"> <td> <div class="wrapper"> This is line 1<br /> This is line 2<br /> This is line 3<br /> <span class="bottom">Bottom line 1</span> </div> </td> <td> <div class="wrapper"> This is line 4<br /> This is line 5<br /> This is line 6<br /> <span class="bottom">Bottom line 2</span></span> </div> </td> <td> <div class="wrapper"> This is line 7<br /> This is line 8<br /> This is line 9<br /> This is line 10<br /> This is line 11<br /> This is line 12<br /> <span class="bottom">Bottom line 3</span> </div> </td> </tr> <tr> <td>&nbsp;</td> <td>&nbsp;</td> <td>&nbsp;</td> </tr> </table>

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  • iOS: AVQueuePlayer/AVPlayerItem 'An AVPlayerItem can occupy only one position in a player's queue at a time.'

    - by JoshDG
    I keep getting this error: 'An AVPlayerItem can occupy only one position in a player's queue at a time.' I NSLog'd the players items, and none of them seem to be equal. Further, I added this just to be sure: if([player canInsertItem:itemToAdd afterItem:nil]) [player insertItem:itemToAdd afterItem:nil]; When I wasn't sure if that would work (can have two identical items in different memory locations) I wrote a category method to test if a player contains an item or something identical to it. Yet, I'm still getting the error. I've seen several posts of people getting this error with MPMoviePlayerController, but I'm not using that custom class, just the out of the box AVQueuePlayer. Any ideas on how to fix this?

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  • Positioning divs inside a container div without the content of an upper div affecting the position o

    - by silverCORE
    Hi. I'm trying to accomplish the following layout, and I'm almost there, except for the last green div, which is going lower and lower depending on the content of the content (white) div. If I set a value for the TOP property for the green div, and then I add some more text to the content div, the green div goes lower and lower. Since the green div is child to the main container div, and the green div is relatively positioned, isn't it supposed to be placed specifically at the position indicated by the TOP value of it? If I'm incorrect...can someone please tell me how can i make it so that the green div is always displayed at the same spot within the container (gray) div, regardless of the height of the content/white div? I tried to paste the css code here but was having problems with the brower. you can see the test site source/css at http://www.rae-mx.com/test tia for the help.

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  • Using LINQ to XML, how can I join two sets of data based on ordinal position?

    - by Donald Hughes
    Using LINQ to XML, how can I join two sets of data based on ordinal position? <document> <set1> <value>A</value> <value>B</value> <value>C</value> </set1> <set2> <value>1</value> <value>2</value> <value>3</value> </set2> </document> Based on the above fragment, I would like to join the two sets together such that "A" and "1" are in the same record, "B" and "2" are in the same record, and "C" and "3" are in the same record.

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  • C# Reading and Writing a Char[] to and from a Byte[] - Updated with Solution

    - by Simon G
    Hi, I have a byte array of around 10,000 bytes which is basically a blob from delphi that contains char, string, double and arrays of various types. This need to be read in and updated via C#. I've created a very basic reader that gets the byte array from the db and converts the bytes to the relevant object type when accessing the property which works fine. My problem is when I try to write to a specific char[] item, it doesn't seem to update the byte array. I've created the following extensions for reading and writing: public static class CharExtension { public static byte ToByte( this char c ) { return Convert.ToByte( c ); } public static byte ToByte( this char c, int position, byte[] blob ) { byte b = c.ToByte(); blob[position] = b; return b; } } public static class CharArrayExtension { public static byte[] ToByteArray( this char[] c ) { byte[] b = new byte[c.Length]; for ( int i = 1; i < c.Length; i++ ) { b[i] = c[i].ToByte(); } return b; } public static byte[] ToByteArray( this char[] c, int positon, int length, byte[] blob ) { byte[] b = c.ToByteArray(); Array.Copy( b, 0, blob, positon, length ); return b; } } public static class ByteExtension { public static char ToChar( this byte[] b, int position ) { return Convert.ToChar( b[position] ); } } public static class ByteArrayExtension { public static char[] ToCharArray( this byte[] b, int position, int length ) { char[] c = new char[length]; for ( int i = 0; i < length; i++ ) { c[i] = b.ToChar( position ); position += 1; } return c; } } to read and write chars and char arrays my code looks like: Byte[] _Blob; // set from a db field public char ubin { get { return _tariffBlob.ToChar( 14 ); } set { value.ToByte( 14, _Blob ); } } public char[] usercaplas { get { return _tariffBlob.ToCharArray( 2035, 10 ); } set { value.ToByteArray( 2035, 10, _Blob ); } } So to write to the objects I can do: ubin = 'C'; // this will update the byte[] usercaplas = new char[10] { 'A', 'B', etc. }; // this will update the byte[] usercaplas[3] = 'C'; // this does not update the byte[] I know the reason is that the setter property is not being called but I want to know is there a way around this using code similar to what I already have? I know a possible solution is to use a private variable called _usercaplas that I set and update as needed however as the byte array is nearly 10,000 bytes in length the class is already long and I would like a simpler approach as to reduce the overall code length and complexity. Thank Solution Here's my solution should anyone want it. If you have a better way of doing then let me know please. First I created a new class for the array: public class CharArrayList : ArrayList { char[] arr; private byte[] blob; private int length = 0; private int position = 0; public CharArrayList( byte[] blob, int position, int length ) { this.blob = blob; this.length = length; this.position = position; PopulateInternalArray(); SetArray(); } private void PopulateInternalArray() { arr = blob.ToCharArray( position, length ); } private void SetArray() { foreach ( char c in arr ) { this.Add( c ); } } private void UpdateInternalArray() { this.Clear(); SetArray(); } public char this[int i] { get { return arr[i]; } set { arr[i] = value; UpdateInternalArray(); } } } Then I created a couple of extension methods to help with converting to a byte[] public static byte[] ToByteArray( this CharArrayList c ) { byte[] b = new byte[c.Count]; for ( int i = 0; i < c.Count; i++ ) { b[i] = Convert.ToChar( c[i] ).ToByte(); } return b; } public static byte[] ToByteArray( this CharArrayList c, byte[] blob, int position, int length ) { byte[] b = c.ToByteArray(); Array.Copy( b, 0, blob, position, length ); return b; } So to read and write to the object: private CharArrayList _usercaplass; public CharArrayList usercaplas { get { if ( _usercaplass == null ) _usercaplass = new CharArrayList( _tariffBlob, 2035, 100 ); return _usercaplass; } set { _usercaplass = value; _usercaplass.ToByteArray( _tariffBlob, 2035, 100 ); } } As mentioned before its not an ideal solutions as I have to have private variables and extra code in the setter but I couldnt see a way around it.

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  • posmax: like argmax but gives the position(s) of the element x for which f[x] is maximal

    - by dreeves
    Mathematica has a built-in function ArgMax for functions over infinite domains, based on the standard mathematical definition. The analog for finite domains is a handy utility function. Given a function and a list (call it the domain of the function), return the element(s) of the list that maximize the function. Here's an example of finite argmax in action: http://stackoverflow.com/questions/471029/canonicalize-nfl-team-names/472213#472213 And here's my implementation of it (along with argmin for good measure): (* argmax[f, domain] returns the element of domain for which f of that element is maximal -- breaks ties in favor of first occurrence. *) SetAttributes[{argmax, argmin}, HoldFirst]; argmax[f_, dom_List] := Fold[If[f[#1]>=f[#2], #1, #2]&, First[dom], Rest[dom]] argmin[f_, dom_List] := argmax[-f[#]&, dom] First, is that the most efficient way to implement argmax? What if you want the list of all maximal elements instead of just the first one? Second, how about the related function posmax that, instead of returning the maximal element(s), returns the position(s) of the maximal elements?

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  • How can I re-size and re-position a shadowbox/greybox window to display in a certain div element?

    - by kielie
    Hi guys, I would like to know if it is possible to re-size and re-position a greybox or shadowbox window to display in a certain div element? I am creating a template for a wordpress site, and I am using the default calendar, but when you click on a date inside of the calendar, the default action is to open it up in a new window. Would it be possible to mod greybox or shadowbox in such a way that when you click on a date, the box opens up over the calendar displaying the contents in it, instead of a new page? Or is there another way of achieving the desired result, maybe with jQuery or Javascript? Any help would be greatly appreciated, thanx in advance!

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