I have a representation of a process trough something that is very much like a DAG (Directed Acyclic Graph). This graph is represented with an adjacency table, but not like a "regular" adjacency table, there are few differences:
Each entry in the table is a list of lists,
Each "inner" list states the predecessor nodes required.
The idea for this data structure is to hold requirements of steps within a process. So, for example:
P = {1:[[]], 2:[[1]], 3:[[2]], 4:[[3]], 5:[[2]], 6:[[]], 7: [[4,6],[8,5]], 8:[[]]}
For process P, step 1 doesn't require any predecessor, step requires step 1,..., step 6 also doesn't require any predecessor, step 7 requires steps (4 and 6) OR (8 and 5).
Each step has a state (some ID reference) that determines if the next step can be executed or not, or if the process can be terminated or not.
In the example above, I would not be able to execute step 2 if step 1 didn't fulfill some specific condition regarding the state the same for step 5, which requires step 2 with state=something specific. And for step 7, the only way to execute it, would be if step 4&6 OR 5&8 have their corresponding state=something specific.
What I need is a way to get all the unique paths that lead to a certain step, so later I can check against this paths if the conditions are met. For step 7 it would be :
paths = [[1,2,3,4,6],[1,2,5,8]]
I've checked:
Python get all paths from graph
How to implement the search for all paths inside a directed graph in JavaScript? (reversing this??)
Depth first search list paths to all end nodes
How to find the nodes that leads to node A without traversing all the graph (directed graph)
Most of the information around points to some sort of modified DFS or some kind of enhanced Dijkstra. For what I've checked and tested none of the above gives me what I need which is a list of all "unique paths" that lead to a node that may be reached from "different paths".
The question is not language specific, so any example in any language would be appreciated :)
EDIT: 04/01/22
Further clarifications:
The steps are one way, meaning that node 1 is connected to step 2 by a distance of 1, to step 3 a distance of 2, and so on. But step/node 1 is not conntected with 6 or 8.
All graphs have a unique starting point and ending point. In the example 1 and 7.
Yes, node 5 should be connected to node 7. Img updated.
The number of nodes will always be <100.
How big is your graph? What is your performance requirement?
For a small graph like your example, Dijsktra is almost instant. So you do not need to store all the paths.
Set cost of all links to 1
Set cost of links that lead to nodes that are NOT in the required state to 10^10
Run Dijkstra to find shortest path from source to destination through nodes in required state.
I think I've managed to get what I needed, nevertheless I think the answer is overly complex.
Function to populate a tracker object with all the possible paths.
const tracker = {};
function getPaths (step, branchRef) {
const currentStepRequires = getStepRequires(step); // func that gets the array of arrays of current step
const oldBranchRef = branchRef;
const hasBranches = currentStepRequires.length > 1;
for (const branch of currentStepRequires) {
if (branch.length === 0) {
return;
}
if (!hasBranches && !branchRef) {
tracker[branch] = [];
}
if (!branchRef) branchRef = branch;
if (hasBranches) {
if (oldBranchRef && oldBranchRef !== branchRef) {
tracker[branch] = [...tracker[oldBranchRef]];
}
else if (tracker[branchRef]) {
tracker[branch] = [...tracker[branchRef]];
branchRef = branch;
}
else {
tracker[branch] = [];
}
}
for (const step of branch) {
tracker[branchRef].push(step);
getPaths(step, branchRef);
}
if (hasBranches) branchRef = '';
}
}
After the tracker object has been populated I need to remove the paths that are contained within the other paths.
I'm using lodash here to simplify the filtering, checking and adding the paths
const paths = [];
_.forEach(_.sortBy(tracker, path => path.length * -1), branch => {
const isSubpath = _.some(paths, path => _.isEqual(branch, _.intersection(path, branch)));
if (!isSubpath) {
paths.push(branch);
}
});
For the example above, this returns the following:
[[4,3,2,1,6], [8,5,2,1]]
I've also tested with more "branching", like example:
P = {1:[[]], 2:[[1]], 3:[[2]], 4:[[3]], 5:[[2]], 6:[[]], 7: [[4,6],[8],[5]], 8:[[6],[3]]}
Which returns:
[[4,3,2,1,6],[8,6],[8,3,2,1],[5,2,1]]
For now its working, but....as I said, I think its more complicated than it needs to be. So, any improvements are welcome.
Related
What I am Doing
I am trying to create a Sudoku solver and generator in Vue. Right now, I have the solving algorithm set up, and just need to generate new problems. I am generating problems by creating a completed Sudoku problem (complete with no bugs), then I have to remove nodes so that there is still only 1 solution to the problem.
The Problem
When I try to access a node from the multi-dimensional array that represents the board, and change it to null (what I am using to display a blank node), the board does not update that value. I am changing it with the following code: newGrid[pos[0]][pos[1]] = null; (where pos[0] is the row, pos[1] is the column , and newGrid is grid we want to mutate). Note that the array is an array with 9 arrays inside, and each of those arrays has 9 numbers (or null) which represent the values for that position in the grid. To elaborate on the bug, if I put a console.log(newGrid), there are normal looking values, and no null.
What I Know and Have Tried
I know it has to do with this specific line, and the fact that I am setting the value equal to null because changing null to another value (i.e. newGrid[pos[0]][pos[1]] = 0;) works and changes the array. The reason I don't just use a value other than null is: null renders and nothing and other values (0) render as something (null nodes should be blank), null is simple to understand in this situation (the logic is node has null, node has nothing, node is blank), and null is already implemented throughout my codebase.
Additionally, if I use console.log(newGrid[pos[0]][pos[1]]), null (the correct output) is outputted, even though console.log(newGrid) shows a number there, not null. Also, oddly enough, this works for one specific node. In row 1 (indexing starts at 0), column 8, null is set. Even though the input (completed) grid is always different, this node is always set to null. Edit: this bug had to do with the input grid already having null here, so it actually doesn't let any nulls be set.
To summarize: I expect an array with a null in a few positions I update, but I get a number instead. Also, there are no errors when the Typescript compiles to Javascript or during runtime.
Code
Given that I am not exactly sure where the problem may be (i.e. maybe I create the array wrong) I am including the minimum code with a pastebin link to the whole file (this is the full code). To restate, the goal of this function is to remove nodes from the list (by replacing them with null) in order to create a Sudoku puzzle with one solution. The code on Stack Overflow only includes some of the whole file, and the pastebin link includes the rest.
//global.d.ts
type Nullable<T> = T | null;
type Grid = Array<Array<number | null>>;
import { Solver } from './Solve';
// Inside the function that does the main work
const rowLen: number = grid.length;
const colLen: number = grid[0].length;
let newGrid: Grid = grid; // Grid is a argument for this function
let fullNodes = GetFirstFull(grid, colLen, rowLen);
let fullNodesLen: number = fullNodes.length;
// Some stuff that figures out how many solutions there are (we only want 1) is excluded
if (solutions != 1) {
fullNodesLen++;
rounds--;
} else {
newGrid[pos[0]][pos[1]] = null;
}
Note that if anything seems confusing check out the pastebin or ask. Thank you so much for taking the time to look at my problem!
Also, it isn't just 0 that works, undefined also makes it set correctly. So, this problem seems to be something with the null keyword...
EDIT:
Given that no one has responded yet, I assume: my problem is a bit hard, there isn't enough information, my post isn't good quality, or not enough people have seen it. To control the problem of not enough information, I would like to include the function that calls this function (just to see if that might be related).
generate(context: ActionContext<State, any>) {
let emptyArray = new Array(9);
for (let i = 0; i < 9; ++i)
emptyArray[i] = [null, null, null, null, null, null, null, null, null];
const fullGrid = Solver(emptyArray);
const puzzle = fullGrid ? Remover(fullGrid, 6) : state.gridLayout;
context.commit('resetBoard', puzzle);
},
Note: If you aren't familiar with Vuex, what context.commit does is changes the state (except it is changing a global state rather than a component state). Given that this function isn't refactored or very easy to read code in the first place, if you have any questions, please ask.
To solve other potential problems: I have been working on this, I have tried a lot of console.log()ing, changing the reference (newGrid) to a deepcopy, moving stuff out of the if statements, verifying code execution, and changing the way the point on the newGrid is set (i.e. by using newgrid.map() with logic to return that point as null). If you have any questions or I can help at all, please ask.
I am working on Laravel + Vue and I've been stuck in the process of finding the least node in a tree..
This image you will see below is the structure. In one node there must be 3 sub-nodes if he got a 4th one, he, the new node will fill-in in the least sub-nodes below
IMAGE HERE
I already implemented for the level 3 part but I am struggling on what should I do if ever the new node will fill-in in the least sub-nodes of level 4 nodes and level 5 up to level 7?
Anyone can share their knowledge to work make this work?
here's what I got so far
getMemberHasLowestMember(data) {
// get the lowest number of members count
let lowest_number_of_members = data.reduce((min, b) => Math.min(min, b.members.length), data[0].members.length)
// get the members who have the lowest number of members
let member_has_low_members = data.filter(member => member.members.length == lowest_number_of_members)
if(member_has_low_members.length > 1) {
// get the random number from length of members_has_low_members
let random_number = Math.floor(Math.random() * Math.floor(member_has_low_members.length))
return member_has_low_members[random_number]
} else {
return member_has_low_members[0]
}
},
In this case, I have 1 user data and it has teams object and in that object it has members but as the object go deeper, I still don't know how to get team member's own members until level 7
I am trying to create a wall with 2 layers and each layer materials are different. When I try to set the CompoundStructure for the wall I am getting an exception that CompoundStructure is not valid.
CompoundStructure cStructure = CompoundStructure.CreateSimpleCompoundStructure(clayer);
wallType.SetCompoundStructure(cStructure);
Can anyone tell me how I can create compound structure for layers with different materials?
First of all, solve your task manually through the end user interface and verify that it works at all.
Then, use RevitLookup and other database exploration tools to examine the results in the BIM elements, their properties and relationships.
Once you have done that, you will have a good idea how to address the task programmatically – and have confidence that it will work as expected:
How to research to find a Revit API solution
Intimate Revit database exploration with the Python Shell
newWallMaterial = wallMaterial.Duplicate("newCreatedMaterial");
newWallmaterial2 = wallMaterial.Duplicate("NewCreatedMAterial2");
//roofMaterial3 = roofMaterial2.Duplicate("NewCreatedMAterial3");
bool usr = newWallMaterial.UseRenderAppearanceForShading;
//newWallMaterial.Color = BuiltInTypeParam.materialCol;
foreach (Layers layer in layers)
{
if (layer.layerId == 0)
{
c = new CompoundStructureLayer(layer.width, layer.materialAssignement, newWallMaterial.Id);
newWallMaterial.Color = color;
clayer.Add(c);
}
if (layer.layerId == 1)
{
c1 = new CompoundStructureLayer(layer.width, layer.materialAssignement, newWallmaterial2.Id);
newWallmaterial2.Color = color;
clayer.Add(c1);
}
I'm building an application which uses jointjs / rappid and I want to be able to avoid loops from occuring across multiple cells.
Jointjs already has some examples on how to avoid this in a single cell (connecting an "out" port to an "in" port of the same cell) but has nothing on how to detect and prevent loops from occuring further up in the chain.
To help understand, imagine each cell in the paper is a step to be completed. Each step should only ever be run once. If the last step has an "out" port that connects to the "in" port of the first cell, it will just loop forever. This is what I want to avoid.
Any help is greatly appreciated.
I actually found a really easy way to do this for anyone else who wishes to achieve the same thing. Simply include the graphlib dependancy and use the following:
paper.on("link:connect", function(linkView) {
if(graphlib.alg.findCycles(graph.toGraphLib()).length > 0) {
linkView.model.remove();
// show some error message here
}
});
This line:
graphlib.alg.findCycles(graph.toGraphLib())
Returns an array that contains any loops, so by checking the length we can determine whether or not the paper contains any loops and if so, remove the link that the user is trying to create.
Note: This isn't completely full-proof because if the paper already contains a loop (before the user adds a link) then simply removing the link that the user is creating won't remove any loop that exists. For me this is fine because all of my papers will be created from scratch so as long as this logic is always in place, no loops can ever be created.
Solution through graphlib
Based on Adam's graphlib solution, instead of findCycles to test for loops, the graphlib docs suggests to use the isAcyclic function, which:
returns true if the graph has no cycles and returns false if it does. This algorithm returns as soon as it detects the first cycle.
Therefore this condition:
if(graphlib.alg.findCycles(graph.toGraphLib()).length > 0)
Can be shortened to:
if(!graphlib.alg.isAcyclic(graph))
JointJS functions solution
Look up the arrays of ancestors and successors of a newly connected element and intersect them:
// invoke inside an event which tests if a specific `connectedElement` is part of a loop
function isElementPartOfLoop (graph, connectedElement) {
var elemSuccessors = graph.getSuccessors(connectedElement, {deep: true});
var elemAncestors = connectedElement.getAncestors();
// *** OR *** graph.getPredecessors(connectedElement, {deep: true});
var commonElements = _.intersection(elemSuccessors, elemAncestors);
// if an element is repeated (non-empty intersection), then it's part of a loop
return !_.isEmpty(commonElements);
}
I haven't tested this, but the theory behind the test you are trying to accomplish should be similar.
This solution is not as efficient as using directly the graphlib functions.
Prevention
One way you could prevent the link from being added to the graph is by dealing with it in an event:
graph.on('add', _.bind(addCellOps, graph));
function addCellOps (cell, collection, opt) {
if (cell.isLink()){
// test link's target element: if it is part of a loop, remove the link
var linkTarget = cell.getTargetElement();
// `this` is the graph
if(target && isElementPartOfLoop(this, linkTarget)){
cell.remove();
}
}
// other operations ....
}
I am trying to execute parallel functions on a list of objects using the new C# 4.0 Parallel.ForEach function. This is a very long maintenance process. I would like to make it execute in the order of the list so that I can stop and continue execution at the previous point. How do I do this?
Here is an example. I have a list of objects: a1 to a100. This is the current order:
a1, a51, a2, a52, a3, a53...
I want this order:
a1, a2, a3, a4...
I am OK with some objects being run out of order, but as long as I can find a point in the list where I can say that all objects before this point were run. I read the parallel programming csharp whitepaper and didn't see anything about it. There isn't a setting for this in the ParallelOptions class.
Do something like this:
int current = 0;
object lockCurrent = new object();
Parallel.For(0, list.Count,
new ParallelOptions { MaxDegreeOfParallelism = MaxThreads },
(ii, loopState) => {
// So the way Parallel.For works is that it chunks the task list up with each thread getting a chunk to work on...
// e.g. [1-1,000], [1,001- 2,000], [2,001-3,000] etc...
// We have prioritized our job queue such that more important tasks come first. So we don't want the task list to be
// broken up, we want the task list to be run in roughly the same order we started with. So we ignore tha past in
// loop variable and just increment our own counter.
int thisCurrent = 0;
lock (lockCurrent) {
thisCurrent = current;
current++;
}
dothework(list[thisCurrent]);
});
You can see how when you break out of the parallel for loop you will know the last list item to be executed, assuming you let all threads finish prior to breaking. I'm not a big fan of PLINQ or LINQ. I honestly don't see how writing LINQ/PLINQ leads to maintainable source code or readability.... Parallel.For is a much better solution.
If you use Parallel.Break to terminate the loop then you are guarenteed that all indices below the returned value will have been executed. This is about as close as you can get. The example here uses For but ForEach has similar overloads.
int n = ...
var result = new double[n];
var loopResult = Parallel.For(0, n, (i, loopState) =>
{
if (/* break condition is true */)
{
loopState.Break();
return;
}
result[i] = DoWork(i);
});
if (!loopResult.IsCompleted &&
loopResult.LowestBreakIteration.HasValue)
{
Console.WriteLine("Loop encountered a break at {0}",
loopResult.LowestBreakIteration.Value);
}
In a ForEach loop, an iteration index is generated internally for each element in each partition. Execution takes place out of order but after break you know that all the iterations lower than LowestBreakIteration will have been completed.
Taken from "Parallel Programming with Microsoft .NET" http://parallelpatterns.codeplex.com/
Available on MSDN. See http://msdn.microsoft.com/en-us/library/ff963552.aspx. The section "Breaking out of loops early" covers this scenario.
See also: http://msdn.microsoft.com/en-us/library/dd460721.aspx
For anyone else who comes across this question - if you're looping over an array or list (rather than an IEnumberable ), you can use the overload of Parallel.Foreach that gives the element index to maintain original order too.
string[] MyArray; // array of stuff to do parallel tasks on
string[] ProcessedArray = new string[MyArray.Length];
Parallel.ForEach(MyArray, (ArrayItem,loopstate,ArrayElementIndex) =>
{
string ProcessedArrayItem = TaskToDo(ArrayItem);
ProcessedArray[ArrayElementIndex] = ProcessedArrayItem;
});
As an alternate suggestion, you could record which object have been run and then filter the list when you resume exection to exclude the objects which have already run.
If this needs to be persistent across application restarts, you can store the ID's of the already executed objects (I assume here the objects have some unique identifier).
For anybody looking for a simple solution, I have posted 2 extension methods (one using PLINQ and one using Parallel.ForEach) as part of an answer to the following question:
Ordered PLINQ ForAll
Not sure if question was altered as my comment seems wrong.
Here improved, basically remind that parallel jobs run in out of your control order.
ea printing 10 numbers might result in 1,4,6,7,2,3,9,0.
If you like to stop your program and continue later.
Problems alike this usually endup in batching workloads.
And have some logging of what was done.
Say if you had to check 10.000 numbers for prime or so.
You could loop in batches of size 100, and have a prime log1, log2, log3
log1= 0..99
log2=100..199
Be sure to set some marker to know if a batch job was finished.
Its a general aprouch since the question isnt that exact either.