nbody | Fast n-body gravitational simulation code
kandi X-RAY | nbody Summary
kandi X-RAY | nbody Summary
Fast n-body gravitational simulation code, written in C++ with ports to other slower languages. Currently supported languages: C++, Python.
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QUESTION
I've been working on an application which contains a small, simple http server to handle post requests on occasion. The server and all functionality around it works fine, but each time the server runs, log output would tell me that my code is being run multiple times, plus one time for each request the http server handles.
...ANSWER
Answered 2021-May-11 at 00:39It turns out that this wasn't an issue with my code, but rather an issue with the logger I was using which was adding multiple console handlers for the same logger, causing output to be repeated. I fixed this in my cli library.
QUESTION
I am trying to write just a simple program to simulate an N-Body system using python (and pygame for GUI just because I have more experience than tk). The issue I am running into is I made a body class that is a subclass from a sprite. I have an adaptable list size of n that appends that many bodies into the list. To start I just decided to have updates be performed in a double for loop with a final for loop that passes the updates after they have been calculated (I know this is not efficient, not the point). My issue is that when I pass an update to an element of this list, the update is applied to every thing in that list. What is going on here? Why are these completely separate elements tied together? Necessary code below
Body class
...ANSWER
Answered 2021-Mar-16 at 15:32See Class and Instance Variables:
Generally speaking, instance variables are for data unique to each instance and class variables are for attributes and methods shared by all instances of the class.
Since val and acc are class attributes they are shared by all Body objects and as you mentioned in your question: "these completely separate elements tied together".
vel and acc have to be instance attribute instead of class attributes:
QUESTION
This an MPI version of the NBody problem. I already have an OpenMP version and its results are the same as the nbody version with one thread, but the MPI results differ, above all at the last interactions. At the first interactions, the outputs are quite similar but at the end, the outputs differ a lot.
...ANSWER
Answered 2021-Feb-03 at 19:48You get different results because your algorithm is solving a completely different problem when running with more than one MPI rank.
You are performing domain decomposition by splitting the array of particles in parts, and then each rank computes the forces only taking into account the particles in its own subdomain:
QUESTION
I've implemented a simple direct Nbody simulation in python. I'm looking to parallelize it as we are doing the same operation again and again. In C++, I would have use openmp, but python doesn't have it.
So I was thinking to use the multiprocessing module. From what I understand, I would need a manager to manage the class (and the list particles?) and I was thinking of using a starmap pool.
I'm quite lost on how to use these function to achieve any semblance of parallelization, so any help is appreciated.
PS: I'm open to use other module too, the easier the better. The class is ditchable if using numpy array (for position velocity mass) solves the problem, I'll go with it.
Code:
...ANSWER
Answered 2021-Jan-28 at 03:14If you want to share a list of custom objects (such as particle in the question) among processes, you can consider a simplified example here:
QUESTION
Hello I hope you are well. Recently, I have a problem using the Twitter API precisely at the time of publishing a tweet. According to the documentation here, my request must contain in its header a field oauth_timestamp which is the number of seconds since the epoch(seconds since the Unix epoch).
With Dart(Flutter) I retrieve the number of milliseconds elapsed since the epoch which I then divide by 1000 to obtain this value in seconds. Ex:
...ANSWER
Answered 2021-Jan-13 at 15:12I solved the problems that prevented me from publishing a tweet using the Twitter API.
First of all: I kept my way of retrieving elapsed time (in seconds) since epoch
QUESTION
For some unknown reason, I can't make getChild work for a nested element.
Here's my sample Apps Script Code:
ANSWER
Answered 2021-Jan-08 at 13:47The element you want has a different namespace than the root.
QUESTION
I have my views file:
...ANSWER
Answered 2020-Oct-29 at 06:02A MultiValueDictKeyError comes when you try to access something from request.POST which doesn't exist. It's basically the same the python KeyError. Use request.POST.get('key', 'default_if_key_doesn't exist')
QUESTION
I am trying install Cuda on WSL 2. I am following instructions such as this.
After executing every step, I try to check if gpu is available in the Linux environment by executing docker run --gpus all nvcr.io/nvidia/k8s/cuda-sample:nbody nbody -gpu -benchmark (as suggested by the aforementioned instructions).
But I get the following error:
docker: Error response from daemon: could not select device driver "" with capabilities: [[gpu]].
ERRO[0000] error waiting for container: context canceled.
Any ideas what might be the cause of this?
...ANSWER
Answered 2020-Jun-20 at 10:20I was having the same issue. Are you using Docker Desktop for Windows? Because I was, and I found out that WSL2 + CUDA does not work with Docker Desktop for Windows:
https://forums.developer.nvidia.com/t/hiccups-setting-up-wsl2-cuda/128641
Instead, install Docker manually in WSL2 (as is suggested in the tutorial you linked):
QUESTION
import java.util.Scanner;
public class NoteIt {
public static void main(String[]args) {
Scanner s = new Scanner(System.in);
int Answer;
int i=2;
System.out.print("\nPlease Enter your Name: ");
String Name = s.nextLine();
System.out.println("Welcome to Note-It "+Name+", We hope you'll enjoy our application. ");
String[][] Main = new String[2][2];
Main[0][0]="Create new Note";
Main[1][0]="View My Notes";
System.out.println("\nPlease select what to do: \n");
for(int n=0; n<2; n++){
System.out.println((n+1)+") "+Main[n][0]);
}
System.out.print("\nPlease enter your response: ");
Answer = s.nextInt();
if(Answer == 1){
i++;
Main = new String[i][2];
System.out.print("\nTitle: ");
Main[i-1][0]=s.nextLine();
System.out.print("\nBody: ");
Main[i-1][1]=s.nextLine();
}
}
}
ANSWER
Answered 2020-Sep-10 at 10:03According to @Rohit Jain, That's because the Scanner.nextInt method does not read the newline character in your input created by hitting "Enter," and so the call to Scanner.nextLine returns after reading that newline.
Description here: check this question too
Try this it may help...
QUESTION
I have a post server written in python3.6.9, running on the localhost behind an apache2 reverse proxy. It receives a base64 file uploaded via Powershell and decodes them. Text Files get saved to the directory ./Public/example.txt. If bytes are uploaded, it handles the error with 'except binascii.Error' and I can properly write it to the directory. Both file types saved this way do so by taking the URI and replacing '/store.json' with nothing. If no FileName is present in post data, an 'except IOError' will write it to ./store.json in the current directory.
Here is the main code:
...ANSWER
Answered 2020-Aug-04 at 04:28First off welcome to SO.
So a few things that may help you out. People don't usually use python's HTTPServer unless you're wanting to control the lower part of http request and response. If you want to use a easy to use/setup http server flask is a great option as it will handle parsing POST data as well as saving files when they come through.
Q1. Is there a better way to identity files?
A1. This depends. During an http request to upload a file http standard is to upload the file name and extension along with the file's bytes. If you only upload bytes then most http servers will just ignore it and return an error. So if you send the name and extension along with the bytes than you know what kind of data it is and how to store it.
Also base64 is an encoding. So the only way to know if the encoding is good or not (malformed/dropped bytes) is to actually try and decode it and then catch any errors when it finds them. There is no way of asking it if it's a valid encoding without it actually trying to decode the data.
Q2. Can you blindly handle errors in python?
A2. Yes you can though it is discouraged to do so.
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