interprocess | platform shared memory queue for fast communication
kandi X-RAY | interprocess Summary
kandi X-RAY | interprocess Summary
Here are a couple of items that we are working on.
Support
Quality
Security
License
Reuse
Top functions reviewed by kandi - BETA
Currently covering the most popular Java, JavaScript and Python libraries. See a Sample of interprocess
interprocess Key Features
interprocess Examples and Code Snippets
Community Discussions
Trending Discussions on interprocess
QUESTION
#include
#include
#include
#include
#include
int funcone(){
int i;
char *arr[5] = {"One", "Two", "Three", "Four", "Five"};
for(i = 0; i <= 5; i++){
printf("%s\t%d\n", arr[i], i);
}
printf("\n~");
return 1;
}
#define NCHAR 1024
#define DELIMIT "\t\n"
int functwo(){
//prints only numbers from input received from funcone
int c;
int position = 0, nchar = NCHAR, i;
char *arr = malloc(sizeof *arr * nchar);
if (!arr)
{
fprintf(stderr, "Memory Exhausted.");
}
//reads input from stdin stream, supposedly piped from func1
while ((c = fgetc(stdin)) != 126)
{
arr[position++] = c;
if (position >= nchar) // reallocate space if needed
{
nchar += NCHAR;
arr = realloc(arr, nchar + NCHAR);
if (!arr)
{
fprintf(stderr, "Memory Exhausted.\n");
break;
}
}
}
arr[position] = 0;
char *token;
//splits string by \t\n, and converts string into numbers
token = strtok(arr, DELIMIT);
while (token != NULL)
{
char *endptr;
int x = strtol(token, &endptr, 10);
if (x > 0)
{
printf("%d\n", x);
}
token = strtok(NULL, DELIMIT);
}
printf("\n~");
free(arr);
return 1;
}
int main(){
printf("piping begins\n");
int fd[2];
int childstatus = 0;
if (pipe(fd) == -1)
{
perror("Pipe1 error");
return 1;
}
int pid1 = fork();
if (pid1 < 0)
{
perror("Pid1 error");
return 1;
}
if (pid1 == 0)
{
//child 1 process
dup2(fd[1], STDOUT_FILENO);
close(fd[1]);
close(fd[0]);
int f1 = funcone();
// int f1 = (*builtin_functions[aone])(argone);
/*In the main program, this line runs a function
*with a corresponding index number, and takes in the
*command keywords as arguments. Returns 1 to continue Shell loop, 0 to exit.*/
}
int pid2 = fork();
if (pid2 < 0)
{
perror("Pid2 error");
return 1;
}
if (pid2 == 0)
{
// child 2 process
dup2(fd[0], STDIN_FILENO);
dup2(fd[1], STDOUT_FILENO);
close(fd[0]);
close(fd[1]);
int f2 = functwo();
// int f1 = (*builtin_functions[aone])(argone);
}
// parent process
waitpid(pid1, &childstatus, WNOHANG);
waitpid(pid2, &childstatus, WNOHANG);
dup2(fd[0], STDIN_FILENO);
close(fd[0]);
close(fd[1]);
int f3 = functwo();
//supposed to be functhree, but something similar to functwo so i reused it.
// int f3 = (*builtin_functions[aone])(argone);
printf("Piping process complete.\n");
}
ANSWER
Answered 2022-Mar-22 at 13:53Your first child process is writing to the pipe. Your parent process and second child process are both reading from that same pipe. Each byte written to the pipe will be consumed by one of those latter two processes, but you have no direct control over which one. This is not inherently wrong, but it is rarely what you want, and it will not work reliably for you in the example program.
What likely is happening is that the parent process consumes the data written by the first process, or at least the end-of-message character, which you intend for the second child instead. The second child then waits forever to read data that will never arrive. It does not even detect end-of-file on the pipe when the first child terminates, because the second child itself holds the write end of the pipe open. The parent, in turn, waits forever for the second child to terminate.
Supposing that the intention is for the second child to consume all the data written by the first child, and for the parent to in turn consume all the data written by the second child, you should create a separate pipe for the child2 --> parent link. That's usually the pattern you want: a separate pipe for each distinct ordered pair of endpoints. That includes a separate pipe for each direction if you want bidirectional communication between the same two processes.
Update:Additionally, funcone() overruns the bounds of its local arr array. The valid indices are 0 through 4, but the for loop in that function runs from 0 through 5.
QUESTION
I have a process which is using boost message queue. When it is being blocked in either send or receive due to queue size limit has been reached, if I send a signal, it seemed the function call remained blocking. I expected the call to cancel or raise an exception but it didn't behave that way. How can I interrupt the send or receive function call ?
ANSWER
Answered 2022-Feb-04 at 00:16The way is to use the timed interfaces:
QUESTION
This question had conflicting answers: Are Python multiprocessing Pool thread safe?
I am new to concurrency patterns and I am trying to run a project that takes in an array and distributes the work of the array onto multiple processes. The array is large.
...ANSWER
Answered 2021-Dec-28 at 04:17- With the code provided, it is impossible that the same item of
inputswill be processed by more than one process (an exception would be if the same instance of an object appears more than once in the iterable passed as argument). Nevertheless, this way of using multiprocessing has a lot of overhead, since theinputsitems are sent one by one to the processes. A better approach is to use thechunksizeparameter:
QUESTION
In order to get around growing a managed_shared_memory segment without unmapping and remapping all the previous regions, I want to create an allocator that creates a new managed_shared_memory segment whenever there is not enough space in the previous segments. I have looked into the boost interprocess node allocators but they don't seem like a good fit for this problem. Is there any class or utility in boost that can help with this problem?
...ANSWER
Answered 2021-Dec-20 at 16:03Not a direct match to the question, but the relevant fruit of the comment thread, here I present an example that uses managed_external_buffer to achieve more control over on-disk format (foreseeing backwards compatible versioning and perhaps some integrity verification) and shows how to implement growth
QUESTION
.NET 6 has trouble calling its own IDispatch objects, if marshaled.
To reproduce:
...ANSWER
Answered 2021-Dec-13 at 14:19Here's what is going on. The .NET object supports two dispinterfaces - one corresponding to IHello, another corresponding to Hello itself, and the latter is treated as the default one. I've confirmed that by adding an extra method Bar() to Hello, and checking the type in a native C++ client:
QUESTION
I'm learning interprocess communication through messages.
In the following code snippet, I apply fork() and send messages between the parent and the child processes.
I expect "1 - 2 - 3 - 4" console output. However, I got "1 - 2", and after this, the program seems to be stuck forever on the msgrcv line before printing "3". Could anyone tell what's wrong with the code?
ANSWER
Answered 2021-Nov-20 at 00:17The problem is with the message type initialization here:
QUESTION
I've got a Boost:interprocess::unordered_map that has a Key of type string and Value of type string. That map is stored in a managed_shared_memory segment. I'm attempting to restrict access to these segments, so the segment is created with rw-rw-r--. The idea is the owner and related group would have read/write access, and 'other' would be restricted to read only.
This works fine if I open_read_only and iterate through the map manually. All of the data is present across processes. I ran into issues when attempting to use mymap->find() or mymap->at(), because both functions require the basic_string (w/ allocator) be passed.
When I attempt to create a basic_string to use in find() or at(), I get an access violation error.
...ANSWER
Answered 2021-Nov-11 at 23:30You never check the pointer mymap is not null.
If we make sure that exists, by first executing this (once):
QUESTION
I am using a boost::interprocess::deque with a memory_mapped_file as a file buffer that lets data survive reboots etc.
I am creating the buffer like this:
...ANSWER
Answered 2021-Nov-10 at 18:27Firstly: add some peace and quiet to your code :)
QUESTION
In a cross platform (Linux and windows) real-time application, I need the fastest way to share data between a C++ process and a python application that I both manage. I currently use sockets but it's too slow when using high-bandwith data (4K images at 30 fps).
I would ultimately want to use the multiprocessing shared memory but my first tries suggest it does not work. I create the shared memory in C++ using Boost.Interprocess and try to read it in python like this:
...ANSWER
Answered 2021-Sep-15 at 19:53So I spent the last days implementing shared memory using mmap, and the results are quite good in my opinion. Here are the benchmarks results comparing my two implementations: pure TCP and mix of TCP and shared memory.
Protocol:Benchmark consists of moving data from C++ to Python world (using python's numpy.nparray), then data sent back to C++ process. No further processing is involved, only serialization, deserialization and inter-process communication (IPC).
Case A:
- One C++ process implementing TCP communication using Boost.Asio
- One Python3 process using standard python TCP sockets
Communication is done with TCP {header + data}.
Case B:
- One C++ process implementing TCP communication using Boost.Asio and shared memory (mmap) using Boost.Interprocess
- One Python3 process using standard TCP sockets and mmap
Communication is hybrid : synchronization is done through sockets (only header is passed) and data is moved through shared memory. I think this design is great because I have suffered in the past from problem of synchronization using condition variable in shared memory, and TCP is easy to use in both C++ and Python environments.
Results: Small data at high frequency200 MBytes/s total: 10 MByte sample at 20 samples per second
Case Global CPU consumption C++ part python part A 17.5 % 10% 7.5% B 6% 1% 5% Big data at low frequency200 MBytes/s total: 0.2 MByte sample at 1000 samples per second
Case Global CPU consumption C++ part python part A 13.5 % 6.7% 6.8% B 11% 5.5% 5.5% Max bandwidth- A : 250 MBytes / second
- B : 600 MBytes / second
In my application, using mmap has a huge impact on big data at average frequency (almost 300 % performance gain). When using very high frequencies and small data, the benefit of shared memory is still there but not that impressive (only 20% improvement). Maximum throughput is more than 2 times bigger.
Using mmap is a good upgrade for me. I just wanted to share my results here.
QUESTION
I am using shared memory provided by boost/interprocess/ to share the cv::Mat between model and client (both C++). Now I need to use a model in Python. Can you please tell which is the best way to share the cv::Mat between C++ and Python without changing the present client. Thanks.
...ANSWER
Answered 2021-Nov-02 at 06:35The task was completed using mapped memory to share the cv::Mat between C++ and Python process.
- C++ - use boost to copy cv::Mat to a mapped shared memory
Community Discussions, Code Snippets contain sources that include Stack Exchange Network
Vulnerabilities
No vulnerabilities reported
Install interprocess
Support
Reuse Trending Solutions
Find, review, and download reusable Libraries, Code Snippets, Cloud APIs from over 650 million Knowledge Items
Find more librariesStay Updated
Subscribe to our newsletter for trending solutions and developer bootcamps
Share this Page
