Software :: Shared Memory Between Fortran & C++ Applications?
May 7, 2010
I have to figure out how to pass data between a Fortran application and a C++ application. The memory has to be locked/unlocked to prevent data corruption. I know very little about Fortran. I have done mutex lock/unlock stuff in Linux apps, multi-threaded, using mutex locks before.
Digging around on the Web, I do not find any info on a Fortran app including linux headers, library calls such as those in ipc.h, shm.h and sem.h. What is an approach to this problem?
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Jun 14, 2010
I have a problem when I want to run executable program,I get this:
./xtramp: error while loading shared libraries: libf2c.so.2: cannot open shared object file: No such file or directory. My machine is x86_64,may be ere is problem.Anu ideas how to solve this?
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Jun 11, 2010
I want to create a "Shared Memory" in linux, then create multiple "Shared Objects" that can access to a Table for example; And one of them can write something into the Table and the other can access and read it, so that these operations can be handled by programmer! I'm using Ubuntu 9.04 and I've set it's runlevel at 3 (I have commandline environment now!) I've searched the Internet so much, but couldn't find a good sample code for this! I have no experience about it and need your help to introduce me a sample code about it and advise me how to compile and use it with "GCC"?!
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Apr 19, 2010
I have 2 applications that send and receive messages through shared memory IPC. When I run the app ..it works but the number of messages per sec keeps changing drastically sometimes it is 400-500 per sec..then 800 then 1200 then 2000. is this normal with SHM IPC or could it be a code related issue.
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Feb 4, 2011
how come shared memory is only using 4 gigs of ram?
Code:
localhost router # free -m
total used free shared buffers cached
Mem: 8001 858 7142 0 130 235
-/+ buffers/cache: 492 7508
[code]...
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Apr 20, 2010
I am trying to troubleshoot an Apache/Mysql server that once every few days falls over due to memory starvation. I thought I had tuned my httpd.conf file with relativley small MaxClients and so on, but then noticed some unusual RES values in top while monitoring.
In short, `top -b -n1 -u apache` shows that I have 28 httpd processes. their VIRT is ~300MB for each process (I understand this is shared), and the RES ~50MB for each. I thought this wasn't shared. Is this true? I just noticed 2 of the processes jump to 1.2g. If RES represents non-shared memory then concievably 1.2g x 28 processes would be a problem on an 8GB server.
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Jul 16, 2010
Does anyone know if there is a size limitation for shared-memory segments in RHEL AS 4?
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Apr 5, 2010
I'm running a Debian based distro.
When I run ipcs this pops up:
This happens only while KDE3 is running. Regardless of the runlevel, if kdm is not started, this will not show.
By running ipcs -p the PID points to process
Is there anything wrong with that command?
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Aug 20, 2010
When I boot into Linux i see some shared memory which is blocked, due to this I am unable to start my processes which needs some shared memory.I tried removing the shared memory using ipcrm -m but no use, the shared memory is not cleaned but its still in use.I tried removing the shared memory using root user also normal user but unable to remove the shared memory.
[pin01]$ ipcs -m
------ Shared Memory Segments --------
key shmid owner perms bytes nattch status
[code]...
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Jun 1, 2009
Any good tutorial on sharing dynamically allocated objects across shared libraries in the same process and between shared libaries and main(). In particular, I need to know what creation and destruction sequences are valid when libraries are being loaded and unloaded. For example, is it valid to allocate an object from inside a shared library procedure, and then delete that pointer from a different module, especially in the case where the allocating module has already been unloaded.
I imagine there might be all kinds of problems with this. Although my preliminary tests seem to work most of the time, I get crashes from time to time, but I'm not sure if they're caused by memory management or by threading issues. I've been restructuring my code to use a global context object to manage object creation and destruction from main(), but I'd like to find a clear exposition of the specific issues I'm dealing with before I go too much further.
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Jan 8, 2011
I'm writing a producer-consumer program, where the producer and the consumer are different processes and they communicate using queued signals, and when I run it it comes out always 'segmentation fault'.
Here is my code:
(note: I tried using both 'shm_open()' and 'mmap()', and 'shmget()' and shmat()')
Code:
#include <stdio.h>
#include <stdlib.h>
#include <signal.h>
[code]....
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Mar 17, 2010
So I'll try to be brief and to the point here: I've got a couple of C / C++ apps that communicate with one another via shared memory. These worked completely fine until.. well, about twenty minutes ago when I finished making some network card changes and suddenly, I've got a weird problem going on. At one point, Parent app waits for Child app to set a boolean indicating it's finished initialization. This worked fine the last time I ran this app up (a few days ago). But right now, the shared flag never seems to get triggered (I've added a printf("Waiting..."); in Parent app until the flag is set). All the code leading up to it being set in Child app seem to be running smoothly, so I tried spitting out the addresses of the shared memory locations. The addresses mapped by Parent app and Child app are different; this seemed odd, so I went back and wrote a simple miniature app that just opened a shared structure on my own box, and I get the same thing - different addresses - but the miniature apps work just fine.
Is it normal for a shared memory space to be mapped to two different addresses across two processes?
If so, does anyone have any idea what might be the issue at hand with my Parent / Child app scenario? The Child creates the shared memory, the Parent has a wait before it opens it, and if it doesn't exist should fail (opening with PROT_READ | PROT_WRITE)... it doesn't fail so it's evidently there.
All of this worked until literally just a few hours ago and I made some changes to my network cards, and I can't even imagine how that could have changed whether or not shared memory mapping worked...
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Aug 13, 2010
When the systen is running there is a program/utility/kernel-driver? kthreadd in system monitor all the following programs are a child process of kthreadd. Is kthreadd part of elevator=cfq and can kthreadd be influenced by params. kthreads uses no cpu time memory or shared memory so it must be in kernel. is there any documentation on this subject? System 11.3 on quad processor 8 gb mem nvidia-card and driver.
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Jul 17, 2011
How do I change the size of the available shared memory on Linux?evidently 4GB is not enough for what I am doing (I need to load a lot of data into shared memory - my machine got 8GB of RAM).
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Feb 5, 2011
I have what should be a relatively simple program (fadec.c) that maps a struct from an included header file (fadec.h) to a shared memory region, but Im struggling accessing members in the struct from the pointer returned by shmat. Ultimately, I want to access members in the shared memory structure with a globally declared version of the struct, shm__. Not only do I not know how to accomplish that, but I cant even seem to access members of the shared struct directly from the pointer itself (compiler complains about dereferencing pointer to incomplete type). Im at a loss and could use another set of eyes if you guys dont mind taking a gander:
Compile Errors:
tony-pc:/cygdrive/p/test> cc -o fadec fadec.c
fadec.c: In function 'main':
fadec.c:30: error: dereferencing pointer to incomplete type
fadec.c:31: error: dereferencing pointer to incomplete type
[Code]...
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May 17, 2011
My problem is I installed Zone Minder for camera security and I'm testing it on my laptop with the built in webcam and everything seems to work perfectly except when I try to view the live feed from the camera, it's just a black box. No video.
I checked this website and it's exactly the problem I'm having with a fix for it but his fix doesn't work. He says to type:
Code:
user@ubuntu:~$ sudo echo "256000000" > /proc/sys/kernel/shmmax
user@ubuntu:~$ sudo service apache2 restart
user@ubuntu:~$ sudo service zoneminder restart
But when I do the first line, I get this:
Code:
deemar@Clementine:~$ sudo echo "256000000" > /proc/sys/kernel/shmmax
bash: /proc/sys/kernel/shmmax: Permission denied
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Jan 12, 2010
I just opened an (unmanaged) VPS account and and have been encountering nothing but problems with trying to get Apache up and running (its something I've done many times before).Basically the inital error was with LDAP not having enough space, so I disabled the related extensions and Apache still would not run. Looking at the log, it contains: (28)No space left on device: Unable to create scoreboard (anonymous shared memory failure)
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Nov 30, 2010
I need to find the memory usage of a shared library loaded in Linux environment.
I need this information for deciding on whether to make the library part in to application or a seperate application itself.
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Mar 4, 2011
I have a program that creates and uses a shared memory segment. I am trying to find out how to detach and delete this shared memory segment when I hit crtl-C, and I still need the process to terminate.shmdt() and shmctl() have variables that are local to the main passed to them(shared and shmid)
Code:
//Prototype
void leave(int sig);
//part of code trying to use signal handling
if(signal(SIGINT, leave))
[Code]...
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May 3, 2010
I have written an application which has more than 6 threads.Two threads share a common linked list. Out of two threads one thread reads the linked list node and other thread writes to linked list node.I am using pthread_mutex_lock() API to achieve synchronisation between having access to common linked list. The problem is the first thread which reads the linked list accesses the mutex faster making other thread to starve.
I want both the thread to have an access to mutex. It should not happen that always first thread locks, releases and relocks it. The first thread almost require to access the link list every 5 msec which is causing second thread not to gain the mutex.How should I fix this? For information, I am running this application on PXA270 ARM platform.
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Mar 30, 2010
I am a newbie to Linux. I wanted to know how to explicitly manage memory for applications running on linux. For example, I want to create an application (using C) that has two separate physical address ranges associated with it. How do I assign explicitly those address ranges (the ranges are user defined) to the program?
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Sep 25, 2010
I have installed ubuntu 10.04 using wubi installer..I am dual booting ubuntu with windows 7.I have alloted 8 gb of disk space while installing ubuntu.My first question is how can i know where the installed applications are stored and how much memory they occupy and how much free space is available out of the alloted 8gb.?My second one is now i have to install RAD 7.5 which requires 3.5 gb of free space..How can i expand the disk space without the need of reinstalling ubuntu.
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Aug 17, 2010
configure IfModule mpm_worker_module and mpm_prefork_module by memory Example : I have 1 server ubuntu linux use Apache+PHP - How to configure :
[Code]...
for : 1Gb or 2 Gb - Have math configure <IfModule mpm_worker_module> </IfModule> by memmory?
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Nov 5, 2010
I currently work within an RTOS environment without an MMU and thus have access to the entire memory map of whatever application I'm working on. As is common in the embedded world, different parts of the memory map relate to different peripherals or different types of memory. For our next generation hardware, my company is looking at moving to an MMU-enabled processor and using Linux in some shape or form. Most of us in the dept are familiar with Linux, but we are not Linux gurus by any means. So how to explicitly indicate to Linux that we need certain portions of an application to be stored in NVRam and other portions of the application to NOT be based in NVRam has us confused. None of us have a clear understanding of how user memory is delved out by Linux and how we can influence Linux to use specific portions of the memory map at specific times.
For example in this new application, we expect to have 2 memory chips, both that are DDR3 interfaces. One is a standard DDR3 chip. The other is a non-volatile MRAM with a DDR3 interface so it can be accessed by a DDR3 controller and coexist with conventional DDR3 memory. But because the portion of the memory map that the MRAM will represent will be the only portion of non-volatile memory, we are unclear how we explicitly access MRAM addresses in an MMU-controlled environment. My hail-mary guess was that we would want to somehow tell Linux that we want the MRAM's memory space to be mounted as a RAM Drive and then we access that memory as though it is a file on a HD, except it is much higher speed since it will be at DDR3/MRAM speeds. Is there a better, more straight forward way to do this? Coming from an RTOS world, Linux is going to pose some serious challenges for us, but I think it will be the right move once we are all up to speed and are thinking Linux-centric.
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Sep 22, 2010
I wrote a program that multiplies 2 matrices using multi-threads and another one using multiple processes and shared memory. Both in C.I need to find the total memory usage of these programs. I know of the top command, but when my matrices are relatively small they don't even show up on top because they complete so fast, how can I find the memory usage for these instances?Also, how can I find the total turnaround time of my programs
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Feb 21, 2011
if i attach a shared memory to my process whch part of the address space it will add(like stack, heap, data, code...).
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Nov 19, 2009
I am using Fedora 8 in my PC and i'm trying to create a shared memory (below is the sample program) i'm getting error while creating shared memory. Can anyone pl tell what is the possible cause for this.
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Mar 2, 2010
I have an application consisting of different processes and all these processes are linked to shared libraries. I start the application (spawn all the different processes) as say user1. Now with the application up, if I run a process p1, the process gets activated and works. However, if I start the same process p1 as a different user, say user2, which is completely different from user1 the process complains of
"error while loading shared libraries:...."
I set LD_RUN_PATH both in compile and runtime environment. LD_LIBRARY_PATH is set correctly in both places.
All the above works if I set the absolute path of the required shared libraries in /etc/ld.so.conf file and rebuild the /etc/ld.so.cache
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Aug 16, 2010
Alright, just loaded a fresh copy of OpenSuSE 11.3 x64, went to update manager and let it update, came back and computer was shut down. After booting it back up, I cannot update any software, nor run any commands.
Here is my output:
Code: error while loading shared libraries: libdl.so.2: cannot open shared object file: No such file or directory I've tried searching for this error, some people came back saying to run this:
Code:
But all that happens is this:
Code:
Nor ls work either so I'm stuck and thinking about a reinstall.
I don't understand how this system could be so messed up after a failed update.. Used to trust SuSE, not sure anymore after this incident..
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Nov 9, 2010
Installed Skype but it wont launch. Running the latest Opensuse Gnome. Ive uninstalled it and reinstalled several times but always with the same error. When I try to run it from terminal I get this:
ig@linux-ljqk:~> skype
skype: error while loading shared libraries: libpng12.so.0: cannot open shared object file: No such file or directory
Ive just now uninstalled skype and tried reinstalling it again via yast, but now I get the following error [PK_TMP_DIR|dir:///var/tmp/TmpDir.xftzR0] Repository already exists.
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