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• dynamic memory allocation in C

  - by avanish

  int main() { int p; scanf("%d",&p); fun() { int arr[p]; //isn't this similar to dynamic memory allocation?? } } //if not then what other objective is achieved using malloc and calloc?? //Someone please throw some light :-)

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• Memory allocation problem C/Cpp Windows critical error

  - by Andrew

  Hi! I have a code that need to be "translated" from C to Cpp, and i cant understand, where's a problem. There is the part, where it crashes (windows critical error send/dontSend): nDim = sizeMax*(sizeMax+1)/2; printf("nDim = %d sizeMax = %d\n",nDim,sizeMax); hamilt = (double*)malloc(nDim*sizeof(double)); printf("End hamilt alloc. %d allocated\n",(nDim*sizeof(double))); transProb = (double*)malloc(sizeMax*sizeMax*sizeof(double)); printf("End transProb alloc. %d allocated\n",(sizeMax*sizeMax*sizeof(double))); eValues = (double*)malloc(sizeMax*sizeof(double)); printf("eValues allocated. %d allocated\n",(sizeMax*sizeof(double))); eVectors = (double**)malloc(sizeMax*sizeof(double*)); printf("eVectors allocated. %d allocated\n",(sizeMax*sizeof(double*))); if(eVectors) for(i=0;i<sizeMax;i++) { eVectors[i] = (double*)malloc(sizeMax*sizeof(double)); printf("eVectors %d-th element allocated. %d allocated\n",i,(sizeMax*sizeof(double))); } eValuesPrev = (double*)malloc(sizeMax*sizeof(double)); printf("eValuesPrev allocated. %d allocated\n",(sizeMax*sizeof(double))); eVectorsPrev = (double**)malloc(sizeMax*sizeof(double*)); printf("eVectorsPrev allocated. %d allocated\n",(sizeMax*sizeof(double*))); if(eVectorsPrev) for(i=0;i<sizeMax;i++) { eVectorsPrev[i] = (double*)malloc(sizeMax*sizeof(double)); printf("eVectorsPrev %d-th element allocated. %d allocated\n",i,(sizeMax*sizeof(double))); } Log: nDim = 2485 sizeMax = 70 End hamilt alloc. 19880 allocated End transProb alloc. 39200 allocated eValues allocated. 560 allocated eVectors allocated. 280 allocated So it crashes at the start of the loop of allocation. If i delete this loop it crashes at the next line of allocation. Does it mean that with the numbers like this i have not enough memory?? Thank you.

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• Checking Available Memory allocation in C#

  - by Jepe d Hepe

  i need to create a function in my application to set its available memory usage. What i want to do is when the application is running, and it reaches to the set memory settings, i'll have to switch from saving to the memory to saving to a file to the local drive to avoid application hang. Is this a better way to do? What things to consider when doing this in terms of memory allocation? Hope you understand :) Thanks, Jepe

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• How Byte loading/storing is implemented By the CPU?

  - by AlexDan

  I know that in 32bit machine, cpu read from memory 32bits at a time. since the registers in this case is 32bit in size too, I can understand how this works. What I don't understand is how the cpu implement load instructions of 1 byte. does it load the whole word where the single byte is located to the register, then perform some kind of "byte shifting", or does the cpu can load a single byte, in this case when does the byte masking happen, is it until the byte got loaded in the register, or it happen when byte is send through the data bus ? P.S. The cpu Im using is MIPS, the instructions Im talking about are: lb or lbu

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• Memory allocation in case of static variables

  - by eSKay

  I am always confused about static variables, and the way memory allocation happens for them. For example: int a = 1; const int b = 2; static const int c = 3; int foo(int &arg){ arg++; return arg; } How is the memory allocated for a,b and c? What is the difference (in terms of memory) if I call foo(a), foo(b) and foo(c)?

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• Another dynamic memory allocation bug.

  - by m4design

  I'm trying to allocate memory for a multidimensional array (8 rows, 3 columns). Here's the code for the allocation (I'm sure the error is clear for you) char **ptr = (char **) malloc( sizeof(char) * 8); for (i = 0; i < 3; i++) ptr[i] = (char *) malloc( sizeof(char) * 3); The crash happens when I reference this: ptr[3][0]; Unhandled exception at 0x0135144d in xxxx.exe: 0xC0000005: Access violation writing location 0xabababab. Are there any recommended references/readings for this kind of subject? Thanks.

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• Memory allocation for collections in .NET

  - by Yogendra

  This might be a dupe. I did not find enough information on this. I was discussing memory allocation for collections in .Net. Where is the memory for elements allocated in a collection? List<int> myList = new List<int>(); The variable myList is allocated on stack and it references the List object created on heap. The question is when int elements are added to the myList, where would they be created ? Can anyone point the right direction?

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• Low CPU performance with low usage and clock - Windows 8.1

  - by Daniele

  I recently deleted everything from my PC and reinstalled Windows 8.1 from scratch. When I first booted into Windows everything was extremely slow though the CPU usage was very low (about 1%). After installing some drivers the problem seemed to be solved, I was able to use my PC normally. Today I installed a game and I noticed a strange behavior: the game was playable but the performance worsened more and more in the time. This is the situation BEFORE opening the game (normal): This is AFTER some minutes inside the game (low CPU usage and clock): Some information about my system: PC: Sony Vaio S13 (SVS13A1C5E) OS: Windows 8.1 CPU: Intel Core i7-3520M 2.90GHz GPU(1): Intel HD Graphics 4000 GPU(2): NVIDIA GeForce GT 640M LE I tried searching for new drivers and other solutions but noting worked and I don't know what is the cause. I did not checked the temperatures but the fans are not running fast and the PC does not look overheated. Update: Max CPU Temp: 66°C, Max GPU Temp: 61°C The strange thing is that the GPU load is 99% (GPU-Z) and the fan is almost silent. Update 2: I had troubles with Sony Vaio software, I can't get the FN keys and the STAMINA/SPEED switch to work (it is a physical switch to enable/disable the Nvidia card and change the Power Profile). I'm saying this because I remember that before reinstalling Windows there was an option in the Vaio Control Center (now it is not there anymore) that allowed me to choose from something like "priority to performance (ventilation)" or "priority to silence". The current behavior looks like a "priority to silence", but I can't get the stamina-speed switch to work and so I don't see similar oprions in the Vaio Control Center. I don't know if the problem is related to this.

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• CPU not working on a specific motherboard

  - by Shaman

  I'm making a computer for someone and I met a weird problem. The CPU that I have doesn't work on this motherboard. The CPU is an Intel Pentium D 925 and the motherboard is an ECS G41T-M6, which in theory should work together. The only thing reused is the power source(400W). When I start the computer, the fans start, and that's it. The BIOS doesn't boot. I tried my own power source (600W Corsair) and nothing. Removed the RAM, no warning. In desperation I tried the last thing, swaped my own CPU with this one (Core2Duo E7200). Lo and behold, it worked. Both. The Core2Duo worked on the ECS with the old power source and the RAM that I used in the first place, and the Pentium D worked on my Gigabyte G31M-ES2L. What I discovered was that the Pentium D didn't receive power on the ECS, because I tried running it without the cooler and it remained at room temperature. On a side note, I also removed the HDDs just in case. So, in conclusion, any ideas? I can't return it, and I can still use it to upgrade another PC, but I would really prefer not to buy another CPU if possible.

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• Replaced CPU and black screen but no beep?

  - by luke

  I'm having a bit of trouble with a GIGABYTE GA-MA78G-DS3H (rev. 2.0) motherboard. Recently when trying to clean my AMD Phenom II X 4 CPU, I dropped it and broke some pins. I have now brought a Athlon 64 X2 5400+. However, it does not seem to work. To begin with, I cleared the CMOS via the jumper located near the battery. This was because I had my AMD Phenom II overclocked and did not wish for the same voltage to go to the new CPU. I then tried booting with the monitor plugged into the chipsets VGA but no luck. No signal was sent to the monitor, and the monitor just went into standby. I then tried it off the graphics card but the same happened again. Then I tried to check whether the CPU could executed some BIOS codes by stripping the RAM out and making sure a speaker was plugged in but no beeps could be heard. I replaced the speaker and tried again but no luck. The CPU is brand-new so what is going wrong?

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• Laptop CPU fan not working properly

  - by Smith

  My laptop's CPU fan is suddenly acting very bizarre, and I am at a loss for what to do so I am asking for some help. Specifically, the fan is not even starting to spin until the CPU reaches 60 degrees Celsius (checked through HWmonitor). Once it is on, however, it properly stays on even when the CPU gets back to idle temps around 38 Celsius. Before, the fan was simply starting with the computer and staying on like normal. I've checked this for consistency both by allowing cold boots to ramp up temperature to 60 Celsius (the slow climb also causing the laptop to become unreasonably warm near the heatsink), and also running Prime95 immediately to kickstart the fan (this works every time). The fan seems to be stationary when turning the computer on from either sleep or shutdown. The fan will start at POST very briefly, and then stop completely. I've checked the BIOS for a SmartFan setting but haven't found any. I've opened the case to check for dust or debris and have not found anything (I applied some canned air to the area just in case). The laptop is a Lenovo ThinkPad Edge E430 and the CPU is an Intel Core i5 3210m @ 2.5 GHz. Any advice would really be appreciated.

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• Why does mpstat show different values when I use the interval setting?

  - by Abe

  Here's the output I get when I run mpstat: $mpstat Linux 3.2.0-30-generic (my-laptop-C650) 09/17/2012 _x86_64_ (2 CPU) 05:32:01 PM CPU %usr %nice %sys %iowait %irq %soft %steal %guest %idle 05:32:01 PM all 9.16 0.08 2.69 2.00 0.00 0.04 0.00 0.00 86.02 And here's what I get when I run it with a one-second interval: $mpstat 1 05:31:51 PM CPU %usr %nice %sys %iowait %irq %soft %steal %guest %idle 05:31:52 PM all 1.52 0.00 1.01 0.00 0.00 0.00 0.00 0.00 97.47 05:31:53 PM all 2.04 0.00 1.02 0.00 0.00 0.00 0.00 0.00 96.94 05:31:54 PM all 1.50 0.00 1.50 0.00 0.00 0.00 0.00 0.00 97.00 Why does the first process show the processor as 86% idle, and the second show it as ~97% idle? I've tried this in a bunch of different configurations, and it's not a real difference in CPU usage -- unless mpstat itself is making the difference. Which number should I trust?

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• Windows 7 and laptop overheating

  - by Nikola

  I am using ArchLinux 99% of my working time, and laptop has absolutely no heating problems. But when it comes to using Windows 7, laptop starts heating and one can clearly hear CPU fan working like crazy. I think it has something to do with CPU itself, because on Linux I can simply manipulate with CPU governors (eg. set it to ondemand), but I can't seem to find any similar software to do the same thing as if in Linux. Or, the heating might be caused because of two graphics cards or something? CPU-Z results http://valid.canardpc.com/show_oc.php?id=2310815 Any idea/solution regarding this issue?

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• C++ operator new, object versions, and the allocation sizes

  - by mizubasho

  Hi. I have a question about different versions of an object, their sizes, and allocation. The platform is Solaris 8 (and higher). Let's say we have programs A, B, and C that all link to a shared library D. Some class is defined in the library D, let's call it 'classD', and assume the size is 100 bytes. Now, we want to add a few members to classD for the next version of program A, without affecting existing binaries B or C. The new size will be, say, 120 bytes. We want program A to use the new definition of classD (120 bytes), while programs B and C continue to use the old definition of classD (100 bytes). A, B, and C all use the operator "new" to create instances of D. The question is, when does the operator "new" know the amount of memory to allocate? Compile time or run time? One thing I am afraid of is, programs B and C expect classD to be and alloate 100 bytes whereas the new shared library D requires 120 bytes for classD, and this inconsistency may cause memory corruption in programs B and C if I link them with the new library D. In other words, the area for extra 20 bytes that the new classD require may be allocated to some other variables by program B and C. Is this assumption correct? Thanks for your help.

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• Is memory allocation in linux non-blocking?

  - by Mark

  I am curious to know if the allocating memory using a default new operator is a non-blocking operation. e.g. struct Node { int a,b; }; ... Node foo = new Node(); If multiple threads tried to create a new Node and if one of them was suspended by the OS in the middle of allocation, would it block other threads from making progress? The reason why I ask is because I had a concurrent data structure that created new nodes. I then modified the algorithm to recycle the nodes. The throughput performance of the two algorithms was virtually identical on a 24 core machine. However, I then created an interference program that ran on all the system cores in order to create as much OS pre-emption as possible. The throughput performance of the algorithm that created new nodes decreased by a factor of 5 relative the the algorithm that recycled nodes. I'm curious to know why this would occur. Thanks. *Edit : pointing me to the code for the c++ memory allocator for linux would be helpful as well. I tried looking before posting this question, but had trouble finding it.

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• Memory allocation for a matrix in C

  - by Snogzvwtr

  Why is the following code resulting in Segmentation fault? (I'm trying to create two matrices of the same size, one with static and the other with dynamic allocation) #include <stdio.h> #include <stdlib.h> //Segmentation fault! int main(){ #define X 5000 #define Y 6000 int i; int a[X][Y]; int** b = (int**) malloc(sizeof(int*) * X); for(i=0; i<X; i++){ b[i] = malloc (sizeof(int) * Y); } } Weirdly enough, if I comment out one of the matrix definitions, the code runs fine. Like this: #include <stdio.h> #include <stdlib.h> //No Segmentation fault! int main(){ #define X 5000 #define Y 6000 int i; //int a[X][Y]; int** b = (int**) malloc(sizeof(int*) * X); for(i=0; i<X; i++){ b[i] = malloc (sizeof(int) * Y); } } or #include <stdio.h> #include <stdlib.h> //No Segmentation fault! int main(){ #define X 5000 #define Y 6000 int i; int a[X][Y]; //int** b = (int**) malloc(sizeof(int*) * X); //for(i=0; i<X; i++){ // b[i] = malloc (sizeof(int) * Y); //} } I'm running gcc on Linux on a 32-bit machine.

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• What factors could cause the scalability issue on a 10-core CPU?

  - by JackWM

  I am tuning the performance of parallel Java programs. And want to check the impacts from the Architecture. I'm look into the Intel 10-core CPU, Intel(R) Xeon(R) CPU E7-L8867. I found my program only scales up to 5 cores. What could be the causes? I'm considering the Architecture effects. e.g. memory contention? More specifically, Are the 10 cores symmetric to each other? How many memory controllers does it have?

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• Webalizer causing high CPU load

  - by Tom

  We use webalizer to generate reports on our Apache access logs - it is useful in conjunction with Google Analytics. The problem is that webalizer uses ALOT of CPU when running. If I run top I can see two perl processes with 90% CPU - this slows down the machine and therefore the website for our users. Webalizer is run via a daily cron job (/etc/cron.daily/00webalizer): #! /bin/bash # update access statistics for the web site if [ -s /var/log/httpd/access_log ]; then exec /usr/bin/webalizer -Q fi Does anyone know how to limit how much CPU webalizer can use? For example, would nice help and how would I use it?

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• CPU Usage at 100% with "Hardware Interrupts"

  - by eventualEntropy

  After turning on my desktop one day, I found that my CPU usage was maxed out at 100%, with 99% of that going to hardware "Interrupts". I tried to enable/disable all my devices one by one through the device manager, and found that I could get the CPU usage used by the Interrupts down to 50% by disabling all devices labelled "USB Host Controller" (except the ones for the mouse/keyboard). I found that I also got 10-20% more from disabling "High Definition Audio Controller". Following the tutorial at: http://www.msfn.org/board/topic/140263-how-to-get-the-cause-of-high-cpu-usage-by-dpc-interrupt/ Led me to similar conclusions (that is, that the culprit is mostly "USB Host Controller"): I've tried updating my asus motherboard driver and my video card driver. This is on Windows 7 64 bit. I've spent hours trying to figure this out and I'm running out of ideas short of formatting (which might still not fix it!).

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• How to monitor CPU usage and performance on a Hyper-V server with several VM's

  - by Bjørn

  Hello, I have a server that is running Windows 2008 64 bit Hyper-V, with 8 gigs of RAM and Intel Xeon X3440 @ 2.53 Ghz, which gives me 8 logical cores in the performance monitor on the host system. I have set up three Virtual Machines, all running Windows 2008 32 bit. Build server, running Team City Staging server SQL Server, running SQL Server 2005 I have some troubles with the setup in that the host monitor remains responsive at all times, even though the VM's are seemingly working at 100% cpu and are very sluggish and unresponsive. (I have asked a separate question about that.) So the question here is: What is the best way to monitor how the physical CPU's are actually utilized? The reason I am asking is that I am being told that i cannot reliably use the task manager to monitor CPU usage in a VM.

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• CPU's on Hyper-V host system is just idling, even though VM's are at full throttle

  - by Bjørn

  Hello, I have a server that is running Windows 2008 64 bit Hyper-V, with 8 gigs of RAM and Intel Xeon X3440 @ 2.53 Ghz, which gives me 8 logical cores in the performance monitor on the host system. I have set up three Virtual Machines, all running Windows 2008 32 bit. Build server, running Team City Staging server SQL Server, running SQL Server 2005 These three machines are running very sluggishly, they are at 100% cpu even though the host system is barely using any cpu at all, typically below 10% total. Could anyone please give some tips as to the best setup for CPU allocating? Should I have set each server to have two cores, or should I increase this number above the total number of cores on the host? What is a good number to set on the Virtual Machine Reserve and Virtual Machine Limit? Is 8 gigs of physical RAM insufficient for 3 VM's? Thanks for reading. :)

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• /lib/udev/net.agent causing high CPU usage

  - by Antoine Benkemoun

  We have a number of Soekris boxes running Debian Squeeze. They were installed through an automated process consisting of using deboostrap and copying it unto a Compact Flash card. We use puppet to manage the configuration of all these boxes. Before Debian Squeeze, they were running Voyage Linux which is just a "lighter" version of Debian. Since we have switched, we're seeing the /lib/udev/net.agent process take up an aweful lot of CPU. We have so far been unable to find any clue as to what this really does and why it's taking up some much CPU time. In htop we see the following : We are seeing absolutly no syslog messages related to this process so we're a bit lost... So, I am looking for pointers as to what this process does in general and what could be the potential cause of such CPU usage.

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• Find which php scripts cause high CPU with php-cgi

  - by Oli

  Background: I maintain a server for a client who has half a dozen Wordpress sites on. They all have the W3 Total Cache plugin installed and eAcellerator is installed (might be APC). All the PHP sites run through a single batch of fastcgi php-cgi processes (it's actually php-fpm but I'm not sure if that makes a difference). Problem: php-cgi's CPU usage is quite high. Not terminally high but high enough to raise an eyebrow. The client wants to add more sites in the future and I want to avoid becoming CPU limited if I can help it. Question: Is there any way I can find the scripts or even just requests that are causing the high CPU. I realise I might not be able to do anything with the results but it would give me a chance.

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• Generic socket 940 CPU fan interchangeable with HP part number 411454-001

  - by ConcernedOfTunbridgeWells

  Hi, I'm trying to find a generic CPU fan that will fit the air duct in an XW9300. Note that there are two CPU fan mounting schemes used on this machine. One with two grommets in the motherboard that the CPU fan screws into and one with a plastic collar and base plate. The form factor I'm looking for is the former (see picture below): Two HP part numbers for fans in this form factor are 411454-001 (shown below) and 416055-001. Note that the dimensions are important as the machine has an air duct that fits over the fan. Can anyone tell me the manufacturer and model of an equivalent generic part? Better yet, do you know somewhere (preferrably in the UK) that I can obtain such an item from?

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• Generic socket 940 CPU fan for HP XW9300 interchangeable with HP part number 411454-001

  - by ConcernedOfTunbridgeWells

  Hi, I'm trying to find a generic Socket 940 CPU fan that will fit the air duct in an XW9300. Note that two different CPU fan mounting schemes have been used on this machine. One has two grommets in the motherboard that the CPU fan screws into and the other has a plastic collar and base plate. The form factor I'm looking for is the former (see the picture below). Two HP part numbers for fans in this form factor are 411454-001 (shown below) and 416055-001. Note that the dimensions are important as the machine has an air duct that fits over the fan. Can anyone tell me the manufacturer and model of an equivalent generic part? Better yet, do you know somewhere (preferrably in the UK) from which such an item can be obtained?

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