Finding Number of Cores in Java

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java availableprocessors
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How can I find the number of cores available to my application from within Java code?

int cores = Runtime.getRuntime().availableProcessors();

If cores is less than one, either your processor is about to die, or your JVM has a serious bug in it, or the universe is about to blow up.

Finding Number of Cores in Java, In this example we shall show you how to get the number of processors with Runtime class. Every Java application has a single instance of  2 CPUs x 2 cores per CPU = 4 total cores You can determine the number of cores available to the Java Virtual Machine by using the static method, availableProcessors from class Runtime. This method is available since Java 1.4.

If you want to get number of physical cores you can run cmd and terminal command and then to parse the output to get info you need.Below is shown function that returns number of physical cores .

private int getNumberOfCPUCores() {
    OSValidator osValidator = new OSValidator();
    String command = "";
    if(osValidator.isMac()){
        command = "sysctl -n machdep.cpu.core_count";
    }else if(osValidator.isUnix()){
        command = "lscpu";
    }else if(osValidator.isWindows()){
        command = "cmd /C WMIC CPU Get /Format:List";
    }
    Process process = null;
    int numberOfCores = 0;
    int sockets = 0;
    try {
        if(osValidator.isMac()){
            String[] cmd = { "/bin/sh", "-c", command};
            process = Runtime.getRuntime().exec(cmd);
        }else{
            process = Runtime.getRuntime().exec(command);
        }
    } catch (IOException e) {
        e.printStackTrace();
    }

    BufferedReader reader = new BufferedReader(
            new InputStreamReader(process.getInputStream()));
    String line;

    try {
        while ((line = reader.readLine()) != null) {
            if(osValidator.isMac()){
                numberOfCores = line.length() > 0 ? Integer.parseInt(line) : 0;
            }else if (osValidator.isUnix()) {
                if (line.contains("Core(s) per socket:")) {
                    numberOfCores = Integer.parseInt(line.split("\\s+")[line.split("\\s+").length - 1]);
                }
                if(line.contains("Socket(s):")){
                    sockets = Integer.parseInt(line.split("\\s+")[line.split("\\s+").length - 1]);
                }
            } else if (osValidator.isWindows()) {
                if (line.contains("NumberOfCores")) {
                    numberOfCores = Integer.parseInt(line.split("=")[1]);
                }
            }
        }
    } catch (IOException e) {
        e.printStackTrace();
    }
    if(osValidator.isUnix()){
        return numberOfCores * sockets;
    }
    return numberOfCores;
}

OSValidator class:

public class OSValidator {

private static String OS = System.getProperty("os.name").toLowerCase();

public static void main(String[] args) {

    System.out.println(OS);

    if (isWindows()) {
        System.out.println("This is Windows");
    } else if (isMac()) {
        System.out.println("This is Mac");
    } else if (isUnix()) {
        System.out.println("This is Unix or Linux");
    } else if (isSolaris()) {
        System.out.println("This is Solaris");
    } else {
        System.out.println("Your OS is not support!!");
    }
}

public static boolean isWindows() {
    return (OS.indexOf("win") >= 0);
}

public static boolean isMac() {
    return (OS.indexOf("mac") >= 0);
}

public static boolean isUnix() {
    return (OS.indexOf("nix") >= 0 || OS.indexOf("nux") >= 0 || OS.indexOf("aix") > 0 );
}

public static boolean isSolaris() {
    return (OS.indexOf("sunos") >= 0);
}
public static String getOS(){
    if (isWindows()) {
        return "win";
    } else if (isMac()) {
        return "osx";
    } else if (isUnix()) {
        return "uni";
    } else if (isSolaris()) {
        return "sol";
    } else {
        return "err";
    }
}

}

Get number of processors with Runtime, java-get-number-of-processors. A code snippet to show you how to get the number of available processors / cores / CPUs in your environment. Multiple users are running java applications on a 60-core compute server (Linux/Ubuntu-based). There are different applications and most of them are not developed in-house. While the sysadmin thinks it is okay for a given user's Java process to use 10 cores at any given moment, she would like them not to use more than 10.

This is an additional way to find out the number of CPU cores (and a lot of other information), but this code requires an additional dependence:

Native Operating System and Hardware Information https://github.com/oshi/oshi

SystemInfo systemInfo = new SystemInfo();
HardwareAbstractionLayer hardwareAbstractionLayer = systemInfo.getHardware();
CentralProcessor centralProcessor = hardwareAbstractionLayer.getProcessor();

Get the number of logical CPUs available for processing:

centralProcessor.getLogicalProcessorCount();

Java – Get number of available processors – Mkyong.com, In order to get the number of available processors in Java, we use the availableProcessors() method. The java.lang.Runtime. Time complexity of the above solution is O(V + E) where V is number of vertices and E is number of edges. Related Concepts : Degeneracy : Degeneracy of a graph is the largest value k such that the graph has a k-core. For example, the above shown graph has a 3-Cores and doesn’t have 4 or higher cores. Therefore, above graph is 3-degenerate.

This works on Windows with Cygwin installed:

System.getenv("NUMBER_OF_PROCESSORS")

Get number of available processors in Java, int cores = Runtime.getRuntime().availableProcessors();. If cores are less than one else processor is about to die, or your JVM has a dangerous  Factorial of 10 = 3628800. In this program, we've used for loop to loop through all numbers between 1 and the given number num (10), and the product of each number till num is stored in a variable factorial. We've used long instead of int to store large results of factorial.

Finding Number of Cores in Java, Finding Number of Cores in Java int cores = Runtime.getRuntime().​availableProcessors(); If cores is less than one, either your processor is  Find out how many cores your processor has. Applies to: Windows 10. Press Ctrl + Shift + Esc to open Task Manager. Select the Performance tab to see how many cores and logical processors your PC has.

Finding Number of Cores in Java, There is no way to get Java to automatically use find out many cores are available and use them all, on AWS ECS using Docker. You have to  The easiest way to see how many cores you have is to open up Task Manager. You can press the CTRL + SHIFT + ESC keyboard shortcut or you can right-click on the Start button and choose it from there. In Windows 7, you can press CTRL + ALT + DELETE and open it from there.

Why is my Java software only using one core, on my multi-core AWS , How do I find the number of cores available for an application from Java code? #​1 building On Windows where Cygwin is installed, you can  Java Program to Count Number of Lines in a File The following program is used to count the total number of lines in the given file. Step 1: Initialize the line count as below int linecount=0; Step 2: Using while loop iterates the contents of the input.txt file.

Comments
  • For pretty much all intents and purpose "core == processor".
  • finding the number of cores the machine has physically is hard using purely Java. Finding the number of cores the Java program can use at startup is easy, using Runtime.getRuntime().availableProcessors(). Due to the ability of all major modern OSes to set CPU affinity (i.e. restrict an application to only a certain number of cores) this is a concern to keep in mind.
  • Logical or physical cores? There's an important difference.
  • Also see: stackoverflow.com/questions/1980832/…
  • This will give you the number of logical threads. e.g. If you have hyper-threading on, this will be double the number of cores.
  • @Peter, yeah, good point. I felt myself King of the Hill when performing this action with my i7 machine! :)
  • @Peter Lawrey: it only gives the number of logical threads actually available to the JVM (at startup I guess). Using CPU affinity the user/OS can restrict the number of "cores" a JVM sees. You can even do it on a running JVM but I'm not too sure how this influence availableProcessors().
  • @PeterLawrey: that seems to be incorrect, the Java documentation for availableProcessors() says "This value may change during a particular invocation of the virtual machine. Applications that are sensitive to the number of available processors should therefore occasionally poll this property and adjust their resource usage appropriately." source
  • @universe blowing up and such : or the machine actually has more than 2,147,483,647 logical threads available ? ;)
  • This is a piece of code that is a good candidate to be OOPed. :)
  • The OSValidator class supports OSX, but the getNumberOfCores completely ignores it. As an aside, blog.opengroup.org/2015/10/02/… so 'Mac' should be in your isUnix() but... For BSD, OSX, no lscpu command exists and your getNumberOfCores will return 0.