If you’re looking to make it as a Senior Software Engineer, you’re probably aware of how important multithreading and concurrency concepts can be. With the rapid rise of multi-core machines, engineers who are able to skillfully navigate their complexity are the most highly desired candidates by most tech companies today.
These concepts can seem more intimidating than they actually are. We want to debunk the fears around multithreading and introduce you to the basics. We will introduce you to multithreading and concurrency practices in Java, C++, and Go.
Here’s what will be covered today:
- What is multithreading?
- Why use multithreading?
- Basic concepts in multithreading
- Issues involved with multiple threads
- How to avoid issues with multiple threads
- What to learn next
Become a top candidate and master concurrency.
Become proficient in concurrency with your language of choice. All through hands-on practice and real-world applications.
Concurrency for Senior Engineers
What is multithreading?
Multithreading is a technique that allows for concurrent (simultaneous) execution of two or more parts of a program for maximum utilization of a CPU. As a really basic example, multithreading allows you to write code in one program and listen to music in another. Programs are made up of processes and threads. You can think of it like this:
A program is an executable file like chrome.exe
A process is an executing instance of a program. When you double click on the Google Chrome icon on your computer, you start a process which will run the Google Chrome program.
Thread is the smallest executable unit of a process. A process can have multiple threads with one main thread. In the example, a single thread could be displaying the current tab you’re in, and a different thread could be another tab.
Example of multithreading
Think about a single processor that is running your IDE. Say you edit one of your code files and click save. When you click save, it will initiate a workflow which will cause bytes to be written out to the underlying physical disk. However, IO is an expensive operation, and the CPU will be idle while bytes are being written out to the disk.
While IO takes place, the idle CPU could work on something useful and here is where threads come in - the IO thread is switched out and the UI thread gets scheduled on the CPU so that if you click elsewhere on the screen, your IDE is still responsive and does not appear hung or frozen.
Threads can give the illusion of multitasking even though at any given point in time the CPU is executing only one thread. Each thread gets a slice of time on the CPU and then gets switched out either.
It initiates a task, which requires waiting and not utilizing the CPU or it completes its time slot on the CPU. There are many more nuances and intricacies on how thread scheduling works but this forms the basis of it.
With advances in hardware technology, it is now common to have multi-core machines. Applications can take advantage of these and have a dedicated CPU run each thread.
Why use multithreading?
With the introduction of multiple cores, multithreading has become extremely important in terms of the efficiency of your application. With multiple threads and a single core, your application would have to transition back and forth to give the illusion of multitasking.
With multiple cores, your application can take advantage of the underlying hardware to run individual threads through a dedicated core, thus making your application more responsive and efficient. Multithreading basically allows you to take full advantage of your CPU and the multiple cores, so you don’t have untapped processing power with idle cores.
Developers should make use of multithreading for a few reasons:
- Higher throughput
- Responsive applications that give the illusion of multitasking.
- Efficient utilization of resources. Thread creation is light-weight in comparison to spawning a brand new process and for web servers that use threads instead of creating a new process when fielding web requests, consume far fewer resources.
Note that you can’t continually add threads and expect your application to run faster. More threads means more problems, and you must carefully and thoughtfully design how they will work together. It may even be in some cases that you want to avoid multithreading altogether, especially when your application performs a lot of sequential operations.
An understanding of how threading works and knowledge of concurrent programming principles will exhibit maturity and technical depth of a developer. It’s also an important differentiator in landing a more senior job at a company.
