Guide To Learn
So far, we’ve used this_image and num_images to instruct each image to tell us who it is and how many total images there are. This is useful information, but we still haven’t done anything with it yet. How can we use this information to split the weather buoy data between images? Recall from listing 7.1 that we define the list of […]
To tell the images what to work on, we first need to know more about the images themselves, specifically how many there are and who they are. Fortran provides the functions this_image and num_images to do exactly this. Here’s how we write the image number and total number of images to screen: Let’s store this into a file, hello_images.f 90, compile […]
When writing a parallel Fortran program, you don’t have to worry about whether you’re writing a multithreaded concurrent application that’s meant to run on a single core, a shared-memory multicore application, or a distributed memory application. The code that you write is independent of the underlying architecture. Fortran introduces the concept of image, which identifies parallel […]
What is the smallest change required to convert Fortran into a robust and efficient parallel language? Our answer is a simple syntactic extension. It looks and feels like Fortran and requires Fortran programmers to learn only a few new rules. –John Reid, Coarrays in the next Fortran Standard You need to grasp two concepts to […]
Before we devise our parallelization strategy, let’s first go over the serial program, as shown in the following listing, so we understand how each step works. Listing 7.1 Serial implementation of the weather buoy processing program ❶ Helper functions for working with arrays ❷ Subroutine to read the buoy CSV data ❸ Dynamic arrays for timestamps and wind […]
Let’s set some simple objectives for our data analysis exercise. This should be challenging enough to require data decomposition and communication in parallel mode, but simple enough to not get bogged down in the details of math or statistics. To that end, I’d like to know To find the answers, we’ll need our program to […]
The complete source code for the weather buoy exercise is available on GitHub at https://github.com/modern-fortran/weather-buoys. If you use git, clone it directly from the command line: Otherwise, you can download it as a zip file from http://mng.bz/aRVo. The CSV data files are located in the weather-buoys/data directory. I encourage you to explore the data files from your […]
The dataset that we’ll use in this exercise consists of hourly measurements of several weather, ocean, and wave parameters, recorded by buoys managed by the NOAA National Data Buoy Center (NDBC). One such buoy is shown in figure 7.2. Figure 7.2 A weather and wave buoy operated by the NDBC. Instruments that measure wind, temperature, […]
For a gentle entry into parallel programming, we’ll process and analyze a real-world weather buoy dataset. This is a miniature example of the big data challenge: how to process a large amount of data that may be too big to fit into memory, or may take too long to process sequentially. The crux of the […]
The way the processor industry is going, is to add more and more cores, but nobody knows how to program those things. I mean, two, yeah; four, not really; eight, forget it. –Steve Jobs (2008) You may be asking, Why write parallel programs? It seems like an unnecessary complication. In general, you’ll want to write […]