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https://github.com/rabestro/forward-or-backward
This project aims to show how expensive extra function calls can be when defining a loop boundary.
https://github.com/rabestro/forward-or-backward
backward boundary comparison for-loop forward jmh-benchmarks loops-and-iterations
Last synced: about 2 months ago
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This project aims to show how expensive extra function calls can be when defining a loop boundary.
- Host: GitHub
- URL: https://github.com/rabestro/forward-or-backward
- Owner: rabestro
- License: mit
- Created: 2023-07-30T11:37:39.000Z (over 1 year ago)
- Default Branch: main
- Last Pushed: 2023-07-31T07:09:46.000Z (over 1 year ago)
- Last Synced: 2023-07-31T08:26:46.893Z (over 1 year ago)
- Topics: backward, boundary, comparison, for-loop, forward, jmh-benchmarks, loops-and-iterations
- Language: Java
- Homepage:
- Size: 6.84 KB
- Stars: 0
- Watchers: 1
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- License: LICENSE
Awesome Lists containing this project
README
# Forward or Backward?
This project aims to show how expensive extra function calls can be when defining a loop boundary.
## Description
In this example, we use the number of names in the path as the loop boundary.
We can either start at the beginning of the path and work forward or at the end and work backward.
The results show that working backward in a particular case is six times faster than working forward.
The reason for this is that in the first case, we call the method `Path::getNameCount` on every iteration of the loop, whereas in the last case, we call this function once at the beginning of the circle.
This example shows how important it is to calculate loop boundaries in advance.
## Methods to be benchmarked
```java
public class MyBenchmark {
private static final Path SAMPLE_PATH = Path.of("/home/user/projects/dict/src/main/resources/words.txt");
@Benchmark
public int forwardLoop() {
var count = 0;
// calculate loop boundaries at each iteration
for (
var i = 0;
i < SAMPLE_PATH.getNameCount();
i++
) {
count++;
}
return count;
}
@Benchmark
public int reverseLoop() {
var count = 0;
// calculate loop boundaries once at the very beginning
for (
var i = SAMPLE_PATH.getNameCount();
i > 0;
i--
) {
count++;
}
return count;
}
}
```
## Running the benchmark
To execute the benchmark, access your project folder through the command line and execute the following command.
```shell
mvn clean verify
```
This action will generate the `target` folder within your project, housing the benchmarks Uber-JAR file that you'll utilize.
Next, proceed by running the following command from the same location.
```shell
java -jar target/benchmarks.jar
```
Once all benchmarks conclude, you'll receive the following completion message.
```text
Benchmark Mode Cnt Score Error Units
MyBenchmark.forwardLoop thrpt 25 86563253.402 ± 198686.009 ops/s
MyBenchmark.reverseLoop thrpt 25 517055621.588 ± 2150399.471 ops/s
```
I added a simple graph to represent digital data better.
