Add node-example

node-example/README.md

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+# GraalVM demos: Graal.js application
+
+
+This repository contains the code for a demo application for [GraalVM](graalvm.org).
+
+## Prerequisites
+* [GraalVM](http:https://graalvm.org)
+
+## Preparation
+
+Download or clone the repository and navigate into the `node-example` directory:
+
+```
+git clone https://github.com/graalvm/graalvm-demos
+cd graalvm-demos/node-example
+```
+
+Build the application before running. You can manually execute `npm install plotly`, but there's also a `build.sh` script included for your convenience.
+
+Execute:
+```
+bash build.sh
+```
+
+After this export the GraalVM home directory as the `$GRAALVM_HOME`, e.g.:
+
+```
+export GRAALVM_HOME=/home/${USER}/graalvm/graalvm-$GRAALVM_VERSION
+```
+
+## Running the application
+
+To run the application, you need to execute the `taylor.js` file. You can run it with the following command (or run the `run.sh` script):
+
+```
+$GRAALVM_HOME/bin/node taylor.js
+```
+
+Open [localhost:5000](localhost:5000) in your browser to see the output of the example app.
+
+The application tabulates sin(x) function using Taylor series, plots a graph of this function and responses to a client with the image of the graph.
+
+## Benchmarking
+
+You can use `ab` (Apache benchmark) tool for benchmarking while the server is running this way:
+
+```
+ab -n 50 localhost:5000/
+```
+
+This will perform 50 requests to the server and print results of benchmarking.
+
+## Notes about the application
+
+This application uses [Plotly](https://plot.ly) library to plot the graph. Plotly provides API for plotting graphs, and requires username and API key indicated.
+
+To get username and API key, proceed to the [Plotly](https://chart-studio.plot.ly/settings/api#/) site, log in or sign up, go to Settings->API Keys and click on `Regenerate Key` button. Then copy your username and API key and paste them there, on the top of the `taylor.js` file:
+
+```
+const plotly = require('plotly')('username', 'api_key');
+```
+
+This API key can be used 1000 times per 24h.

node-example/build.sh

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+#!/usr/bin/env bash
+
+npm install plotly

node-example/run.sh

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+#!/usr/bin/env bash
+
+$GRAALVM_HOME/bin/node taylor.js

node-example/taylor.js

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+const plotly = require('plotly')('username', 'api_key');
+const http = require('http');
+
+//-----------------------Creating-server------------------------------
+
+const server = http.createServer((req, res) => {
+ outputSinGraph(res);
+});
+
+const PORT = process.env.PORT || 5000;
+
+server.listen(PORT, () => console.log(`Server running on localhost:${PORT}`));
+
+//-----------------------Evaluating-Taylor-series---------------------
+
+const factorial = x => (x < 1) ? 1 : x * factorial(x - 1);
+
+function outputSinGraph(res) {
+ let data = {
+ x : [],
+ y : []
+ };
+
+ let t1 = getNanoSecTime();
+ data = tabulateSin(-Math.PI * 4, Math.PI * 4, 0.1);
+ let time = getNanoSecTime() - t1;
+ console.log(`\nEvaluations took ${time} nanoseconds.\n`);
+
+ function taylorSin(x) {
+ let sum = 0, n = 0, elem = 1, eps = 0.0000001;
+
+ while(Math.abs(elem) > eps) {
+ elem = Math.pow(-1, n) * (Math.pow(x, 2 * n + 1) / factorial(2 * n + 1));
+ sum += elem;
+ n++;
+ }
+ return sum;
+ }
+
+ function tabulateSin(left, right, step) {
+ let x = left;
+ let d = {
+ x : [],
+ y : []
+ };
+ while(x <= right) {
+ let y = taylorSin(x);
+ console.log(`sin(${Math.round(x * 100) / 100}) = ${Math.round(y * 100000) / 100000} --- actual ${Math.round(Math.sin(x) * 100000) / 100000}`);
+ d.x.push(x);
+ d.y.push(y);
+ x += step;
+ }
+ return d;
+ }
+
+ //-----------------------Plotting-graph-------------------------------
+
+ var layout = {
+ title: {
+ text: `Evaluations took ${time} nanoseconds.`,
+ font: {
+ family: 'Courier New, monospace',
+ size: 24
+ },
+ xref: 'paper',
+ x: 0.05,
+ }
+ }
+
+ var trace1 = {
+ x: data.x,
+ y: data.y,
+ type: "scatter"
+ };
+
+ var figure = { 
+ 'data': [trace1],
+ 'layout' : layout
+ };
+
+ var imgOpts = {
+ format: 'png',
+ width: 1000,
+ height: 500
+ };
+
+ plotly.getImage(figure, imgOpts, function (error, imageStream) {
+ if (error) return console.log (error);
+ res.writeHead(200, {'Content-Type': 'image/png'});
+ imageStream.pipe(res);
+ });
+}
+
+//-----------------------Time-measurement-----------------------------
+
+function getNanoSecTime() {
+ var hrTime = process.hrtime();
+ return hrTime[0] * 1000000000 + hrTime[1];
+}