sample_get_set.js

'use strict';

let read_and_write_on_same_cache = false;

let N = 10;
let backing_store = [];
let backing_store2 = [];


for(let y=0;y<N;y++)
{
	backing_store.push([]);
	backing_store2.push([]);
	for(let x=0;x<N;x++)
	{
		let r = Math.sqrt( (x-N/2) * (x-N/2) + (y-N/2) * (y-N/2) ); // pixel value depending on distance to center of circle
		backing_store[y].push(r);
		backing_store2[y].push(0);
	}
}
let cache_hit_and_miss = 0;
let cache_misses = 0;
let cache_write_misses = 0;


let Lru = require("./lrucache.js").Lru;
let num_cache_elements = 25;
let element_life_time_miliseconds = 10000;

let cache = new Lru(num_cache_elements, async function(key,callback){	
	cache_misses++;

	let obj = JSON.parse(key);
	let x = obj.x;
	let y = obj.y;

	// simulating slow access to a backing store (will be hidden by async access anyway)
	setTimeout(function(){

		// send the result to a RAM slot in the cache
		callback(backing_store[y][x]);
	},10);

}, element_life_time_miliseconds, async function(key,value,callback){
	cache_write_misses++;	
	
	let obj = JSON.parse(key);
	let x = obj.x;
	let y = obj.y;

	// simulating slow access to a backing store (will be hidden by async access anyway)
	setTimeout(function(){

		// send the result to a RAM slot in the cache
		backing_store[y][x]=value;
		callback();
	},10);

});


let cache2 = new Lru(num_cache_elements, async function(key,callback){	
	cache_misses++;

	let obj = JSON.parse(key);
	let x = obj.x;
	let y = obj.y;

	// simulating slow access to a backing store (will be hidden by async access anyway)
	setTimeout(function(){

		// send the result to a RAM slot in the cache
		callback(backing_store2[y][x]);
	},100);

}, element_life_time_miliseconds, async function(key,value,callback){
	cache_write_misses++;
	
	let obj = JSON.parse(key);
	let x = obj.x;
	let y = obj.y;

	// simulating slow access to a backing store (will be hidden by async access anyway)
	setTimeout(function(){

		// send the result to a RAM slot in the cache
		backing_store2[y][x]=value;
		callback();
	},100);

});

console.log("cache size = "+num_cache_elements+" pixels");
console.log("image size = "+(N*N)+" pixels");
// image softening algorithm
async function benchmark()
{
	let timing = Date.now();
	for(let y=1;y<N-1;y++)
	{
		for(let x=1;x<N-1;x++)
		{
			
			cache_hit_and_miss += 6; // 5 pixels requested for read, 1 for write
			
			
			let softened_pixel = (await cache.getMultipleAwaitable(	JSON.stringify({x:x,y:y}), // center pixel
										JSON.stringify({x:x,y:y-1}), // neighbor up
										JSON.stringify({x:x,y:y+1}), // neighbor down 
										JSON.stringify({x:x-1,y:y}), // neighbor left
										JSON.stringify({x:x+1,y:y})  // neighbor right
			)).reduce((e1,e2)=>{return e1+e2;})/5.0;

			let target = 0;
			if(read_and_write_on_same_cache)
				target = cache;
			else
				target = cache2;

			target.set(JSON.stringify({x:x,y:y}),softened_pixel,async function(val){
				
				if(y==N-2 && x == N-2)
				{
					// write all edited data to backing-store and read all non-read data from backing-store
					target.flush(function(){
						console.log("softened image pixels: ");
						console.log(read_and_write_on_same_cache?backing_store:backing_store2);
						console.log("run-time: "+(Date.now() - timing)+" ms          "+((N-2)*(N-2)*5)+" reads "+((N-2)*(N-2))+" writes");
						console.log("cache read hit ratio="+(100*(cache_hit_and_miss - cache_misses)/cache_hit_and_miss));
						console.log("cache write hit ratio="+(100*(cache_hit_and_miss - cache_write_misses)/cache_hit_and_miss));
					});
				}
			});
	
		}
	}
}

benchmark();