two-product - npm Package Compare versions

Comparing version 1.0.0 to 1.0.1

package.json

		{
		"name": "two-product",
		"version": "1.0.0",
		"version": "1.0.1",
		"description": "Multiplies two floating point numbers together producing a non-overlapping increasing sequence of floats",
		@@ -9,9 +9,9 @@ "main": "two-product.js",
		},
		"dependencies": {
		"dependencies": {},
		"devDependencies": {
		"tape": "^2.12.3",
		"test-float-overlap": "^1.0.3"
		},
		"devDependencies": {
		"tape": "~1.1.0"
		},
		"scripts": {
		"test": "tap test/*.js"
		"test": "tape test/*.js"
		},
		@@ -18,0 +18,0 @@ "repository": {

test/test.js

		"use strict"

		var twoProduct = require("../two-product.js")
		var testOverlap = require("test-float-overlap")

		require("tape")(function(t) {

		t.same(twoProduct(1, 1), [0, 1])
		t.same(twoProduct(Infinity, Infinity), [0,Infinity])
		t.same(twoProduct(Infinity,1), [0,Infinity])
		t.same(twoProduct(Infinity,0), [0,0])
		t.same(twoProduct(Infinity,-Infinity), [0,-Infinity])

		t.end()
		var testValues = [
		0,
		-0,
		-1,
		1,
		Math.pow(2, -52),
		Math.pow(2, -53),
		1.0-Math.pow(2, -53),
		1.0+Math.pow(2, -52),
		Math.pow(2,-500),
		Math.pow(2, 500),
		2,
		0.5,
		3,
		1.5,
		1.2399519200255505e-149 ]
		for(var i=0; i<20; ++i) {
		testValues.push(Math.random())
		testValues.push(Math.random() * Math.pow(2, 1000 * Math.random() - 500))
		}

		for(var j=0; j<testValues.length; ++j) {
		var a = testValues[j]
		t.ok(a*a < Infinity, "check finite: " + a)
		t.same(twoProduct(0, a), [0,0], "multiply by 0")
		t.same(twoProduct(1, a), [0,a], "multiply by 1")
		t.same(twoProduct(-1, a), [0,-a], "multiply by -1")

		for(var k=0; k<testValues.length; ++k) {
		var b = testValues[k]

		var s = twoProduct(a, b)

		t.ok(!testOverlap(s[0], s[1]), "overlapping")
		t.ok(Math.abs(s[0]) <= Math.abs(s[1]), "increasing")
		t.equals(s[1], a*b, "approximation")

		var r = twoProduct(b, a)
		t.same(s, r, "commutativity")
		}
		}

		//Test expansion
		t.same(twoProduct(
		1.0 + Math.pow(2, -52),
		1.0 + Math.pow(2, -52)),
		[Math.pow(2, -104), 1.0 + Math.pow(2, -51)], "test expansion")

		t.end()
		})

two-product.js

		@@ -5,3 +5,3 @@ "use strict"

		var HALF_DOUBLE = (1<<26) + 1
		var SPLITTER = +(Math.pow(2, 26) + 1.0)

		@@ -11,25 +11,25 @@ function twoProduct(a, b, result) {

		var c = HALF_DOUBLE * a
		var c = SPLITTER * a
		var abig = c - a
		var ahi = c - abig
		var alo = a - ahi

		var d = HALF_DOUBLE * b

		var d = SPLITTER * b
		var bbig = d - b
		var bhi = d - bbig
		var blo = b - bhi


		var err1 = x - (ahi * bhi)
		var err2 = err1 - (alo * bhi)
		var err3 = err2 - (ahi * blo)


		var y = alo * blo - err3

		if(result) {
		result[0] = y \|\| 0.0
		result[1] = x \|\| 0.0
		result[0] = y
		result[1] = x
		return result
		}

		return [ y \|\| 0.0, x \|\| 0.0 ]

		return [ y, x ]
		}

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