2d:null 2e:["$","title",null,{"children":"Advent of WASM Day 3 | Thomas Ballinger | Observable"}] 33:Tc13,buildPart1Module = () => { const module = new binaryen.Module(); //module.autoDrop(); // automatically pops values off the stack if they aren't last in a block // Just for debugging module.addFunctionImport( 'print', 'env', 'print', [binaryen.i32], binaryen.i32 ); for (let name of ['xMin', 'xMax', 'yMin', 'yMax']) { module.addGlobal(name, binaryen.i32, 1, module.i32.const(0)); } const memSize = Math.floor((1024 * 1024 * 1024) / 65536); module.setMemory(memSize, memSize, 'memory'); module.addFunction( "setBounds", binaryen.createType([ binaryen.i32, binaryen.i32, binaryen.i32, binaryen.i32 ]), binaryen.i32, [], module.block(null, [ ...['xMin', 'xMax', 'yMin', 'yMax'].map((name, i) => module.global.set(name, module.local.get(i, binaryen.i32)) ), //see if memory is enough module.if( module.i32.lt_s( module.memory.size(), module.i32.div_s( module.i32.mul( module.i32.add( module.i32.sub( module.global.get('xMax', binaryen.i32), module.global.get('yMax', binaryen.i32) ), module.i32.const(1) ), module.i32.add( module.i32.sub( module.global.get('yMax', binaryen.i32), module.global.get('yMin', binaryen.i32) ), module.i32.const(1) ) ), module.i32.const(65536) ) ), module.return(module.i32.const(1)) ), module.return(module.i32.const(0)) ]) ); module.addFunctionExport("setBounds", "setBounds"); /** Get location of spot at x and y (local parameters 0 and 1) in linear memory */ const arrayMath = () => { return module.i32.add( // x - xMin module.i32.sub( module.local.get(0, binaryen.i32), module.global.get('xMin', binaryen.i32) ), // (y - yMin) * (xMax - xMin + 1) module.i32.mul( module.i32.sub( module.local.get(1, binaryen.i32), module.global.get('yMin', binaryen.i32) ), module.i32.add( module.i32.sub( module.global.get('xMax', binaryen.i32), module.global.get('xMin', binaryen.i32) ), module.i32.const(1) ) ) ); }; module.addFunction( "recordSpot", binaryen.createType([binaryen.i32, binaryen.i32]), null, [], module.block(null, [ module.i32.store8(0, 0, arrayMath(), module.i32.const(1)) ]) ); module.addFunctionExport("recordSpot", "recordSpot"); module.addFunction( "checkSpot", binaryen.createType([binaryen.i32, binaryen.i32]), binaryen.i32, [], module.block(null, [module.return(module.i32.load8_s(0, 0, arrayMath()))]) ); module.addFunctionExport("checkSpot", "checkSpot"); if (!module.validate()) { throw new Error("validation error"); } return module; }34:T49e,part1Result = { const crossings = [[], []]; for (let i of [0, 1]) { const instance = constructPart1Module(); const result = instance.exports.setBounds( bounds.xMin, bounds.xMax, bounds.yMin, bounds.yMax ); if (result) { throw Error( 'Linear memory of ' + instance.exports.memory.buffer.byteLength + ' bytes not large enough for bounds ' + bounds ); } const recordWire = positions[i]; const checkWire = positions[1 - i]; for (let { x, y } of recordWire) { //console.log('recording spot:', x, y); try { instance.exports.recordSpot(x, y); } catch (e) { console.log(x, y); console.log( 'should be', x - bounds.xMin, y - bounds.yMin, x - bounds.xMin + bounds.width * (y - bounds.yMin) ); throw e; } } let d = 0; for (let { x, y } of checkWire) { //console.log('checking spot:', x, y); const result = instance.exports.checkSpot(x, y); if (result) { crossings[i].push({ x, y, d }); } d++; } } return crossings; }35:[{"id":"38bb32b0a48f7b3557058b93cfd729e88007b5af1a8cf37f9cc522f148b752400bbfa0cd59f694270de82f805dbc4d81ea6ef40e6e45631eb3d518185fe0cd0a","href":"https://static.observableusercontent.com/files/38bb32b0a48f7b3557058b93cfd729e88007b5af1a8cf37f9cc522f148b752400bbfa0cd59f694270de82f805dbc4d81ea6ef40e6e45631eb3d518185fe0cd0a","name":"memusage@2.png","type":"image/png","lastModified":1575751288952.246,"size":239998},{"id":"3746f3d4ee5b6990706f1b472f52be5c8628044486521617374011fe64bb75af17167645a7ef8465a77b9b1b5d601976fda15e9f4ba96600261fccfb3735bf60","href":"https://static.observableusercontent.com/files/3746f3d4ee5b6990706f1b472f52be5c8628044486521617374011fe64bb75af17167645a7ef8465a77b9b1b5d601976fda15e9f4ba96600261fccfb3735bf60","name":"day3input.txt","type":"text/plain","lastModified":1575506901033.829,"size":2939},{"id":"931e6a1bcc7fc15e14122ecc30e78a8a398fe5fdc198f4f439aff9a9a221023e372c438d93b67cb10e5b5f88f8c673395e4578b2c76a3731f753c46b6159210c","href":"https://static.observableusercontent.com/files/931e6a1bcc7fc15e14122ecc30e78a8a398fe5fdc198f4f439aff9a9a221023e372c438d93b67cb10e5b5f88f8c673395e4578b2c76a3731f753c46b6159210c","name":"chromememory.png","type":"image/png","lastModified":1575748313539.56,"size":77575},{"id":"8a535d10eae95899ba2f25e0bba52b2e45aa43f37e6ca982ecb72e84dd0f6b4a5e8baa702cae5810ea0c5c00510d062bc26197b7492250fc1715b76df2979c7c","href":"https://static.observableusercontent.com/files/8a535d10eae95899ba2f25e0bba52b2e45aa43f37e6ca982ecb72e84dd0f6b4a5e8baa702cae5810ea0c5c00510d062bc26197b7492250fc1715b76df2979c7c","name":"firefoxmemory.png","type":"image/png","lastModified":1575748657458.37,"size":61632}] 31:{"id":"1b367d3b14c61214","slug":"advent-of-wasm-day-3","title":"Advent of WASM Day 3","thumbnail":"0ae8205e047bf5712d3f76e772809f1a97fa26f47eb58578eb7c011b674b2298","access_level":"public","create_time":"$D2019-12-05T00:47:37.628Z","update_time":"$D2021-12-22T01:01:34.692Z","view_time":null,"first_public_time":"$D2019-12-06T22:48:18.931Z","fork":false,"stars":2,"starred":false,"owner":{"type":"team","id":"8d59e5c626effee2","login":"ballingt","name":"Thomas Ballinger","avatar_url":"https://avatars-next.observableusercontent.com/fdc16c011489d914c05fa5992a7992413727fc69e4f73671ec38919807f547e7","tier":"starter_2024"},"version":859,"publish_version":859,"role":null,"authored":false,"authors":[{"type":"individual","id":"4c607438c80998ad","login":"ballingt","name":"Thomas Ballinger","avatar_url":"https://avatars-next.observableusercontent.com/fdc16c011489d914c05fa5992a7992413727fc69e4f73671ec38919807f547e7","tier":null}],"members":[{"type":"individual","id":"4c607438c80998ad","login":"ballingt","name":"Thomas Ballinger","avatar_url":"https://avatars-next.observableusercontent.com/fdc16c011489d914c05fa5992a7992413727fc69e4f73671ec38919807f547e7","tier":null,"role":"editor"}],"comments":[],"custom_thumbnail":true,"trashed":false,"lapsed":null,"subscribed":null,"forks":0,"collection":{"id":"320466a8967f257d","slug":"advent-of-wasm","title":"Advent of WASM","owner":{"id":"8d59e5c626effee2","login":"ballingt","name":"Thomas Ballinger"}},"type":"notebook","body":{"title":"Advent of WASM Day 3","cells":[{"id":0,"value":"md`# Advent of WASM Day 3\n\n[Advent of Code](https://adventofcode.com/2019) in WebAssembly!`","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":5,"value":"md`# [Part 1](https://adventofcode.com/2019/day/3)\n\nSome input parsing, processing, then comparison today. We'll start in JavaScript...`","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":8,"value":"wires = (await FileAttachment(\"day3input.txt\").text())\n .trim()\n .split('\\n')\n .map(line =>\n line\n .split(',')\n .map(x => ({ direction: x[0], magnitude: parseInt(x.slice(1)) }))\n )","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":10,"value":"md`There are three ways it occurs to me to represent these wires:\n#### as lists of segments\n\\`\\`\\`\n[R2, D3] -> [\n [{x:0, y:0}, {x:2, y:0}],\n [{x: 2, y:0}, {x:2, y:-3}]\n]\n\\`\\`\\`\n\n#### as a sparse arrays or maps of positions\n\\`\\`\\`\n[R2, D3] -> [\n {x:0, y:0},\n {x: 0, y:1}, \n {x:2, y:0}, \n {x:2, y:-1},\n {x:2, y:-2},\n {x:2, y:-3}]\n\\`\\`\\`\n\n#### as dense array of positions\n\n\\`\\`\\`\n[R2, D3] -> {\n bounds: {xMin: 0, w:3, yMin: -3, h: 4},\n data:[\n [1, 1, 1], \n [0, 0, 1],\n [0, 0, 1],\n [0, 0, 1]]\n}\\`\\`\\`\n\nThe last best lends itself to visualization, and seems most straightforward if we can get away with it. It's also by far the least efficient. Let's find out how big that array would be.`","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":13,"value":"delta = ({ direction, magnitude }) => {\n switch (direction) {\n case 'L':\n return { dx: -magnitude, dy: 0 };\n case 'R':\n return { dx: magnitude, dy: 0 };\n case 'U':\n return { dx: 0, dy: magnitude };\n case 'D':\n return { dx: 0, dy: -magnitude };\n default:\n throw Error(\"Bad direction: \" + direction);\n }\n}","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":16,"value":"turnPositions = [].concat.apply(\n [],\n wires.map(\n wire =>\n wire.reduce(\n ({ curPos: { x, y }, positions }, { direction, magnitude }) => {\n const { dx, dy } = delta({ direction, magnitude });\n x = x + dx;\n y = y + dy;\n positions.push({ x, y });\n return { curPos: { x, y }, positions };\n },\n { curPos: { x: 0, y: 0 }, positions: [] }\n ).positions\n )\n)","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":588,"value":"getBounds = arr => {\n let xMin = Infinity;\n let xMax = -Infinity;\n let yMin = Infinity;\n let yMax = -Infinity;\n for (const v of arr) {\n if (v.x < xMin) xMin = v.x;\n if (v.x > xMax) xMax = v.x;\n if (v.y < yMin) yMin = v.y;\n if (v.y > yMax) yMax = v.y;\n }\n return {\n xMin,\n xMax,\n yMin,\n yMax,\n width: xMax - xMin + 1,\n height: yMax - yMin + 1,\n size: (xMax - xMin + 1) * (yMax - yMin + 1)\n };\n}","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":580,"value":"bounds = getBounds(turnPositions)","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":18,"value":"md`I want to store up to 2 bits of information here: the presence or absence of wire 1 and wire 2. But it's probably easiest to use full 32-bit integers. So ${\n bounds.width\n} by ${bounds.height} gives us ${bounds.width *\n bounds.height} pixels to check for intersections at, which at 32-bits a piece would cost ${Math.round(\n (bounds.size * 4) / 1024 / 1024\n)} MB. I don't think we can justify that. It also wouldn't render real well on a canvas. So storage and visualization and computational complexity, we should to think of these as lines not pixels.\n\nThe line segments representation isn't bad:`","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":21,"value":"segments = wires.map(\n wire =>\n wire.reduce(\n ({ curPos: { x, y }, positions }, { direction, magnitude }) => {\n const { dx, dy } = delta({ direction, magnitude });\n\n const newX = x + dx;\n const newY = y + dy;\n positions.push({\n xMin: Math.min(x, newX),\n xMax: Math.max(x, newX),\n yMin: Math.min(y, newY),\n yMax: Math.max(y, newY)\n });\n return { curPos: { x: newX, y: newY }, positions };\n },\n { curPos: { x: 0, y: 0 }, positions: [] }\n ).positions\n)","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":24,"value":"md`This is Observable, we'd better visualize these real quick`","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":29,"value":"viewof zoom = html``","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":31,"value":"wiresChart = html`\n

\n \n ${segments[0].map(seg => wireDiv(seg, 0))}\n ${segments[1].map(seg => wireDiv(seg, 1))}\n

\n`","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":26,"value":"wireDiv = ({ xMin, xMax, yMin, yMax }, which) => {\n const text = xMin === xMax ? `x = ${xMax}` : `y = ${yMax}`;\n xMin *= zoom;\n xMax *= zoom;\n yMin *= zoom;\n yMax *= zoom;\n const left = `${((xMin - bounds.xMin) / bounds.width) * 100}%`;\n const bottom = `${((yMin - bounds.yMin) / bounds.height) * 100}%`;\n const width = `${((xMax - xMin) / bounds.width) * 100}%`;\n const height = `${((yMax - yMin) / bounds.height) * 100}%`;\n return html`\n \n \n`;\n}","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":33,"value":"md`Based on this visualization our answer might be x = 860, y = 0. But where's our WebAssembly?`","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":43,"value":"md`Let's try that other representation, two lists of {x,y} positions.`","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":57,"value":"positions = wires.map(\n wire =>\n wire.reduce(\n ({ curPos: { x, y, d }, positions }, { direction, magnitude }) => {\n const { dx, dy } = delta({ direction, magnitude });\n\n const destX = x + dx;\n const destY = y + dy;\n while (x !== destX || y !== destY) {\n d++;\n x = x + Math.sign(dx);\n y = y + Math.sign(dy);\n positions.push({ x, y, d });\n }\n\n return { curPos: { x, y, d }, positions };\n },\n { curPos: { x: 0, y: 0, d: 0 }, positions: [{ x: 0, y: 0, d: 0 }] }\n ).positions\n)","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":78,"value":"md`With wires represented as a list of positions, we could walk along either one checking for inclusion in the other. Is this specific enough a task for WebAssembly yet?\n\nIf we encode this data into linear memory, our WebAssembly module could walk along it, but to quickly check for inclusion of points in the other list it seems like we'd need a fancy data structure. I guess we could sort the points and write the binary search in WebAssembly? Binary search isn't the most fun thing in the world to write out in assembly... but I'd rather write that than a hash table implementation.\n\nI feel like this always happens to me in C: my mind is so stuck on maps / associative arrays / dictionaries / objects that I can't think of solutions that don't involve writing a hash map first.`","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":79,"value":"md`What about the naive array implementation we dismissed up above as too large: we need an array with ${\n bounds.size\n} elements to represent every potential point, but then there's no hashing to do. If each point were represented by only one byte intead of four, that's ${Math.ceil(\n bounds.size / 1024 / 1024\n)} MB. Maybe WebAssembly memory arrays can be that big?\n\nReading a bit, it sounds like the limit on how much space we get is decided by what the browser thinks will keep pages responsive for the user. So let's see if we can get away with a few hundred megs.`","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":92,"value":"md`I'll grab our module building code from yesterday and write some code. It doesn't really matter what the code does, I just want to know if we can instantiate a module with this much linear memory.`","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":88,"value":"import { codeWithModuleBoilerplate } from '@ballingt/advent-of-wasm-day-2'","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":91,"value":"testCode = {\n // prettier-ignore\n return [\n 0x00, // there are no local variables\n\n 0x20, 0x00, // load passed-in parameter \"location\"\n 0x28, 0x02, 0x00, // load the 32-bit integer at this location\n 0x0B // END opcode\n ]\n}","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":86,"value":"async function buildModule(numBytes) {\n const pageSize = 65536;\n const memory = new WebAssembly.Memory({\n initial: Math.ceil(numBytes / pageSize)\n });\n const spots = new Int8Array(memory.buffer);\n const importObj = {\n e: {\n m: memory\n }\n };\n\n const linear = codeWithModuleBoilerplate(testCode);\n const linearBuffer = new Uint8Array(linear);\n const module = await WebAssembly.compile(linearBuffer);\n const instance = await WebAssembly.instantiate(module, importObj);\n return spots;\n}","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":75,"value":"buildModule(1)","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":177,"value":"bigMemory = buildModule(1024 * 1024 * 1024)","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":194,"value":"md`On Firefox I can get up to 1GiB but get cut off at 1GiB + 1 page.\n\n

\n\nOn Chrome I get an error at 2 GiB but can go up to one page less.\n\n

\n\nThere are docs for the api [here](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/WebAssembly/Memory) but no info on limits.\n\nEither one of these is enough for my dense array, I only need 370 Megs!\n`","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":181,"value":"md`Fortunately just allocating this memory doesn't cause memory useage to increase yet. It's not until this array is filled up, by running code like this for example,\n\\`\\`\\`javascript\nbigMemoryWithData = {\n for (let i = 0; i < bigMemory.length; i++) {\n bigMemory[i] = 1;\n }\n return bigMemory;\n}\n\\`\\`\\`\nthat the browser's memory usage spikes:\n\n

\n\nFurthermore, I think this is happening on a page-by-page (real memory page, not webassembly page) basis, so using using a dense array to represent these paths ends up getting some of the efficiency of a sparse representation on a page-by-page basis so long as we have 4kb wide runs of empty locations in our array. We're using the virtual memory system's sparse array do the compression!`","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":261,"value":"md`# Back to WebAssembly\n\nFor days [1] and [2], and in the example code above, we wrote WebAssembly by hand. It's tempting to start writing helper functions for encoding sections and vectors, and to start using enums for the bytes, much like Colin Eberhardt's [WebAssembly Compiler](https://blog.scottlogic.com/2019/05/17/webassembly-compiler.html) TypeScript code does. Instead, I'm going to move to [Binaryen](https://github.com/WebAssembly/binaryen), a compiler toolchain for WebAssembly.`","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":263,"value":"binaryen = require(\"binaryen@100\")","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":666,"value":"md`Writing code with Binaryen looks sort of like using LLVM bindings to contruct LLVM intermediate code in memory.`","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":818,"value":"module = new binaryen.Module()","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":266,"value":"exampleModule = {\n const module = new binaryen.Module();\n //module.autoDrop(); // automatically pops values off the stack if they aren't last in a block\n module.addFunctionImport('print', 'env', 'print', [binaryen.i32], null);\n\n module.addFunction(\n \"main\",\n [],\n binaryen.i32,\n [],\n module.block(null, [module.return(module.i32.const(42))])\n );\n module.addFunctionExport(\"main\", \"main\");\n\n if (!module.validate()) {\n throw new Error(\"validation error\");\n }\n\n return module;\n}","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":278,"value":"md`This Binaryen module object can output a binary, or another alternative format we're skipping over for now, WebAssembly Text format (WAT):`","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":270,"value":"exampleModule.emitText()","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":670,"value":"md`As when we wrote our module by hand, we build a WebAssembly.Module with the data, provide imports to our module, and run it.`","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":273,"value":"runWASM = module => {\n const importObj = {\n env: {\n print: x => {\n console.log(x);\n }\n }\n };\n\n var wasmData = module.emitBinary();\n var compiled = new WebAssembly.Module(wasmData);\n var instance = new WebAssembly.Instance(compiled, importObj);\n return instance.exports.main();\n}","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":275,"value":"runWASM(exampleModule)","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":285,"value":"md`# Part 1 for real now`","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":232,"value":"md`Let's get to it then: we need to\n* allocate an array\n* write a WebAssembly module function for data entry: entering all the points of the first wire and storing them in our \"one big array\" internal data structure\n* write a WebAssembly module function for checking points \n\n~~~cpp\nint setBounds(xMin: int, xMax: int, yMin: int, yMax: int)\n// returns 1 if module has been allocated enough memory to store points in these bounds\n\nvoid recordSpot(x: int, y: int)\n\nint checkSpot(x: int, y: int)\n// returns length of wire if touching, otherwise 0\n~~~\n\nFor part 2 (I peeked, turns out the visualization gave us the right answer to part 1) we'll also want to know the distance along each wire that each wire intersection happens. So we'll keep a counter as we go and after storing wire 1 and walking along wire 2, we'll store wire 2 and walk along wire 1.`","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":286,"value":"$33","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":298,"value":"constructPart1Module = () => {\n const importObj = {\n env: {\n print: x => {\n console.log(x);\n return x;\n }\n }\n };\n\n var module = buildPart1Module();\n var wasmData = module.emitBinary();\n var compiled = new WebAssembly.Module(wasmData);\n return new WebAssembly.Instance(compiled, importObj);\n}","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":310,"value":"$34","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":715,"value":"md`That's enough for today. Let's sort through these wire crossings and be done with it.`","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":716,"value":"crossingLocations = {\n const crossingLocations = {};\n const key = obj => obj.x + \":\" + obj.y;\n for (const crossingSet of part1Result) {\n for (const crossing of crossingSet) {\n if (!crossingLocations[key(crossing)]) {\n crossingLocations[key(crossing)] = { ...crossing };\n crossingLocations[key(crossing)].manhattan =\n Math.abs(crossing.x) + Math.abs(crossing.y);\n } else {\n crossingLocations[key(crossing)].d1 =\n crossingLocations[key(crossing)].d;\n crossingLocations[key(crossing)].d2 = crossing.d;\n crossingLocations[key(crossing)].d =\n crossingLocations[key(crossing)].d + crossing.d;\n }\n }\n }\n return Object.values(crossingLocations);\n}","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":724,"value":"closestToOrigin = {\n const crossings = crossingLocations.slice();\n crossings.sort((a, b) => a.manhattan - b.manhattan);\n // ignore first item, that's the crossing point at the origin\n return crossings[1].manhattan;\n}","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":737,"value":"md`# Part 2\nMinimum combined distance from the center\n`","pinned":false,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":736,"value":"fewestCombinedSteps = {\n const crossings = crossingLocations.slice();\n crossings.sort((a, b) => a.d - b.d);\n // ignore first item, that's the crossing point at the origin\n return crossings[1].d;\n}","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"},{"id":854,"value":"data = segments","pinned":true,"hidden":false,"mode":"ojs","author":"$undefined","summary":"$undefined","output":"$undefined","database":"$undefined"}],"files":"$W35","stdlib":"1","titling":"auto"}} 32:"$31:body"