Merge pull request #66 from conveyal/single-propagation

feat(propagation): Generate spectrogram data and surfaces simultaneou…

example.js

@@ -136,9 +136,9 @@ map.on('click', async function (e) {
 
         console.time('generating surface')
         console.time('generating both surfaces')
-        await bc.generateSurface()
+        await bc.generateSurface('jobs')
         console.timeEnd('generating surface')
-        await bc2.generateSurface()
+        await bc2.generateSurface('jobs')
         console.timeEnd('generating both surfaces')
 
         if (surfaceLayer) map.removeLayer(surfaceLayer)

lib/get-surface.js

@@ -2,19 +2,37 @@ import dbg from 'debug'
 import propagate from './propagation'
 const debug = dbg('browsochrones:get-surface')
 
+const MAX_TRIP_LENGTH = 120 // minutes
+
 /**
  * Get a travel time surface and accessibility results for a particular origin.
  * Pass in references to the query (the JS object stored in query.json), the stopTreeCache, the origin file, the
  * x and y origin point relative to the query, what parameter you want (BEST_CASE, WORST_CASE or MEDIAN),
- * and a cutoff for accessibility calculations. Returns a travel time/accessibility surface which can be used by isochoroneTile and accessibilityForCutoff
+ * and a cutoff for accessibility calculations. Sets the current surface within the Browsochrones instance,
+ * and returns data used to draw a spectrogram.
+ * This is basically just an array of curves like so:
+ * For each iteration you will have an array of
+ *  [opportunities reachable in 1 minute,
+ *   marginal opportunities reachable in 2 minutes,
+ *   ...
+ *   marginal opportunities reachable in 120 minutes]
+ *
+ * This does mean that changing the grid requires recomputing the surface even though that's not technically
+ * required. It is assumed this is a relatively rare occurence and it's worth the extra work there to
+ * avoid doing propagation twice, once for getting the surface and once for the spectrogram data.
+ * It's also better than having duplicate code to avoid computing a surface sometimes. We could add a
+ * switch to this function to select what is generated but that may even be more complexity than is needed.
  */
-export default function getSurface ({origin, query, stopTreeCache, which}) {
-  debug('generating surface')
+export default function getSurfaceAndSpectrogramData ({origin, query, stopTreeCache, grid, which}) {
+  debug('generating surface and spectrogram data')
   const surface = new Uint8Array(query.width * query.height)
   const waitTimes = new Uint8Array(query.width * query.height)
   const inVehicleTravelTimes = new Uint8Array(query.width * query.height)
   const walkTimes = new Uint8Array(query.width * query.height)
 
+  const spectrogramData = []
+  for (let i = 0; i < origin.nMinutes; i++) spectrogramData.push(new Uint32Array(MAX_TRIP_LENGTH))
+
   const transitOffset = getTransitOffset(origin.data[0])
 
   // how many departure minutes are there. skip number of stops
@@ -24,20 +42,38 @@ export default function getSurface ({origin, query, stopTreeCache, which}) {
     query,
     stopTreeCache,
     origin,
-    callback: ({
+    callback ({
       travelTimesForDest,
       walkTimesForDest,
       inVehicleTravelTimesForDest,
       waitTimesForDest,
       x,
       y
-    }) => {
+    }) {
+      // handle surface
       const pixelIdx = y * query.width + x
       // compute and set value for pixel
       surface[pixelIdx] = computePixelValue(which, travelTimesForDest)
       waitTimes[pixelIdx] = computePixelValue(which, waitTimesForDest)
       walkTimes[pixelIdx] = computePixelValue(which, walkTimesForDest)
       inVehicleTravelTimes[pixelIdx] = computePixelValue(which, inVehicleTravelTimesForDest)
+
+      // handle spectrogram data
+      const gridx = x + query.west - grid.west
+      const gridy = y + query.north - grid.north
+
+      if (grid.contains(gridx, gridy)) {
+        const val = grid.data[gridy * grid.width + gridx]
+
+        for (let i = 0; i < travelTimesForDest.length; i++) {
+          const time = travelTimesForDest[i]
+          if (time !== 255 && time < MAX_TRIP_LENGTH) {
+            // time - 1 so areas reachable in 1 minute will be included in output[i][0]
+            // TODO audit all the places we're flooring things
+            spectrogramData[i][time - 1] += val
+          }
+        }
+      }
     }
   })
 
@@ -49,6 +85,7 @@ export default function getSurface ({origin, query, stopTreeCache, which}) {
     walkTimes,
     inVehicleTravelTimes,
     query,
+    spectrogramData,
     nMinutes // TODO already present in query
   }
 }

lib/get-transitive-data.js

@@ -28,10 +28,11 @@ export default function getTransitiveData ({ origin, query, stopTreeCache, netwo
 
   // from can be left null and it will be inferred from the destination
   const fromCoord = from != null ? ll(from) : {}
+  const fromName = from != null ? from.name : null
 
   output.places.push({
     place_id: 'from',
-    place_name: from.name, // TODO do this with icons, avoid English works (or Portuguese words, for that matter)
+    place_name: fromName, // todo do this with icons, avoid English works (or Portuguese words, for that matter)
     place_lat: fromCoord.lat || pixelToLat(query.north + origin.y, query.zoom),
     place_lon: fromCoord.lon || pixelToLon(query.west + origin.x, query.zoom)
   })

lib/index.js

@@ -1,3 +1,4 @@
+import assert from 'assert'
 import WebWorkerPromiseInterface from 'web-worker-promise-interface'
 
 import {create as createGridFunc} from './grid'
@@ -7,10 +8,6 @@ import workerHandlers from './worker-handlers'
 const imageHeight = 256
 const imageWidth = 256
 
-function assert (e, msg) {
-  if (!e) throw new Error(msg)
-}
-
 export default class Browsochrones extends WebWorkerPromiseInterface {
   originLoaded = false
   query = false
@@ -77,6 +74,7 @@ export default class Browsochrones extends WebWorkerPromiseInterface {
   }
 
   async getAccessibilityForGrid (grid, cutoff = 60) {
+    assert(grid, 'A grid is required to get accessibility.')
     assert(this.isLoaded(), 'Accessibility cannot be computed before generating a surface.')
 
     return this.work({
@@ -87,18 +85,9 @@ export default class Browsochrones extends WebWorkerPromiseInterface {
     })
   }
 
-  async getSpectrogramData (grid) {
-    assert(this.isLoaded(), 'Accessibility cannot be computed before generating a surface.')
-
-    return this.work({
-      command: 'getSpectrogramData',
-      message: {
-        grid
-      }
-    })
-  }
-
   async generateDestinationData ({ from, to }) {
+    assert(from, '`from` is required to generate destination data.')
+    assert(to, '`to` is required to generate destination data.')
     assert(this.isLoaded(), 'Transitive data cannot be generated if Browsochrones is not fully loaded.')
 
     return this.work({
@@ -128,24 +117,30 @@ export default class Browsochrones extends WebWorkerPromiseInterface {
     })
   }
 
-  async generateSurface (which = 'MEDIAN') {
+  async generateSurface (grid, which = 'MEDIAN') {
+    assert(grid, 'A grid is required to generate a surface.')
     assert(this.isLoaded(), 'Surface cannot be generated if Browsochrones is not fully loaded.')
 
     return this.work({
       command: 'generateSurface',
       message: {
+        grid,
         which
       }
     }).then((message) => {
       this.surfaceLoaded = true
+      return message
     })
   }
 
   latLonToOriginPoint ({lat, lon, lng}) {
+    assert(lat, 'A latitude is required to generate an origin point.')
+    assert(lon || lng, 'A longitude is required to generate an origin point.')
     assert(this.query, 'Cannot convert lat/lon without query.')
+
     const {north, west, zoom} = this.query
-    const x = latToPixel(lat, zoom)
-    const y = lonToPixel(lon || lng, zoom)
+    const x = lonToPixel(lon || lng, zoom)
+    const y = latToPixel(lat, zoom)
     const ret = {
       // TODO should these be rounded instead of floored?
       x: (x - west) | 0,

lib/propagation.js

@@ -13,7 +13,6 @@
  *   y: Y coordinate of grid for this destination
  */
 
-import fill from 'lodash.fill'
 import {getNonTransitTime, ITERATION_WIDTH} from './origin'
 
 export default function propagate ({ query, stopTreeCache, origin, callback }) {
@@ -33,10 +32,10 @@ export default function propagate ({ query, stopTreeCache, origin, callback }) {
       const nonTransitTime = getNonTransitTime(origin, {x, y})
 
       // fill with unreachable, or the walk distance
-      fill(travelTimesForDest, nonTransitTime)
-      fill(waitTimesForDest, 255)
-      fill(inVehicleTravelTimesForDest, 255)
-      fill(walkTimesForDest, nonTransitTime) // when the origin is within walking distance and
+      travelTimesForDest.fill(nonTransitTime)
+      waitTimesForDest.fill(255)
+      inVehicleTravelTimesForDest.fill(255)
+      walkTimesForDest.fill(nonTransitTime) // when the origin is within walking distance and
         // walking is the fastest way to reach the destination, _everything_ is walk time
 
       for (let stopIdx = 0; stopIdx < nStops; stopIdx++) {

lib/worker-handlers.js

@@ -9,7 +9,6 @@ import {create as createGrid} from './grid'
 import * as mercator from './mercator'
 import {create as createOrigin} from './origin'
 import {create as createStopTreeCache} from './stop-tree-cache'
-import getSpectrogramData from './get-spectrogram-data'
 
 module.exports = createHandler({
   putGrid (ctx, message) {
@@ -46,13 +45,17 @@ module.exports = createHandler({
     ctx.transitiveNetwork = message.network
   },
   generateSurface (ctx, message) {
-    ctx.surface = getSurface({
-      cutoff: message.cutoff,
+    const { spectrogramData, ...surface } = getSurface({
+      grid: ctx.grids.get(message.grid),
       origin: ctx.origin,
       query: ctx.query,
       stopTreeCache: ctx.stopTreeCache,
       which: message.which
     })
+
+    ctx.surface = surface
+
+    return { spectrogramData }
   },
   generateDestinationData (ctx, message) {
     const { to, from } = message
@@ -120,13 +123,5 @@ module.exports = createHandler({
       stopTreeCache: ctx.stopTreeCache,
       to: message.point
     })
-  },
-  getSpectrogramData (ctx, message) {
-    return getSpectrogramData({
-      origin: ctx.origin,
-      query: ctx.query,
-      stopTreeCache: ctx.stopTreeCache,
-      grid: ctx.grids.get(message.grid)
-    })
   }
 })