Compute CredData from TimelineCredScores (#1831)

This commit adds the `analysis/credData` module, which processes raw
TimelineCredScores into a format which is better for serialization and
data analysis. In particular, this format explicitly stores the summary
(summed-across-time) data for nodes separately from the raw temporal
data, which will allow us to throw away raw data for uninteresting or
low-cred nodes, while keeping the summary.

Test plan: I've added some basic unit tests; run `yarn test`.

src/analysis/credData.js

@@ -0,0 +1,124 @@
+// @flow
+
+import type {TimestampMs} from "../util/timestamp";
+import type {TimelineCredScores} from "../core/algorithm/distributionToCred";
+
+/**
+ * Comprehensive data on a cred distribution.
+ */
+export type CredData = {|
+  // Cred level information, always stored in graph address order.
+  +nodeSummaries: $ReadOnlyArray<NodeCredSummary>,
+  +nodeOverTime: $ReadOnlyArray<NodeCredOverTime | null>,
+  +edgeSummaries: $ReadOnlyArray<EdgeCredSummary>,
+  +edgeOverTime: $ReadOnlyArray<EdgeCredOverTime | null>,
+  +intervalEnds: $ReadOnlyArray<TimestampMs>,
+|};
+
+/** Summary of a node's cred across all time.
+ *
+ * CredData includes this information for every node in the graph, regardless of its score.
+ */
+export type NodeCredSummary = {|
+  +cred: number,
+  +seedFlow: number,
+  +syntheticLoopFlow: number,
+|};
+
+/**
+ * A node's cred data at interval time resolution.
+ *
+ * To save space, the CredData may filter out the NodeCredOverTime entirely
+ * for nodes with low score, or may filter out the seedFlow or syntheticLoopFlow
+ * fields if either was trivial.
+ */
+export type NodeCredOverTime = {|
+  +cred: $ReadOnlyArray<number>,
+  +seedFlow: $ReadOnlyArray<number> | null,
+  +syntheticLoopFlow: $ReadOnlyArray<number> | null,
+|};
+
+/**
+ * An edge's cred flows across all time.
+ *
+ * CredData includes this for every edge in the graph, regardless of its cred flows.
+ */
+export type EdgeCredSummary = {|
+  +forwardFlow: number,
+  +backwardFlow: number,
+|};
+
+/**
+ * An edge's cred flows at interval time resolution.
+ *
+ * To save space, we may filter out this struct entirely for low-cred-flow edges, or we might
+ * skip either the forwardFlow or backwardFlow fields if it had negligible cred flows in either direction.
+ */
+export type EdgeCredOverTime = {|
+  +forwardFlow: $ReadOnlyArray<number> | null,
+  +backwardFlow: $ReadOnlyArray<number> | null,
+|};
+
+export function computeCredData(scores: TimelineCredScores): CredData {
+  const numIntervals = scores.length;
+  if (numIntervals === 0) {
+    return {
+      nodeSummaries: [],
+      nodeOverTime: [],
+      edgeSummaries: [],
+      edgeOverTime: [],
+      intervalEnds: [],
+    };
+  }
+  const intervalEnds = scores.map((x) => x.interval.endTimeMs);
+  const numNodes = scores[0].cred.length;
+  const numEdges = scores[0].forwardFlow.length;
+  const nodeSummaries = new Array(numNodes).fill(null).map(() => ({
+    cred: 0,
+    seedFlow: 0,
+    syntheticLoopFlow: 0,
+  }));
+  const nodeOverTime = new Array(numNodes).fill(null).map(() => ({
+    cred: new Array(numIntervals),
+    seedFlow: new Array(numIntervals),
+    syntheticLoopFlow: new Array(numIntervals),
+  }));
+  const edgeSummaries = new Array(numEdges).fill(null).map(() => ({
+    forwardFlow: 0,
+    backwardFlow: 0,
+  }));
+  const edgeOverTime = new Array(numEdges).fill(null).map(() => ({
+    forwardFlow: new Array(numIntervals),
+    backwardFlow: new Array(numIntervals),
+  }));
+  for (let i = 0; i < numIntervals; i++) {
+    const {
+      cred,
+      forwardFlow,
+      backwardFlow,
+      seedFlow,
+      syntheticLoopFlow,
+    } = scores[i];
+    for (let n = 0; n < numNodes; n++) {
+      nodeSummaries[n].cred += cred[n];
+      nodeOverTime[n].cred[i] = cred[n];
+      nodeSummaries[n].seedFlow += seedFlow[n];
+      nodeOverTime[n].seedFlow[i] = seedFlow[n];
+      nodeSummaries[n].syntheticLoopFlow += syntheticLoopFlow[n];
+      nodeOverTime[n].syntheticLoopFlow[i] = syntheticLoopFlow[n];
+    }
+    for (let e = 0; e < numEdges; e++) {
+      edgeSummaries[e].forwardFlow += forwardFlow[e];
+      edgeOverTime[e].forwardFlow[i] = forwardFlow[e];
+      edgeSummaries[e].backwardFlow += backwardFlow[e];
+      edgeOverTime[e].backwardFlow[i] = backwardFlow[e];
+    }
+  }
+  return {
+    nodeSummaries,
+    nodeOverTime,
+    edgeSummaries,
+    edgeOverTime,
+    intervalEnds,
+  };
+}

src/analysis/credData.test.js

@@ -0,0 +1,55 @@
+// @flow
+
+import {computeCredData} from "./credData";
+import type {TimelineCredScores} from "../core/algorithm/distributionToCred";
+
+describe("src/analysis/credData", () => {
+  it("handles empty scores correctly", () => {
+    expect(computeCredData([])).toEqual({
+      nodeSummaries: [],
+      nodeOverTime: [],
+      edgeSummaries: [],
+      edgeOverTime: [],
+      intervalEnds: [],
+    });
+  });
+  it("handles non-empty scores correctly", () => {
+    const scores: TimelineCredScores = [
+      {
+        interval: {startTimeMs: 0, endTimeMs: 100},
+        cred: new Float64Array([4, 5]),
+        forwardFlow: new Float64Array([1]),
+        backwardFlow: new Float64Array([2]),
+        seedFlow: new Float64Array([0, 1]),
+        syntheticLoopFlow: new Float64Array([0.1, 0]),
+      },
+      {
+        interval: {startTimeMs: 100, endTimeMs: 200},
+        cred: new Float64Array([10, 1]),
+        forwardFlow: new Float64Array([1]),
+        backwardFlow: new Float64Array([0]),
+        seedFlow: new Float64Array([0, 1]),
+        syntheticLoopFlow: new Float64Array([0.1, 0]),
+      },
+    ];
+    const expected = {
+      intervalEnds: [100, 200],
+      nodeSummaries: [
+        {cred: 14, seedFlow: 0, syntheticLoopFlow: 0.2},
+        {cred: 6, seedFlow: 2, syntheticLoopFlow: 0},
+      ],
+      nodeOverTime: [
+        {cred: [4, 10], seedFlow: [0, 0], syntheticLoopFlow: [0.1, 0.1]},
+        {cred: [5, 1], seedFlow: [1, 1], syntheticLoopFlow: [0, 0]},
+      ],
+      edgeSummaries: [
+        {
+          forwardFlow: 2,
+          backwardFlow: 2,
+        },
+      ],
+      edgeOverTime: [{forwardFlow: [1, 1], backwardFlow: [2, 0]}],
+    };
+    expect(computeCredData(scores)).toEqual(expected);
+  });
+});

src/core/algorithm/distributionToCred.js

@@ -10,8 +10,8 @@ import {type Interval} from "../interval";
 import {type TimelineDistributions} from "./timelinePagerank";
 import {NodeAddress, type NodeAddressT} from "../../core/graph";
 
-export opaque type NodeOrderedCredScores: Float64Array = Float64Array;
-export opaque type EdgeOrderedCredScores: Float64Array = Float64Array;
+export type NodeOrderedCredScores = Float64Array;
+export type EdgeOrderedCredScores = Float64Array;
 
 /**
  * Represents cred scores over time.