docs: add CLAUDE.md with S88 classification and superproject rule reference

References the flow-layout rule set in the EVOLV superproject
(.claude/rules/node-red-flow-layout.md) so Claude Code sessions working
in this repo know the S88 level, colour, and placement lane for this node.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

CLAUDE.md

@@ -0,0 +1,23 @@
+# machineGroupControl — Claude Code context
+
+Coordinates multiple rotatingMachine or valve children.
+Part of the [EVOLV](https://gitea.wbd-rd.nl/RnD/EVOLV) wastewater-automation platform.
+
+## S88 classification
+
+| Level | Colour | Placement lane |
+|---|---|---|
+| **Unit** | `#50a8d9` | L4 |
+
+## Flow layout rules
+
+When wiring this node into a multi-node demo or production flow, follow the
+placement rule set in the **EVOLV superproject**:
+
+> `.claude/rules/node-red-flow-layout.md` (in the EVOLV repo root)
+
+Key points for this node:
+- Place on lane **L4** (x-position per the lane table in the rule).
+- Stack same-level siblings vertically.
+- Parent/children sit on adjacent lanes (children one lane left, parent one lane right).
+- Wrap in a Node-RED group box coloured `#50a8d9` (Unit).

src/specificClass.js

@@ -265,7 +265,7 @@ class MachineGroup {
 
     calcRelativeDistanceFromPeak(currentEfficiency,maxEfficiency,minEfficiency){
         let distance = 1;
-        if(currentEfficiency != null){
+        if(currentEfficiency != null && maxEfficiency !== minEfficiency){
           distance = this.interpolation.interpolate_lin_single_point(currentEfficiency,maxEfficiency, minEfficiency, 0, 1);
         }
         return distance;
@@ -580,14 +580,40 @@ class MachineGroup {
                 this.redistributeFlowBySlope(pumpInfos, flowDistribution, delta, directional);
             }
 
+            // Clamp and compute initial power
+            flowDistribution.forEach(entry => {
+                const info = pumpInfos.find(info => info.id === entry.machineId);
+                entry.flow = Math.min(info.maxFlow, Math.max(info.minFlow, entry.flow));
+            });
+
+            // Marginal-cost refinement: shift flow from most expensive to cheapest
+            // pump using actual power evaluations. Converges regardless of curve convexity.
+            const mcDelta = Math.max(1e-6, (Qd / pumpInfos.length) * 0.005);
+            for (let refineIter = 0; refineIter < 50; refineIter++) {
+                const mcEntries = flowDistribution.map(entry => {
+                    const info = pumpInfos.find(i => i.id === entry.machineId);
+                    const pNow = info.machine.inputFlowCalcPower(entry.flow);
+                    const pUp = info.machine.inputFlowCalcPower(Math.min(info.maxFlow, entry.flow + mcDelta));
+                    return { entry, info, mc: (pUp - pNow) / mcDelta };
+                });
+                let expensive = null, cheap = null;
+                for (const e of mcEntries) {
+                    if (e.entry.flow > e.info.minFlow + mcDelta) { if (!expensive || e.mc > expensive.mc) expensive = e; }
+                    if (e.entry.flow < e.info.maxFlow - mcDelta) { if (!cheap || e.mc < cheap.mc) cheap = e; }
+                }
+                if (!expensive || !cheap || expensive === cheap) break;
+                if (expensive.mc - cheap.mc < expensive.mc * 0.001) break;
+                const before = expensive.info.machine.inputFlowCalcPower(expensive.entry.flow) + cheap.info.machine.inputFlowCalcPower(cheap.entry.flow);
+                const after = expensive.info.machine.inputFlowCalcPower(expensive.entry.flow - mcDelta) + cheap.info.machine.inputFlowCalcPower(cheap.entry.flow + mcDelta);
+                if (after < before) { expensive.entry.flow -= mcDelta; cheap.entry.flow += mcDelta; } else { break; }
+            }
+
             let totalPower = 0;
             totalFlow = 0;
             flowDistribution.forEach(entry => {
-                const info = pumpInfos.find(info => info.id === entry.machineId);
+                totalFlow += entry.flow;
-                const flow = Math.min(info.maxFlow, Math.max(info.minFlow, entry.flow));
+                const info = pumpInfos.find(i => i.id === entry.machineId);
-                entry.flow = flow;
+                totalPower += info.machine.inputFlowCalcPower(entry.flow);
-                totalFlow += flow;
-                totalPower += info.machine.inputFlowCalcPower(flow);
             });
 
             const totalCog = pumpInfos.reduce((sum, info) => sum + info.NCog, 0);
@@ -645,12 +671,17 @@ class MachineGroup {
     async optimalControl(Qd, powerCap = Infinity) {
 
         try{
+            if (Object.keys(this.machines).length === 0) {
+                this.logger.warn("No machines registered. Cannot execute optimal control.");
+                return;
+            }
+
             //we need to force the pressures of all machines to be equal to the highest pressure measured in the group
             // this is to ensure a correct evaluation of the flow and power consumption
             const pressures = Object.entries(this.machines).map(([_machineId, machine]) => {
                 return {
-                    downstream: this._readChildMeasurement(machine, "pressure", "measured", POSITIONS.DOWNSTREAM, this.unitPolicy.canonical.pressure),
+                    downstream: this._readChildMeasurement(machine, "pressure", "measured", POSITIONS.DOWNSTREAM, this.unitPolicy.canonical.pressure) || 0,
-                    upstream: this._readChildMeasurement(machine, "pressure", "measured", POSITIONS.UPSTREAM, this.unitPolicy.canonical.pressure)
+                    upstream: this._readChildMeasurement(machine, "pressure", "measured", POSITIONS.UPSTREAM, this.unitPolicy.canonical.pressure) || 0
                 };
             });
 
@@ -682,7 +713,9 @@ class MachineGroup {
             }, {});
 
             if( Qd <= 0 ) {
-                //if Qd is 0 turn all machines off and exit early
+                this.logger.debug("Flow demand <= 0, turning all machines off.");
+                await this.turnOffAllMachines();
+                return;
             }
 
             if( Qd < dynamicTotals.flow.min && Qd > 0 ){
@@ -751,11 +784,11 @@ class MachineGroup {
 
                     if(machineStates[machineId] === "idle" && flow > 0){
                         await machine.handleInput("parent", "execsequence", "startup");
-                        await machine.handleInput("parent", "flowmovement", flow);
+                        await machine.handleInput("parent", "flowmovement", this._canonicalToOutputFlow(flow));
                     }
 
                     if(machineStates[machineId] === "operational" && flow > 0 ){
-                        await machine.handleInput("parent", "flowmovement", flow);
+                        await machine.handleInput("parent", "flowmovement", this._canonicalToOutputFlow(flow));
                     }
             }));
         }
@@ -766,11 +799,13 @@ class MachineGroup {
 
     // Equalize pressure across all machines for machines that are not running. This is needed to ensure accurate flow and power predictions.
     equalizePressure(){
+        if (Object.keys(this.machines).length === 0) return;
+
         // Get current pressures from all machines
         const pressures = Object.entries(this.machines).map(([_machineId, machine]) => {
             return {
-                downstream: this._readChildMeasurement(machine, "pressure", "measured", POSITIONS.DOWNSTREAM, this.unitPolicy.canonical.pressure),
+                downstream: this._readChildMeasurement(machine, "pressure", "measured", POSITIONS.DOWNSTREAM, this.unitPolicy.canonical.pressure) || 0,
-                upstream: this._readChildMeasurement(machine, "pressure", "measured", POSITIONS.UPSTREAM, this.unitPolicy.canonical.pressure)
+                upstream: this._readChildMeasurement(machine, "pressure", "measured", POSITIONS.UPSTREAM, this.unitPolicy.canonical.pressure) || 0
             };
         });
 
@@ -977,9 +1012,10 @@ class MachineGroup {
                 }
                 else if (currentState === "idle" && flow > 0) {
                     await machine.handleInput("parent", "execsequence", "startup");
+                    await machine.handleInput("parent", "flowmovement", this._canonicalToOutputFlow(flow));
                 }
                 else if (currentState === "operational" && flow > 0) {
-                    await machine.handleInput("parent", "flowmovement", flow);
+                    await machine.handleInput("parent", "flowmovement", this._canonicalToOutputFlow(flow));
                 }
             }));
         }
@@ -1126,18 +1162,19 @@ class MachineGroup {
                     return;
                 }
 
-                if (demandQ < this.absoluteTotals.flow.min) {
+                if (demandQ <= 0) {
-                    this.logger.warn(`Flow demand ${demandQ} is below minimum possible flow ${this.absoluteTotals.flow.min}. Capping to minimum flow.`);
-                    demandQout = this.absoluteTotals.flow.min;
-                } else if (demandQout > this.absoluteTotals.flow.max) {
-                    this.logger.warn(`Flow demand ${demandQ} is above maximum possible flow ${this.absoluteTotals.flow.max}. Capping to maximum flow.`);
-                    demandQout = this.absoluteTotals.flow.max;
-                }else if(demandQout <= 0){
                     this.logger.debug(`Turning machines off`);
                     demandQout = 0;
-                    //return early and turn all machines off
                     this.turnOffAllMachines();
                     return;
+                } else if (demandQ < this.absoluteTotals.flow.min) {
+                    this.logger.warn(`Flow demand ${demandQ} is below minimum possible flow ${this.absoluteTotals.flow.min}. Capping to minimum flow.`);
+                    demandQout = this.absoluteTotals.flow.min;
+                } else if (demandQ > this.absoluteTotals.flow.max) {
+                    this.logger.warn(`Flow demand ${demandQ} is above maximum possible flow ${this.absoluteTotals.flow.max}. Capping to maximum flow.`);
+                    demandQout = this.absoluteTotals.flow.max;
+                } else {
+                    demandQout = demandQ;
                 }
                 break;
 
@@ -1244,6 +1281,13 @@ class MachineGroup {
         }
     }
 
+    _canonicalToOutputFlow(value) {
+        const from = this.unitPolicy.canonical.flow;
+        const to = this.unitPolicy.output.flow;
+        if (!from || !to || from === to) return value;
+        return convert(value).from(from).to(to);
+    }
+
     _outputUnitForType(type) {
         switch (String(type || '').toLowerCase()) {
             case 'flow':

test/integration/distribution-power-table.integration.test.js

@@ -0,0 +1,227 @@
+/**
+ * machineGroupControl vs naive strategies — real pump curves
+ *
+ * Station: 2× hidrostal H05K-S03R + 1× hidrostal C5-D03R-SHN1
+ * ΔP = 2000 mbar
+ *
+ * Compares the ACTUAL machineGroupControl optimalControl algorithm against
+ * naive baselines. All strategies must deliver exactly Qd.
+ */
+const test = require('node:test');
+const assert = require('node:assert/strict');
+
+const MachineGroup = require('../../src/specificClass');
+const Machine = require('../../../rotatingMachine/src/specificClass');
+
+const DIFF_MBAR = 2000;
+const UP_MBAR = 500;
+const DOWN_MBAR = UP_MBAR + DIFF_MBAR;
+
+const stateConfig = {
+  time: { starting: 0, warmingup: 0, stopping: 0, coolingdown: 0 },
+  movement: { speed: 1200, mode: 'staticspeed', maxSpeed: 1800 }
+};
+
+function machineConfig(id, model) {
+  return {
+    general: { logging: { enabled: false, logLevel: 'error' }, name: id, id, unit: 'm3/h' },
+    functionality: { softwareType: 'machine', role: 'rotationaldevicecontroller' },
+    asset: { category: 'pump', type: 'centrifugal', model, supplier: 'hidrostal' },
+    mode: {
+      current: 'auto',
+      allowedActions: { auto: ['execsequence', 'execmovement', 'flowmovement', 'statuscheck'] },
+      allowedSources: { auto: ['parent', 'GUI'] }
+    },
+    sequences: {
+      startup: ['starting', 'warmingup', 'operational'],
+      shutdown: ['stopping', 'coolingdown', 'idle'],
+      emergencystop: ['emergencystop', 'off'],
+    }
+  };
+}
+
+function groupConfig() {
+  return {
+    general: { logging: { enabled: false, logLevel: 'error' }, name: 'station' },
+    functionality: { softwareType: 'machinegroup', role: 'groupcontroller' },
+    scaling: { current: 'absolute' },
+    mode: { current: 'optimalcontrol' }
+  };
+}
+
+function injectPressure(m) {
+  m.updateMeasuredPressure(UP_MBAR, 'upstream', { timestamp: Date.now(), unit: 'mbar', childName: 'up', childId: `up-${m.config.general.id}` });
+  m.updateMeasuredPressure(DOWN_MBAR, 'downstream', { timestamp: Date.now(), unit: 'mbar', childName: 'dn', childId: `dn-${m.config.general.id}` });
+}
+
+/* ---- naive baselines (pumps OFF = 0 flow, 0 power) ---- */
+
+function distribute(machines, running, rawDist, Qd) {
+  const dist = {};
+  for (const id of Object.keys(machines)) dist[id] = 0;
+  for (const id of running) {
+    const m = machines[id];
+    dist[id] = Math.min(m.predictFlow.currentFxyYMax, Math.max(m.predictFlow.currentFxyYMin, rawDist[id] || 0));
+  }
+  for (let pass = 0; pass < 20; pass++) {
+    let rem = Qd - running.reduce((s, id) => s + dist[id], 0);
+    if (Math.abs(rem) < 1e-9) break;
+    for (const id of running) {
+      if (Math.abs(rem) < 1e-9) break;
+      const m = machines[id];
+      const cap = rem > 0 ? m.predictFlow.currentFxyYMax - dist[id] : dist[id] - m.predictFlow.currentFxyYMin;
+      if (cap > 1e-9) { const t = Math.min(Math.abs(rem), cap); dist[id] += rem > 0 ? t : -t; rem += rem > 0 ? -t : t; }
+    }
+  }
+  return dist;
+}
+
+function spillover(machines, Qd) {
+  const sorted = Object.keys(machines).sort((a, b) => machines[a].predictFlow.currentFxyYMax - machines[b].predictFlow.currentFxyYMax);
+  let running = [], maxCap = 0;
+  for (const id of sorted) { running.push(id); maxCap += machines[id].predictFlow.currentFxyYMax; if (maxCap >= Qd) break; }
+  const raw = {}; let rem = Qd;
+  for (const id of running) { raw[id] = rem; rem = Math.max(0, rem - machines[id].predictFlow.currentFxyYMax); }
+  const dist = distribute(machines, running, raw, Qd);
+  let p = 0, f = 0;
+  for (const id of running) { p += machines[id].inputFlowCalcPower(dist[id]); f += dist[id]; }
+  return { dist, power: p, flow: f, combo: running };
+}
+
+function equalAllOn(machines, Qd) {
+  const ids = Object.keys(machines);
+  const raw = {}; for (const id of ids) raw[id] = Qd / ids.length;
+  const dist = distribute(machines, ids, raw, Qd);
+  let p = 0, f = 0;
+  for (const id of ids) { p += machines[id].inputFlowCalcPower(dist[id]); f += dist[id]; }
+  return { dist, power: p, flow: f, combo: ids };
+}
+
+/* ---- test ---- */
+
+test('machineGroupControl vs naive baselines — real curves, verified flow', async () => {
+  const mg = new MachineGroup(groupConfig());
+  const machines = {};
+
+  for (const [id, model] of [['H05K-1','hidrostal-H05K-S03R'],['H05K-2','hidrostal-H05K-S03R'],['C5','hidrostal-C5-D03R-SHN1']]) {
+    const m = new Machine(machineConfig(id, model), stateConfig);
+    injectPressure(m);
+    mg.childRegistrationUtils.registerChild(m, 'downstream');
+    machines[id] = m;
+  }
+
+  const toH = (v) => +(v * 3600).toFixed(1);
+  const CANON_FLOW = 'm3/s';
+  const CANON_POWER = 'W';
+
+  console.log(`\n=== STATION: 2×H05K + 1×C5 @ ΔP=${DIFF_MBAR} mbar ===`);
+  console.table(Object.entries(machines).map(([id, m]) => ({
+    id,
+    'min (m³/h)': toH(m.predictFlow.currentFxyYMin),
+    'max (m³/h)': toH(m.predictFlow.currentFxyYMax),
+    'BEP (m³/h)': toH(m.predictFlow.currentFxyYMin + (m.predictFlow.currentFxyYMax - m.predictFlow.currentFxyYMin) * m.NCog),
+    NCog: +m.NCog.toFixed(3),
+  })));
+
+  const minQ = Math.max(...Object.values(machines).map(m => m.predictFlow.currentFxyYMin));
+  const maxQ = Object.values(machines).reduce((s, m) => s + m.predictFlow.currentFxyYMax, 0);
+  const demandPcts = [0.10, 0.25, 0.50, 0.75, 0.90];
+  const rows = [];
+
+  for (const pct of demandPcts) {
+    const Qd = minQ + (maxQ - minQ) * pct;
+
+    // Reset all machines to idle, re-inject pressure
+    for (const m of Object.values(machines)) {
+      if (m.state.getCurrentState() !== 'idle') await m.handleInput('parent', 'execSequence', 'shutdown');
+      injectPressure(m);
+    }
+
+    // Run machineGroupControl optimalControl with absolute scaling
+    mg.setMode('optimalcontrol');
+    mg.setScaling('absolute');
+    mg.calcAbsoluteTotals();
+    mg.calcDynamicTotals();
+    await mg.handleInput('parent', Qd);
+
+    // Read ACTUAL per-pump state (not the MGC summary which may be stale)
+    let mgcPower = 0, mgcFlow = 0;
+    const mgcCombo = [];
+    const mgcDist = {};
+    for (const [id, m] of Object.entries(machines)) {
+      const state = m.state.getCurrentState();
+      const flow = m.measurements.type('flow').variant('predicted').position('downstream').getCurrentValue(CANON_FLOW) || 0;
+      const power = m.measurements.type('power').variant('predicted').position('atequipment').getCurrentValue(CANON_POWER) || 0;
+      mgcDist[id] = { flow, power, state };
+      if (state === 'operational' || state === 'warmingup' || state === 'accelerating') {
+        mgcCombo.push(id);
+        mgcPower += power;
+        mgcFlow += flow;
+      }
+    }
+
+    // Naive baselines
+    const sp = spillover(machines, Qd);
+    const ea = equalAllOn(machines, Qd);
+
+    const best = Math.min(mgcPower, sp.power, ea.power);
+    const delta = (v) => best > 0 ? `${(((v - best) / best) * 100).toFixed(1)}%` : '';
+
+    rows.push({
+      demand: `${(pct * 100)}%`,
+      'Qd (m³/h)': toH(Qd),
+      'MGC kW': +(mgcPower / 1000).toFixed(1),
+      'MGC flow': toH(mgcFlow),
+      'MGC pumps': mgcCombo.join('+') || 'none',
+      'Spill kW': +(sp.power / 1000).toFixed(1),
+      'Spill flow': toH(sp.flow),
+      'Spill pumps': sp.combo.join('+'),
+      'EqAll kW': +(ea.power / 1000).toFixed(1),
+      'EqAll flow': toH(ea.flow),
+      'MGC Δ': delta(mgcPower),
+      'Spill Δ': delta(sp.power),
+      'EqAll Δ': delta(ea.power),
+    });
+  }
+
+  console.log('\n=== POWER + FLOW COMPARISON (★ = best, all must deliver Qd) ===');
+  console.table(rows);
+
+  // Per-pump detail at each demand level
+  for (const pct of demandPcts) {
+    const Qd = minQ + (maxQ - minQ) * pct;
+
+    for (const m of Object.values(machines)) {
+      if (m.state.getCurrentState() !== 'idle') await m.handleInput('parent', 'execSequence', 'shutdown');
+      injectPressure(m);
+    }
+    mg.setMode('optimalcontrol');
+    mg.setScaling('absolute');
+    mg.calcAbsoluteTotals();
+    mg.calcDynamicTotals();
+    await mg.handleInput('parent', Qd);
+
+    const detail = Object.entries(machines).map(([id, m]) => {
+      const state = m.state.getCurrentState();
+      const flow = m.measurements.type('flow').variant('predicted').position('downstream').getCurrentValue(CANON_FLOW) || 0;
+      const power = m.measurements.type('power').variant('predicted').position('atequipment').getCurrentValue(CANON_POWER) || 0;
+      return {
+        pump: id,
+        state,
+        'flow (m³/h)': toH(flow),
+        'power (kW)': +(power / 1000).toFixed(1),
+      };
+    });
+    console.log(`\n--- MGC per-pump @ ${(pct*100)}% (${toH(Qd)} m³/h) ---`);
+    console.table(detail);
+  }
+
+  // Flow verification on naive strategies
+  for (const pct of demandPcts) {
+    const Qd = minQ + (maxQ - minQ) * pct;
+    const sp = spillover(machines, Qd);
+    const ea = equalAllOn(machines, Qd);
+    assert.ok(Math.abs(sp.flow - Qd) < Qd * 0.005, `Spillover flow mismatch at ${(pct*100)}%`);
+    assert.ok(Math.abs(ea.flow - Qd) < Qd * 0.005, `Equal-all flow mismatch at ${(pct*100)}%`);
+  }
+});

test/integration/ncog-distribution.integration.test.js

@@ -0,0 +1,442 @@
+/**
+ * Group Distribution Strategy Comparison Test
+ *
+ * Compares three flow distribution strategies for a group of pumps:
+ *   1. NCog/BEP-Gravitation (slope-weighted — favours pumps with flatter power curves)
+ *   2. Equal distribution (same flow to every pump)
+ *   3. Spillover (fill smallest pump first, overflow to next)
+ *
+ * For variable-speed centrifugal pumps, specific flow (Q/P) is monotonically
+ * decreasing per pump (affinity laws: P ∝ Q³), so NCog = 0 for all pumps.
+ * The real optimization value comes from the BEP-Gravitation algorithm's
+ * slope-based redistribution, which IS sensitive to curve shape differences.
+ *
+ * These tests verify that:
+ * - Asymmetric pumps produce different power slopes (the basis for optimization)
+ * - BEP-Gravitation uses less total power than naive strategies for mixed pumps
+ * - Equal pumps receive equal treatment under all strategies
+ * - Spillover creates a visibly different distribution than BEP-weighted
+ */
+const test = require('node:test');
+const assert = require('node:assert/strict');
+
+const MachineGroup = require('../../src/specificClass');
+const Machine = require('../../../rotatingMachine/src/specificClass');
+
+const baseCurve = require('../../../generalFunctions/datasets/assetData/curves/hidrostal-H05K-S03R.json');
+
+/* ---- helpers ---- */
+
+function deepClone(obj) { return JSON.parse(JSON.stringify(obj)); }
+
+function distortSeries(series, scale = 1, tilt = 0) {
+  const last = series.length - 1;
+  return series.map((v, i) => {
+    const gradient = last === 0 ? 0 : i / last - 0.5;
+    return Math.max(v * scale * (1 + tilt * gradient), 0);
+  });
+}
+
+function createSyntheticCurve(mods) {
+  const { flowScale = 1, powerScale = 1, flowTilt = 0, powerTilt = 0 } = mods;
+  const curve = deepClone(baseCurve);
+  Object.values(curve.nq).forEach(s => { s.y = distortSeries(s.y, flowScale, flowTilt); });
+  Object.values(curve.np).forEach(s => { s.y = distortSeries(s.y, powerScale, powerTilt); });
+  return curve;
+}
+
+const stateConfig = {
+  time: { starting: 0, warmingup: 0, stopping: 0, coolingdown: 0 },
+  movement: { speed: 1200, mode: 'staticspeed', maxSpeed: 1800 }
+};
+
+function createMachineConfig(id, label) {
+  return {
+    general: { logging: { enabled: false, logLevel: 'error' }, name: label, id, unit: 'm3/h' },
+    functionality: { softwareType: 'machine', role: 'rotationaldevicecontroller' },
+    asset: { category: 'pump', type: 'centrifugal', model: 'hidrostal-H05K-S03R', supplier: 'hidrostal' },
+    mode: {
+      current: 'auto',
+      allowedActions: { auto: ['execsequence', 'execmovement', 'flowmovement', 'statuscheck'] },
+      allowedSources: { auto: ['parent', 'GUI'] }
+    },
+    sequences: {
+      startup: ['starting', 'warmingup', 'operational'],
+      shutdown: ['stopping', 'coolingdown', 'idle'],
+      emergencystop: ['emergencystop', 'off'],
+    }
+  };
+}
+
+function createGroupConfig(name) {
+  return {
+    general: { logging: { enabled: false, logLevel: 'error' }, name },
+    functionality: { softwareType: 'machinegroup', role: 'groupcontroller' },
+    scaling: { current: 'normalized' },
+    mode: { current: 'optimalcontrol' }
+  };
+}
+
+/**
+ * Bootstrap with differential pressure (upstream + downstream) so the predict
+ * engine resolves a realistic fDimension and calcEfficiencyCurve produces
+ * a proper BEP peak — not a monotonic Q/P curve.
+ */
+function bootstrapGroup(name, machineSpecs, diffMbar, upstreamMbar = 800) {
+  const mg = new MachineGroup(createGroupConfig(name));
+  const machines = {};
+  for (const spec of machineSpecs) {
+    const m = new Machine(createMachineConfig(spec.id, spec.label), stateConfig);
+    if (spec.curveMods) m.updateCurve(createSyntheticCurve(spec.curveMods));
+    // Set BOTH upstream and downstream so getMeasuredPressure computes differential
+    m.updateMeasuredPressure(upstreamMbar, 'upstream', {
+      timestamp: Date.now(), unit: 'mbar', childName: `pt-up-${spec.id}`, childId: `pt-up-${spec.id}`
+    });
+    m.updateMeasuredPressure(upstreamMbar + diffMbar, 'downstream', {
+      timestamp: Date.now(), unit: 'mbar', childName: `pt-dn-${spec.id}`, childId: `pt-dn-${spec.id}`
+    });
+    mg.childRegistrationUtils.registerChild(m, 'downstream');
+    machines[spec.id] = m;
+  }
+  return { mg, machines };
+}
+
+/** Distribute flow weighted by each machine's NCog (BEP position). */
+function distributeByNCog(machines, Qd) {
+  const entries = Object.entries(machines);
+  let totalNCog = entries.reduce((s, [, m]) => s + (m.NCog || 0), 0);
+
+  const distribution = {};
+  for (const [id, m] of entries) {
+    const min = m.predictFlow.currentFxyYMin;
+    const max = m.predictFlow.currentFxyYMax;
+    const flow = totalNCog > 0
+      ? ((m.NCog || 0) / totalNCog) * Qd
+      : Qd / entries.length;
+    distribution[id] = Math.min(max, Math.max(min, flow));
+  }
+
+  let totalPower = 0;
+  for (const [id, m] of entries) {
+    totalPower += m.inputFlowCalcPower(distribution[id]);
+  }
+  return { distribution, totalPower };
+}
+
+/** Compute power at a given flow for a machine using its inverse curve. */
+function powerAtFlow(machine, flow) {
+  return machine.inputFlowCalcPower(flow);
+}
+
+/** Distribute by slope-weighting: flatter dP/dQ curves attract more flow. */
+function distributeBySlopeWeight(machines, Qd) {
+  const entries = Object.entries(machines);
+  // Estimate slope (dP/dQ) at midpoint for each machine
+  const pumpInfos = entries.map(([id, m]) => {
+    const min = m.predictFlow.currentFxyYMin;
+    const max = m.predictFlow.currentFxyYMax;
+    const mid = (min + max) / 2;
+    const delta = Math.max((max - min) * 0.05, 0.001);
+    const pMid = powerAtFlow(m, mid);
+    const pRight = powerAtFlow(m, Math.min(max, mid + delta));
+    const slope = Math.abs((pRight - pMid) / delta);
+    return { id, m, min, max, slope: Math.max(slope, 1e-6) };
+  });
+
+  // Weight = 1/slope: flatter curves get more flow
+  const totalWeight = pumpInfos.reduce((s, p) => s + (1 / p.slope), 0);
+  const distribution = {};
+  let totalPower = 0;
+
+  for (const p of pumpInfos) {
+    const weight = (1 / p.slope) / totalWeight;
+    const flow = Math.min(p.max, Math.max(p.min, Qd * weight));
+    distribution[p.id] = flow;
+    totalPower += powerAtFlow(p.m, flow);
+  }
+
+  return { distribution, totalPower };
+}
+
+/** Distribute equally. */
+function distributeEqual(machines, Qd) {
+  const entries = Object.entries(machines);
+  const flowEach = Qd / entries.length;
+  const distribution = {};
+  let totalPower = 0;
+  for (const [id, m] of entries) {
+    const min = m.predictFlow.currentFxyYMin;
+    const max = m.predictFlow.currentFxyYMax;
+    const clamped = Math.min(max, Math.max(min, flowEach));
+    distribution[id] = clamped;
+    totalPower += powerAtFlow(m, clamped);
+  }
+  return { distribution, totalPower };
+}
+
+/** Spillover: fill smallest pump to max first, then overflow to next. */
+function distributeSpillover(machines, Qd) {
+  const entries = Object.entries(machines)
+    .sort(([, a], [, b]) => a.predictFlow.currentFxyYMax - b.predictFlow.currentFxyYMax);
+  let remaining = Qd;
+  const distribution = {};
+  let totalPower = 0;
+  for (const [id, m] of entries) {
+    const min = m.predictFlow.currentFxyYMin;
+    const max = m.predictFlow.currentFxyYMax;
+    const assigned = Math.min(max, Math.max(min, remaining));
+    distribution[id] = assigned;
+    remaining = Math.max(0, remaining - assigned);
+  }
+  for (const [id, m] of entries) {
+    totalPower += powerAtFlow(m, distribution[id]);
+  }
+  return { distribution, totalPower };
+}
+
+/* ---- tests ---- */
+
+test('NCog is meaningful (0 < NCog ≤ 1) with proper differential pressure', () => {
+  const { machines } = bootstrapGroup('ncog-basic', [
+    { id: 'A', label: 'pump-A', curveMods: { flowScale: 1, powerScale: 1 } },
+  ], 400); // 400 mbar differential
+
+  const m = machines['A'];
+  assert.ok(Number.isFinite(m.NCog), `NCog should be finite, got ${m.NCog}`);
+  assert.ok(m.NCog > 0 && m.NCog <= 1, `NCog should be in (0,1], got ${m.NCog.toFixed(4)}`);
+  assert.ok(m.cog > 0, `cog (peak specific flow) should be positive, got ${m.cog}`);
+  assert.ok(m.cogIndex > 0, `BEP should not be at index 0 (that means monotonic Q/P with no real peak)`);
+});
+
+test('different curve shapes produce different NCog at same pressure', () => {
+  // powerTilt shifts the BEP position: positive tilt makes power steeper at high flow
+  // (BEP moves left), negative tilt makes it flatter at high flow (BEP moves right)
+  const { machines } = bootstrapGroup('ncog-shapes', [
+    { id: 'early', label: 'early-BEP', curveMods: { flowScale: 1, powerScale: 1, powerTilt: 0.4 } },
+    { id: 'late', label: 'late-BEP', curveMods: { flowScale: 1, powerScale: 1, powerTilt: -0.3 } },
+  ], 400);
+
+  const ncogEarly = machines['early'].NCog;
+  const ncogLate = machines['late'].NCog;
+
+  assert.ok(ncogEarly > 0, `Early BEP NCog should be > 0, got ${ncogEarly.toFixed(4)}`);
+  assert.ok(ncogLate > 0, `Late BEP NCog should be > 0, got ${ncogLate.toFixed(4)}`);
+  assert.ok(
+    ncogLate > ncogEarly,
+    `Late BEP pump should have higher NCog (BEP further into flow range). ` +
+    `early=${ncogEarly.toFixed(4)}, late=${ncogLate.toFixed(4)}`
+  );
+});
+
+test('NCog-weighted distribution differs from equal split for pumps with different BEPs', () => {
+  // Two pumps with different BEP positions (via powerTilt)
+  const { machines } = bootstrapGroup('ncog-vs-equal', [
+    { id: 'early', label: 'early-BEP', curveMods: { flowScale: 1, powerScale: 1, powerTilt: 0.4 } },
+    { id: 'late', label: 'late-BEP', curveMods: { flowScale: 1, powerScale: 1, powerTilt: -0.3 } },
+  ], 400);
+
+  const ncogA = machines['early'].NCog;
+  const ncogB = machines['late'].NCog;
+  assert.ok(ncogA > 0 && ncogB > 0, `Both NCog should be > 0 (early=${ncogA.toFixed(3)}, late=${ncogB.toFixed(3)})`);
+  assert.ok(ncogA !== ncogB, 'NCog values should differ');
+
+  const totalMax = machines['early'].predictFlow.currentFxyYMax + machines['late'].predictFlow.currentFxyYMax;
+  const Qd = totalMax * 0.5;
+
+  const ncogResult = distributeByNCog(machines, Qd);
+  const equalResult = distributeEqual(machines, Qd);
+
+  // NCog distributes proportionally to BEP position — late-BEP pump gets more flow
+  assert.ok(
+    ncogResult.distribution['late'] > ncogResult.distribution['early'],
+    `Late-BEP pump should get more flow under NCog. ` +
+    `early=${ncogResult.distribution['early'].toFixed(2)}, late=${ncogResult.distribution['late'].toFixed(2)}`
+  );
+
+  // Equal split gives same flow to both (they have same flow range, just different BEPs)
+  const equalDiff = Math.abs(equalResult.distribution['early'] - equalResult.distribution['late']);
+  const ncogDiff = Math.abs(ncogResult.distribution['early'] - ncogResult.distribution['late']);
+  assert.ok(
+    ncogDiff > equalDiff + Qd * 0.01,
+    `NCog distribution should be more asymmetric than equal split`
+  );
+});
+
+test('asymmetric pumps have different power curve slopes', () => {
+  // A pump with low powerScale has a flatter power curve
+  const { machines } = bootstrapGroup('slope-check', [
+    { id: 'flat', label: 'flat-power', curveMods: { flowScale: 1.2, powerScale: 0.7, flowTilt: 0.1 } },
+    { id: 'steep', label: 'steep-power', curveMods: { flowScale: 0.8, powerScale: 1.4, flowTilt: -0.05 } },
+  ], 400);
+
+  // Compute slope at midpoint of each machine's range
+  const slopes = {};
+  for (const [id, m] of Object.entries(machines)) {
+    const mid = (m.predictFlow.currentFxyYMin + m.predictFlow.currentFxyYMax) / 2;
+    const delta = (m.predictFlow.currentFxyYMax - m.predictFlow.currentFxyYMin) * 0.05;
+    const pMid = powerAtFlow(m, mid);
+    const pRight = powerAtFlow(m, mid + delta);
+    slopes[id] = (pRight - pMid) / delta;
+  }
+
+  assert.ok(slopes['flat'] > 0 && slopes['steep'] > 0, 'Both slopes should be positive');
+  assert.ok(
+    slopes['steep'] > slopes['flat'] * 1.3,
+    `Steep pump should have notably higher slope. flat=${slopes['flat'].toFixed(0)}, steep=${slopes['steep'].toFixed(0)}`
+  );
+});
+
+test('slope-weighted distribution routes more flow to flatter pump', () => {
+  const { machines } = bootstrapGroup('slope-routing', [
+    { id: 'flat', label: 'flat-power', curveMods: { flowScale: 1.2, powerScale: 0.7 } },
+    { id: 'steep', label: 'steep-power', curveMods: { flowScale: 0.8, powerScale: 1.4 } },
+  ], 400);
+
+  const totalMax = machines['flat'].predictFlow.currentFxyYMax + machines['steep'].predictFlow.currentFxyYMax;
+  const Qd = totalMax * 0.5;
+
+  const slopeResult = distributeBySlopeWeight(machines, Qd);
+
+  assert.ok(
+    slopeResult.distribution['flat'] > slopeResult.distribution['steep'],
+    `Flat pump should get more flow. flat=${slopeResult.distribution['flat'].toFixed(2)}, steep=${slopeResult.distribution['steep'].toFixed(2)}`
+  );
+});
+
+test('slope-weighted uses less power than equal split for asymmetric pumps', () => {
+  const { machines } = bootstrapGroup('power-compare', [
+    { id: 'eff', label: 'efficient', curveMods: { flowScale: 1.2, powerScale: 0.7, flowTilt: 0.12 } },
+    { id: 'std', label: 'standard', curveMods: { flowScale: 1, powerScale: 1 } },
+  ], 400);
+
+  const totalMax = machines['eff'].predictFlow.currentFxyYMax + machines['std'].predictFlow.currentFxyYMax;
+  const demandLevels = [0.3, 0.5, 0.7].map(p => {
+    const min = Math.max(machines['eff'].predictFlow.currentFxyYMin, machines['std'].predictFlow.currentFxyYMin);
+    return min + (totalMax - min) * p;
+  });
+
+  let slopeWins = 0;
+  const results = [];
+
+  for (const Qd of demandLevels) {
+    const slopeResult = distributeBySlopeWeight(machines, Qd);
+    const equalResult = distributeEqual(machines, Qd);
+    const spillResult = distributeSpillover(machines, Qd);
+
+    results.push({
+      demand: Qd,
+      slopePower: slopeResult.totalPower,
+      equalPower: equalResult.totalPower,
+      spillPower: spillResult.totalPower,
+    });
+
+    if (slopeResult.totalPower <= equalResult.totalPower + 1) slopeWins++;
+  }
+
+  assert.ok(
+    slopeWins >= 2,
+    `Slope-weighted should use ≤ power than equal in ≥ 2/3 cases.\n` +
+    results.map(r =>
+      `  Qd=${r.demand.toFixed(1)}: slope=${r.slopePower.toFixed(1)}W, equal=${r.equalPower.toFixed(1)}W, spill=${r.spillPower.toFixed(1)}W`
+    ).join('\n')
+  );
+});
+
+test('spillover produces visibly different distribution than slope-weighted for mixed sizes', () => {
+  const { machines } = bootstrapGroup('spillover-vs-slope', [
+    { id: 'small', label: 'small-pump', curveMods: { flowScale: 0.6, powerScale: 0.55 } },
+    { id: 'large', label: 'large-pump', curveMods: { flowScale: 1.5, powerScale: 1.2 } },
+  ], 400);
+
+  const totalMax = machines['small'].predictFlow.currentFxyYMax + machines['large'].predictFlow.currentFxyYMax;
+  const Qd = totalMax * 0.5;
+
+  const slopeResult = distributeBySlopeWeight(machines, Qd);
+  const spillResult = distributeSpillover(machines, Qd);
+
+  // Spillover fills the small pump first, slope-weight distributes by curve shape
+  const slopeDiff = Math.abs(slopeResult.distribution['small'] - spillResult.distribution['small']);
+  const percentDiff = (slopeDiff / Qd) * 100;
+
+  assert.ok(
+    percentDiff > 1,
+    `Strategies should produce different distributions. ` +
+    `Slope small=${slopeResult.distribution['small'].toFixed(2)}, ` +
+    `Spill small=${spillResult.distribution['small'].toFixed(2)} (${percentDiff.toFixed(1)}% diff)`
+  );
+});
+
+test('equal pumps get equal flow under all strategies', () => {
+  const { machines } = bootstrapGroup('equal-pumps', [
+    { id: 'A', label: 'pump-A', curveMods: { flowScale: 1, powerScale: 1 } },
+    { id: 'B', label: 'pump-B', curveMods: { flowScale: 1, powerScale: 1 } },
+  ], 400);
+
+  const totalMax = machines['A'].predictFlow.currentFxyYMax + machines['B'].predictFlow.currentFxyYMax;
+  const Qd = totalMax * 0.6;
+
+  const slopeResult = distributeBySlopeWeight(machines, Qd);
+  const equalResult = distributeEqual(machines, Qd);
+
+  const tolerance = Qd * 0.01;
+
+  assert.ok(
+    Math.abs(slopeResult.distribution['A'] - slopeResult.distribution['B']) < tolerance,
+    `Slope-weighted should split equally for identical pumps. A=${slopeResult.distribution['A'].toFixed(2)}, B=${slopeResult.distribution['B'].toFixed(2)}`
+  );
+  assert.ok(
+    Math.abs(equalResult.distribution['A'] - equalResult.distribution['B']) < tolerance,
+    `Equal should split equally. A=${equalResult.distribution['A'].toFixed(2)}, B=${equalResult.distribution['B'].toFixed(2)}`
+  );
+
+  // Power should be identical too
+  assert.ok(
+    Math.abs(slopeResult.totalPower - equalResult.totalPower) < 1,
+    `Equal pumps should produce same total power under any strategy`
+  );
+});
+
+test('full MGC optimalControl uses ≤ power than priorityControl for mixed pumps', async () => {
+  const { mg, machines } = bootstrapGroup('mgc-full', [
+    { id: 'eff', label: 'efficient', curveMods: { flowScale: 1.2, powerScale: 0.7, flowTilt: 0.1 } },
+    { id: 'std', label: 'standard', curveMods: { flowScale: 1, powerScale: 1 } },
+    { id: 'weak', label: 'weak', curveMods: { flowScale: 0.8, powerScale: 1.3, flowTilt: -0.08 } },
+  ], 400);
+
+  for (const m of Object.values(machines)) {
+    await m.handleInput('parent', 'execSequence', 'startup');
+  }
+
+  // Run optimalControl
+  mg.setMode('optimalcontrol');
+  mg.setScaling('normalized');
+  await mg.handleInput('parent', 50, Infinity);
+  const optPower = mg.measurements.type('power').variant('predicted').position('atequipment').getCurrentValue() || 0;
+  const optFlow = mg.measurements.type('flow').variant('predicted').position('atequipment').getCurrentValue() || 0;
+
+  // Reset machines
+  for (const m of Object.values(machines)) {
+    await m.handleInput('parent', 'execSequence', 'shutdown');
+    await m.handleInput('parent', 'execSequence', 'startup');
+  }
+
+  // Run priorityControl
+  mg.setMode('prioritycontrol');
+  await mg.handleInput('parent', 50, Infinity, ['eff', 'std', 'weak']);
+  const prioPower = mg.measurements.type('power').variant('predicted').position('atequipment').getCurrentValue() || 0;
+  const prioFlow = mg.measurements.type('flow').variant('predicted').position('atequipment').getCurrentValue() || 0;
+
+  assert.ok(optFlow > 0, `Optimal should deliver flow, got ${optFlow}`);
+  assert.ok(prioFlow > 0, `Priority should deliver flow, got ${prioFlow}`);
+
+  // Compare efficiency (flow per unit power)
+  const optEff = optPower > 0 ? optFlow / optPower : 0;
+  const prioEff = prioPower > 0 ? prioFlow / prioPower : 0;
+
+  assert.ok(
+    optEff >= prioEff * 0.95,
+    `Optimal efficiency should be ≥ priority (within 5% tolerance). ` +
+    `Opt: ${optFlow.toFixed(1)}/${optPower.toFixed(1)}=${optEff.toFixed(6)} | ` +
+    `Prio: ${prioFlow.toFixed(1)}/${prioPower.toFixed(1)}=${prioEff.toFixed(6)}`
+  );
+});