Merge pull request #398 from xenharmonic-devs/lightweight-tempering

Implement lightweight tempering algorithms for large subgroups

src/__tests__/tempering.spec.ts

@@ -7,9 +7,40 @@ import {
   makeRank2FromVals,
   mosPatternsRank2FromCommas,
   mosPatternsRank2FromVals,
+  toPrimeMapping,
 } from "../tempering";
-import { arraysEqual, Fraction, valueToCents } from "xen-dev-utils";
+import {
+  arraysEqual,
+  Fraction,
+  PRIME_CENTS,
+  valueToCents,
+} from "xen-dev-utils";
 import { ExtendedMonzo, Interval, Scale } from "scale-workshop-core";
+import { Subgroup } from "temperaments";
+import { DEFAULT_NUMBER_OF_COMPONENTS } from "../constants";
+
+describe("Prime map converter", () => {
+  it("does (almost) nothing in 5-limit JI", () => {
+    const fiveLimit = PRIME_CENTS.slice(0, 3);
+    const mapping = toPrimeMapping(fiveLimit, new Subgroup(5));
+    expect(mapping[0]).toBeCloseTo(fiveLimit[0]);
+    expect(mapping[1]).toBeCloseTo(fiveLimit[1]);
+    expect(mapping[2]).toBeCloseTo(fiveLimit[2]);
+    expect(mapping.length).toBe(DEFAULT_NUMBER_OF_COMPONENTS);
+    expect(mapping[3]).toBeCloseTo(PRIME_CENTS[3]);
+  });
+
+  it("converts a mapping in 2.3.13/5 to 2.3.5.7.11.13...", () => {
+    const original = [1200, 1901, 1654];
+    const mapping = toPrimeMapping(original, new Subgroup("2.3.13/5"));
+    expect(mapping[0]).toBeCloseTo(1200);
+    expect(mapping[1]).toBeCloseTo(1901);
+    expect(mapping[3]).toBeCloseTo(PRIME_CENTS[3]);
+    expect(mapping[4]).toBeCloseTo(PRIME_CENTS[4]);
+    expect(mapping[5] - mapping[2]).toBeCloseTo(1654);
+    expect(mapping[6]).toBeCloseTo(PRIME_CENTS[6]);
+  });
+});
 
 describe("Temperament Mapping", () => {
   it("calculates POTE meantone", () => {

src/components/modals/generation/RankTwo.vue

@@ -1,5 +1,8 @@
 <script setup lang="ts">
-import { DEFAULT_NUMBER_OF_COMPONENTS } from "@/constants";
+import {
+  DEFAULT_NUMBER_OF_COMPONENTS,
+  MAX_INTERACTIVE_SUBGROUP_SIZE,
+} from "@/constants";
 import {
   makeRank2FromVals,
   makeRank2FromCommas,
@@ -105,7 +108,7 @@ const [mosPatterns, mosPatternsError] = computedAndError(() => {
       return [];
     }
     // Huge subgroups get too expensive to evaluate interactively
-    if (subgroup.value.basis.length > 6) {
+    if (subgroup.value.basis.length > MAX_INTERACTIVE_SUBGROUP_SIZE) {
       return expensiveMosPatterns.value;
     }
     return mosPatternsRank2FromVals(
@@ -121,7 +124,7 @@ const [mosPatterns, mosPatternsError] = computedAndError(() => {
       return [];
     }
     // Huge subgroups get too expensive to evaluate interactively
-    if (subgroup.value.basis.length > 6) {
+    if (subgroup.value.basis.length > MAX_INTERACTIVE_SUBGROUP_SIZE) {
       return expensiveMosPatterns.value;
     }
     return mosPatternsRank2FromCommas(

src/components/modals/modification/TemperScale.vue

@@ -1,11 +1,14 @@
 <script setup lang="ts">
-import { DEFAULT_NUMBER_OF_COMPONENTS } from "@/constants";
-import { Mapping, stretchToEdo } from "@/tempering";
+import {
+  DEFAULT_NUMBER_OF_COMPONENTS,
+  MAX_GEO_SUBGROUP_SIZE,
+} from "@/constants";
+import { Mapping, stretchToEdo, toPrimeMapping } from "@/tempering";
 import { computed, ref, watch } from "vue";
 import Modal from "@/components/ModalDialog.vue";
 import { makeState, splitText } from "@/components/modals/tempering-state";
 import { add, Fraction, PRIME_CENTS } from "xen-dev-utils";
-import { mapByVal, resolveMonzo } from "temperaments";
+import { mapByVal, resolveMonzo, tenneyVals, vanishCommas } from "temperaments";
 import {
   ExtendedMonzo,
   Interval,
@@ -48,6 +51,10 @@ const subgroup = state.subgroup;
 const options = state.options;
 const edoUnavailable = computed(() => vals.value.length !== 1);
 
+const constraintsDisabled = computed(
+  () => subgroup.value.basis.length > MAX_GEO_SUBGROUP_SIZE
+);
+
 watch(subgroupError, (newValue) =>
   subgroupInput.value!.setCustomValidity(newValue)
 );
@@ -128,19 +135,57 @@ function modify() {
         }
         mapping = new Mapping(vector.slice(0, DEFAULT_NUMBER_OF_COMPONENTS));
       } else if (method.value === "vals") {
-        mapping = Mapping.fromVals(
-          vals.value,
-          DEFAULT_NUMBER_OF_COMPONENTS,
-          subgroup.value,
-          options.value
-        );
+        if (constraintsDisabled.value) {
+          // Subgroup is too large to use geometric methods. Use O(n²) projection instead.
+          const weights = options.value.weights;
+          // True constraints are not supported so CTE is interpreted as POTE.
+          const temperEquaves =
+            options.value.temperEquaves && tempering.value !== "CTE";
+          const jip = subgroup.value.jip();
+          const valVectors = vals.value.map((val) =>
+            subgroup.value.fromWarts(val)
+          );
+          let mappingVector = tenneyVals(valVectors, jip, weights);
+          if (!temperEquaves) {
+            mappingVector = mappingVector.map(
+              (m) => (jip[0] * m) / mappingVector[0]
+            );
+          }
+          mapping = new Mapping(toPrimeMapping(mappingVector, subgroup.value));
+        } else {
+          mapping = Mapping.fromVals(
+            vals.value,
+            DEFAULT_NUMBER_OF_COMPONENTS,
+            subgroup.value,
+            options.value
+          );
+        }
       } else {
-        mapping = Mapping.fromCommas(
-          commas.value,
-          DEFAULT_NUMBER_OF_COMPONENTS,
-          subgroup.value,
-          options.value
-        );
+        if (constraintsDisabled.value) {
+          // Subgroup is too large to use geometric methods. Use O(n) gradient descent instead.
+          // True constraints are not supported so CTE is interpreted as pure equaves.
+          const temperEquaves =
+            options.value.temperEquaves && tempering.value !== "CTE";
+          const weights = options.value.weights;
+          const jip = subgroup.value.jip();
+          const commaMonzos = commas.value.map(
+            (comma) => subgroup.value.toMonzoAndResidual(comma)[0]
+          );
+          const mappingVector = vanishCommas(
+            commaMonzos,
+            jip,
+            weights,
+            temperEquaves
+          );
+          mapping = new Mapping(toPrimeMapping(mappingVector, subgroup.value));
+        } else {
+          mapping = Mapping.fromCommas(
+            commas.value,
+            DEFAULT_NUMBER_OF_COMPONENTS,
+            subgroup.value,
+            options.value
+          );
+        }
       }
       emit(
         "update:scale",
@@ -300,6 +345,7 @@ function modify() {
                 id="tempering-CTE"
                 value="CTE"
                 @focus="error = ''"
+                :disabled="constraintsDisabled"
                 v-model="tempering"
               />
               <label for="tempering-CTE"> CTE </label>
@@ -311,6 +357,7 @@ function modify() {
             <textarea
               id="constraints"
               @focus="error = ''"
+              :disabled="constraintsDisabled"
               v-model="constraintsString"
             ></textarea>
           </div>

src/constants.ts

@@ -16,3 +16,10 @@ export const LEFT_MOUSE_BTN = 0;
 
 // Offset such that default base MIDI note doesn't move in "simple" white mode.
 export const WHITE_MODE_OFFSET = 69 - 40;
+
+// === Sanity limits for tempering ===
+
+// Anything larger than this isn't evaluated interactively
+export const MAX_INTERACTIVE_SUBGROUP_SIZE = 6;
+// Anything larger than this uses O(n²) methods (if available) instead of O(exp(n))
+export const MAX_GEO_SUBGROUP_SIZE = 9;

src/tempering.ts

@@ -18,6 +18,18 @@ import {
 } from "xen-dev-utils";
 import { Interval, Scale } from "scale-workshop-core";
 
+export function toPrimeMapping(mapping: number[], subgroup: Subgroup) {
+  const result = subgroup.toPrimeMapping(mapping);
+
+  while (result.length > DEFAULT_NUMBER_OF_COMPONENTS) {
+    result.pop();
+  }
+  while (result.length < DEFAULT_NUMBER_OF_COMPONENTS) {
+    result.push(PRIME_CENTS[result.length]);
+  }
+  return result as number[];
+}
+
 export class Mapping {
   vector: number[];