performance tips for computations on an ESP32

I looked into the mentioned sections but did not find anything applicable.

Just to stop being abstract: here is my code for the MDBT42Q

  let Neopixel = require("neopixel");

  let DisplaySize = 16*16;
  let Display     = new Uint8ClampedArray(DisplaySize*3);

  let PixelOffset = new Int16Array(256);
    for (let i = 0; i < 16; i++) {
      for (let j = 0; j < 16; j++) {
        let Index = i*16 + j;
        if (i % 2 === 0) {
          PixelOffset[Index] = Index*3;
        } else {
          PixelOffset[Index] = (i*16 + 15 - j)*3;
        }
      }
    }

  let normalized = new Uint8ClampedArray(16*16);
    for (let i = 0; i < 256; i++) {
      normalized[i] = (
        i === 0
        ? 0
        : Math.round(1 + 256/4*(i/256)*(i/256))
      );
    }

  let TemperatureMap = new Uint8ClampedArray(DisplaySize);
    for (let i = 0; i < 256; i++) {
      TemperatureMap[i] = 0;
    }

  let ColorMap = new Array(16);
    for (let i = 0; i < 16; i++) {
      ColorMap[i] = E.HSBtoRGB(i/16, 1, 1, true);
    }

/**** processNextFrame ****/

  let HeatX     = Math.round(16*Math.random()); // where to insert new intensity
  let HeatCount = Math.round(12*Math.random());        // how long to heat there

  let normalizedRGB = new Uint8ClampedArray(3);    // used by "processNextFrame"

  function processNextFrame () { "compiled";
    let i,j,k,l;
    for (i = 15; i > 0; i--) {             // intensity diffusion for upper rows
      k = i*16;
      TemperatureMap[k] = Math.round((
        6*TemperatureMap[k] + 2*TemperatureMap[k-16] + TemperatureMap[k-15]
      )/9);

      for (j = 1; j < 15; j++) {
        k++;
        TemperatureMap[k] = Math.round((
          6*TemperatureMap[k] +
          TemperatureMap[k-17] + 2*TemperatureMap[k-16] + TemperatureMap[k-15]
        )/10);
      }

      k++;
      TemperatureMap[k] = Math.round((
        6*TemperatureMap[k] + TemperatureMap[k-17] + 2*TemperatureMap[k-16]
      )/9);
    }

  /**** heat around HeatX, cool elsewhere ****/

    HeatCount -= 1;
    if (HeatCount < 0) {
      HeatX     = Math.round(16*Math.random());
      HeatCount = Math.round(12*Math.random());
    }

    l = HeatX-4;
    for (i = 0 /*, l = HeatX-4*/; i < l; i++) {
      TemperatureMap[i] = TemperatureMap[i] - 8;            // exploits clamping
    }
      i = HeatX-4;
      i++; if (i >= 0) { TemperatureMap[i] = TemperatureMap[i] + 2; }    // dto.
      i++; if (i >= 0) { TemperatureMap[i] = TemperatureMap[i] + 5; }    // dto.
      i++; if (i >= 0) { TemperatureMap[i] = TemperatureMap[i] + 7; }    // dto.
      i++;               TemperatureMap[i] = TemperatureMap[i] + 8;      // dto.
      i++; if (i < 16) { TemperatureMap[i] = TemperatureMap[i] + 7; }    // dto.
      i++; if (i < 16) { TemperatureMap[i] = TemperatureMap[i] + 5; }    // dto.
      i++; if (i < 16) { TemperatureMap[i] = TemperatureMap[i] + 2; }    // dto.
      i++;
    for (; i < 16; i++) {
      TemperatureMap[i] = TemperatureMap[i] - 8;            // exploits clamping
    }

  /**** prepare display ****/

    let RGB /*, normalizedRGB = new Uint8ClampedArray(3)*/;
    let RowStart, RowEnd;
    for (i = 0; i < 16; i++) {                                       // row-wise
      RowStart = i*16; RowEnd = RowStart + 15;
      for (j = 0, k = RowStart; j < 16; j++, k++) {               // column-wise
        RGB         = ColorMap[j];
        Temperature = TemperatureMap[k];
          if (Temperature < 16) {
            Temperature = 0;
          } else {
            Temperature = Math.max(48,Temperature)/256;
          }

        normalizedRGB[0] = normalized[Math.round(RGB[1]*Temperature)];
        normalizedRGB[1] = normalized[Math.round(RGB[0]*Temperature)];
        normalizedRGB[2] = normalized[Math.round(RGB[2]*Temperature)];

        Display.set(normalizedRGB, PixelOffset[k]);
      }
    }

  /**** show display ****/

    Neopixel.write(D22,Display);

  /**** wait for next frame and proceed ****/

let now = Date.now();
if (Timestamp > 0) { print(now-Timestamp); }
Timestamp = now;

    setTimeout(processNextFrame,0);
  }

let Timestamp = 0;
  setTimeout(processNextFrame,100);       // give Espruino some time to start up

it runs even without an attached Neopixel matrix display - but having one is far more impressive...