Function dscal

Scales a double-precision vector by a constant: $$x \leftarrow \alpha x$$

x and alpha are each split into a (hi, lo) double-double f32 pair (see splitDoubleDouble/f64.mjs) since WGSL has no f64 type; the multiply uses Dekker's double-double algorithm (see shaders/f64/), giving ~48 bits of mantissa — more than a single f32 (24 bits) but less than true f64 (52 bits), so results are not bit-exact with a CPU double.

import { init, cleanup } from "wgblas";
import { dscal } from "wgblas/dscal";

const device = await init();

const n = 5;
const alpha = 3;
const x = new Float64Array([1, 2, 3, 4, 5]);

console.log("before:", x);
const { x: result } = await dscal(device, n, alpha, x, 1);
console.log("after: ", result);
if (typeof process !== "undefined") cleanup();
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Browser (standalone HTML):

<!doctype html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <title>dscal — wgblas browser example</title>
    <script src="https://unpkg.com/wgblas/dist/wgblas.browser.js"></script>
  </head>
  <body>
    <pre id="out">Running…</pre>
    <script>
      const { init, dscal, cleanup } = window.wgblas;

      (async () => {
        const device = await init();

        const n = 5;
        const alpha = 3;
        const x = new Float64Array([1, 2, 3, 4, 5]);

        console.log("before:", x);
        const { x: result } = await dscal(device, n, alpha, x, 1);
        console.log("after: ", result);

        document.getElementById("out").textContent =
          "before: " + Array.from(x).map(v => v.toFixed(4)).join(", ") +
          "\nafter:  " + Array.from(result).map(v => v.toFixed(4)).join(", ");

        cleanup();
      })();
    </script>
  </body>
</html>
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Scales a double-precision vector by a constant: $$x \leftarrow \alpha x$$

import { init, cleanup } from "wgblas";
import { dscal } from "wgblas/dscal";
import { GpuVector } from "wgblas/classes/GpuVector";

const device = await init();

const n = 5;
const alpha = 3;
const x = new Float64Array([1, 2, 3, 4, 5]);

const xGpu = GpuVector.from(x);

console.log("x:     ", x);

await dscal(device, n, alpha, xGpu, 1);

const result = await xGpu.read();
console.log("result:", result);

xGpu.destroy();
if (typeof process !== "undefined") cleanup();
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