wgblas
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    Function isamax

    • Returns the 0-based index of the element with the largest absolute value. Ties are broken in favour of the lower index, matching CBLAS behaviour.

      import { init, cleanup } from "wgblas";
      import { isamax } from "wgblas/isamax";
      import { randomFloat32Array } from "wgblas/random";

      const device = await init();

      const n = 10;
      const x = randomFloat32Array(n, -10, 10);

      console.log("x:     ", x);
      const { index } = await isamax(device, n, x, 1);
      console.log("index: ", index);
      console.log("x[index]: ", x[index]);
      if (typeof process !== "undefined") cleanup();

      Browser (standalone HTML):

      <!doctype html>
      <html lang="en">
        <head>
          <meta charset="UTF-8" />
          <title>isamax — wgblas browser example</title>
          <script src="https://manit2004.github.io/wgblas/wgblas.browser.js"></script>
        </head>
        <body>
          <pre id="out">Running…</pre>
          <script>
            const { init, isamax, randomFloat32Array, cleanup } = window.wgblas;

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

              const n = 10;
              const x = randomFloat32Array(n, -10, 10);

              const { index } = await isamax(device, n, x, 1);

              document.getElementById("out").textContent =
                "x:        " + Array.from(x).map(v => v.toFixed(4)).join(", ") +
                "\nindex:    " + index +
                "\nx[index]: " + x[index].toFixed(4);

              cleanup();
            })();
          </script>
        </body>
      </html>

      Parameters

      • device: GPUDevice

        GPUDevice from init()

      • n: number

        number of elements (must be a positive integer)

      • x: Float32Array

        Float32Array input vector

      • incx: number

        stride for x (must be a positive integer)

      Returns Promise<{ index: number } | { gpuTimeMs: number; index: number }>

      0-based index of max |x[i]|

      Source code: isamax.mjs (L18)

    • Returns the 0-based index of the element with the largest absolute value. Ties are broken in favour of the lower index, matching CBLAS behaviour.

      import { init, cleanup } from "wgblas";
      import { isamax } from "wgblas/isamax";
      import { sscal } from "wgblas/sscal";
      import { GpuVector } from "wgblas/classes/GpuVector";
      import { randomFloat32Array } from "wgblas/random";

      const device = await init();

      const n = 10;
      const scale = 2.0;
      const x = randomFloat32Array(n, -10, 10);

      const xGpu = GpuVector.from(x);

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

      await sscal(device, n, scale, xGpu, 1);
      const { index } = await isamax(device, n, xGpu, 1);
      console.log("index (of 2x): ", index);

      xGpu.destroy();

      if (typeof process !== "undefined") cleanup();

      Parameters

      • device: GPUDevice

        GPUDevice from init()

      • n: number

        number of elements (must be a positive integer)

      • x: GpuVector

        GpuVector input vector

      • incx: number

        stride for x (must be a positive integer)

      Returns Promise<{ index: number } | { gpuTimeMs: number; index: number }>

      0-based index of max |x[i]|

      Source code: isamax.mjs (L18)

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