DSL kernel

[FrancescAlted]

This allows to use a bespoke DSL (Domain Specific Language) for expressing computational kernels on blocks that are beyond single expressions. For example:

@blosc2.dsl_kernel
def mandelbrot_dsl(cr, ci, max_iter):
    # max_iter is passed per-call through lazyudf inputs
    zr = 0.0
    zi = 0.0
    escape_iter = float(max_iter)
    for it in range(max_iter):
        zr2 = zr * zr
        zi2 = zi * zi
        mag2 = zr2 + zi2

        active = escape_iter == float(max_iter)
        just_escaped = (mag2 > 4.0) & active
        escape_iter = np.where(just_escaped, it, escape_iter)

        active = escape_iter == float(max_iter)
        if np.all(active == 0):
            break

        zr_new = zr2 - zi2 + cr
        zi_new = 2.0 * zr * zi + ci
        zr = np.where(active, zr_new, zr)
        zi = np.where(active, zi_new, zi)

    return escape_iter

See full example in: https://github.com/Blosc/python-blosc2/blob/3590e61b33e75a8dde77bf8c54c2d5f1faa31746/examples/ndarray/mandelbrot-dsl.ipynb