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#include "Halide.h"
using namespace Halide;
class Sobel : public Generator<Sobel> {
public:
Input<Buffer<uint8_t, 2>> input{"input"};
Output<Buffer<uint8_t, 2>> output{"output"};
GeneratorParam<bool> use_parallel_sched{"use_parallel_sched", true};
GeneratorParam<bool> use_prefetch_sched{"use_prefetch_sched", true};
void generate() {
bounded_input(x, y) = BoundaryConditions::repeat_edge(input)(x, y);
Func input_16{"input_16"};
input_16(x, y) = cast<uint16_t>(bounded_input(x, y));
sobel_x_avg(x, y) = input_16(x - 1, y) + 2 * input_16(x, y) + input_16(x + 1, y);
sobel_x(x, y) = absd(sobel_x_avg(x, y - 1), sobel_x_avg(x, y + 1));
sobel_y_avg(x, y) = input_16(x, y - 1) + 2 * input_16(x, y) + input_16(x, y + 1);
sobel_y(x, y) = absd(sobel_y_avg(x - 1, y), sobel_y_avg(x + 1, y));
// This sobel implementation is non-standard in that it doesn't take the square root
// of the gradient.
output(x, y) = cast<uint8_t>(clamp(sobel_x(x, y) + sobel_y(x, y), 0, 255));
}
void schedule() {
Var xi{"xi"}, yi{"yi"};
input.dim(0).set_min(0);
input.dim(1).set_min(0);
if (get_target().has_feature(Target::HVX)) {
const int vector_size = 128;
Expr input_stride = input.dim(1).stride();
input.dim(1).set_stride((input_stride / vector_size) * vector_size);
Expr output_stride = output.dim(1).stride();
output.dim(1).set_stride((output_stride / vector_size) * vector_size);
bounded_input
.compute_at(Func(output), y)
.align_storage(x, 128)
.vectorize(x, vector_size, TailStrategy::RoundUp);
output
.hexagon()
.tile(x, y, xi, yi, vector_size, 4, TailStrategy::RoundUp)
.vectorize(xi)
.unroll(yi);
if (use_prefetch_sched) {
output.prefetch(input, y, y, 2);
}
if (use_parallel_sched) {
Var yo;
output.split(y, yo, y, 128).parallel(yo);
}
} else {
const int vector_size = natural_vector_size<uint8_t>();
output
.vectorize(x, vector_size)
.parallel(y, 16);
}
}
private:
Var x{"x"}, y{"y"};
Func sobel_x_avg{"sobel_x_avg"}, sobel_y_avg{"sobel_y_avg"};
Func sobel_x{"sobel_x"}, sobel_y{"sobel_y"};
Func bounded_input{"bounded_input"};
};
HALIDE_REGISTER_GENERATOR(Sobel, sobel)
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