bounds_inference_rdom.cpp

#include "Halide.h"
#include <stdio.h>

/*
   Bounds inference bug?

   Two versions of the same accumulation, one uses RDom the other defines a chain of Funcs.

   Compile and run with -DUSE_RDOM=0 and it reports:

        input: -2 -2 104 104
          dir: -1 -1 102 102

    But compile and run with -DUSE_RDOM=1 and it fails:

        Error at bounds_inference_rdom.cpp:46:
        Buffer dir may be accessed in an unbounded way in dimension 0
*/

using namespace Halide;

int main(int argc, char **argv) {
    ImageParam input(Float(32), 2, "input");
    ImageParam dir(Float(32), 3, "dir");

    Var x, y, d;

    Func cdir("cdir");
    cdir(x, y, d) = clamp(dir(x, y, d), -1.0f, 1.0f);

    Func output("output");

// Tuple structure accessors
#define S_VAL(t) (t)[0]
#define S_X(t)   (t)[1]
#define S_Y(t)   (t)[2]
    Tuple start = Tuple(0.0f, cast<float>(x), cast<float>(y));

// Get next tuple from this tuple
#define STEP(t) Tuple( \
        input(cast<int>(S_X(t)), cast<int>(S_Y(t))), \
        S_X(t) + cdir(cast<int>(S_X(t)), cast<int>(S_Y(t)), 0), \
        S_Y(t) + cdir(cast<int>(S_X(t)), cast<int>(S_Y(t)), 1) \
        )

#if USE_RDOM
    Var j;
    Func f("f");
    RDom r(1, 3, "r");
    f(j, x, y) = start;
    f(r, x, y) = STEP(f(r-1, x, y));
    output(x, y) = sum(S_VAL(f(r, x, y)));
#else
    Func f0("f0"), f1("f1"), f2("f2"), f3("f3");
    f0(x, y) = start;
    f1(x, y) = STEP(f0(x, y));
    f2(x, y) = STEP(f1(x, y));
    f3(x, y) = STEP(f2(x, y));
    output(x, y) = S_VAL(f0(x, y)) + S_VAL(f1(x, y)) + S_VAL(f2(x, y)) + S_VAL(f3(x, y));
#endif

    output.infer_input_bounds(100, 100);
    printf("input: %d %d %d %d\n", input.get().left(), input.get().top(), input.get().width(), input.get().height());
    printf("  dir: %d %d %d %d\n", dir.get().left(), dir.get().top(), dir.get().width(), dir.get().height());
}