Add and reschedule harris corner detector

apps/harris/Makefile

@@ -0,0 +1,27 @@
+include ../support/Makefile.inc
+
+all: $(BIN)/$(HL_TARGET)/filter
+
+test: $(BIN)/$(HL_TARGET)/out.png
+
+$(GENERATOR_BIN)/harris.generator: harris_generator.cpp $(GENERATOR_DEPS)
+	@mkdir -p $(@D)
+	$(CXX) $(CXXFLAGS) -g $(filter-out %.h,$^) -o $@ $(LDFLAGS) $(HALIDE_SYSTEM_LIBS) $(USE_EXPORT_DYNAMIC)
+
+$(BIN)/%/harris.a: $(GENERATOR_BIN)/harris.generator
+	@mkdir -p $(@D)
+	$< -g harris -f harris -o $(BIN)/$* target=$* auto_schedule=false
+
+$(BIN)/%/harris_auto_schedule.a: $(GENERATOR_BIN)/harris.generator
+	@mkdir -p $(@D)
+	$< -g harris -f harris_auto_schedule -o $(BIN)/$* target=$* auto_schedule=true 
+
+$(BIN)/%/filter: filter.cpp $(BIN)/%/harris.a $(BIN)/%/harris_auto_schedule.a
+	@mkdir -p $(@D)
+	$(CXX) $(CXXFLAGS) -I$(BIN)/$* -Wall -O3 $^ -o $@ $(LDFLAGS) $(IMAGE_IO_FLAGS) $(CUDA_LDFLAGS) $(OPENCL_LDFLAGS) $(OPENGL_LDFLAGS)
+
+$(BIN)/%/out.png: $(BIN)/%/filter
+	$< ../images/rgb.png $(BIN)/$*/out.png
+
+clean:
+	rm -rf $(BIN)

apps/harris/filter.cpp

@@ -0,0 +1,44 @@
+#include <cstdio>
+#include <cstdlib>
+#include <cassert>
+
+#include "HalideRuntime.h"
+#include "HalideBuffer.h"
+
+#include "harris.h"
+#include "harris_auto_schedule.h"
+
+#include "halide_benchmark.h"
+#include "halide_image_io.h"
+
+using namespace Halide::Tools;
+
+int main(int argc, char **argv) {
+    if (argc != 3) {
+        printf("Usage: %s in out\n", argv[0]);
+        return 1;
+    }
+
+    Halide::Runtime::Buffer<float> input = load_and_convert_image(argv[1]);
+
+    // The harris app doesn't use a boundary condition
+    Halide::Runtime::Buffer<float> output(input.width() - 6, input.height() - 6);
+    output.set_min(3, 3);
+
+
+    double best_manual = benchmark([&]() {
+        harris(input, output);
+        output.device_sync();
+    });
+    printf("Manually-tuned time: %gms\n", best_manual * 1e3);
+
+    double best_auto = benchmark([&]() {
+        harris_auto_schedule(input, output);
+        output.device_sync();
+    });
+    printf("Auto-scheduled time: %gms\n", best_auto * 1e3);
+
+    convert_and_save_image(output, argv[2]);
+
+    return 0;
+}

apps/harris/harris_generator.cpp

@@ -0,0 +1,97 @@
+#include "Halide.h"
+
+namespace {
+
+using namespace Halide;
+
+Expr sum3x3(Func f, Var x, Var y) {
+    return f(x-1, y-1) + f(x-1, y) + f(x-1, y+1) +
+           f(x, y-1)   + f(x, y)   + f(x, y+1) +
+           f(x+1, y-1) + f(x+1, y) + f(x+1, y+1);
+}
+
+class Harris : public Halide::Generator<Harris> {
+public:
+    Input<Buffer<float>>  input{"input", 3};
+    Output<Buffer<float>> output{"output", 2};
+
+    void generate() {
+        Var x("x"), y("y"), c("c");
+
+        // Algorithm
+        Func gray("gray");
+        gray(x, y) = (0.299f * input(x, y, 0) +
+                      0.587f * input(x, y, 1) +
+                      0.114f * input(x, y, 2));
+
+        Func Iy("Iy");
+        Iy(x, y) = gray(x-1, y-1)*(-1.0f/12) + gray(x-1, y+1)*(1.0f/12) +
+                   gray(x, y-1)*(-2.0f/12) + gray(x, y+1)*(2.0f/12) +
+                   gray(x+1, y-1)*(-1.0f/12) + gray(x+1, y+1)*(1.0f/12);
+
+        Func Ix("Ix");
+        Ix(x, y) = gray(x-1, y-1)*(-1.0f/12) + gray(x+1, y-1)*(1.0f/12) +
+                   gray(x-1, y)*(-2.0f/12) + gray(x+1, y)*(2.0f/12) +
+                   gray(x-1, y+1)*(-1.0f/12) + gray(x+1, y+1)*(1.0f/12);
+
+        Func Ixx("Ixx");
+        Ixx(x, y) = Ix(x, y) * Ix(x, y);
+
+        Func Iyy("Iyy");
+        Iyy(x, y) = Iy(x, y) * Iy(x, y);
+
+        Func Ixy("Ixy");
+        Ixy(x, y) = Ix(x, y) * Iy(x, y);
+
+        Func Sxx("Sxx");
+        Sxx(x, y) = sum3x3(Ixx, x, y);
+
+        Func Syy("Syy");
+        Syy(x, y) = sum3x3(Iyy, x, y);
+
+        Func Sxy("Sxy");
+        Sxy(x, y) = sum3x3(Ixy, x, y);
+
+        Func det("det");
+        det(x, y) = Sxx(x, y) * Syy(x, y) - Sxy(x, y) * Sxy(x, y);
+
+        Func trace("trace");
+        trace(x, y) = Sxx(x, y) + Syy(x, y);
+
+        output(x, y) = det(x, y) - 0.04f * trace(x, y) * trace(x, y);
+
+        // Estimates (for autoscheduler; ignored otherwise)
+        {
+            const int kWidth = 1536;
+            const int kHeight = 2560;
+            input.dim(0).set_estimate(0, kWidth)
+                 .dim(1).set_estimate(0, kHeight)
+                 .dim(2).set_estimate(0, 3);
+            output.dim(0).set_estimate(3, kWidth - 6)
+                  .dim(1).set_estimate(3, kHeight - 6);
+        }
+
+        // Schedule
+        if (!auto_schedule) {
+            Var xi("xi"), yi("yi");
+            if (get_target().has_gpu_feature()) {
+
+                output.gpu_tile(x, y, xi, yi, 30, 14);
+                Ix.compute_at(output, x).gpu_threads(x, y);
+                Iy.compute_at(output, x).gpu_threads(x, y);
+                Ix.compute_with(Iy, x);
+            } else {
+                const int vec = natural_vector_size<float>();
+                output.split(y, y, yi, 32).parallel(y).vectorize(x, vec);
+                gray.store_at(output, y).compute_at(output, yi).vectorize(x, vec);
+                Ix.store_at(output, y).compute_at(output, yi).vectorize(x, vec);
+                Iy.store_at(output, y).compute_at(output, yi).vectorize(x, vec);
+                Ix.compute_with(Iy, x);
+            }
+        }
+    }
+};
+
+}  // namespace
+
+HALIDE_REGISTER_GENERATOR(Harris, harris)