Question

我有以下CUDA内核，它执行广度优先搜索。

__global__ void bfs(const Edge* edges, int* vertices, int* current_depth, bool* done){

    int e = blockDim.x * blockIdx.x + threadIdx.x;
    int vfirst = edges[e].first;
    int dfirst = vertices[vfirst];
    int vsecond = edges[e].second;
    int dsecond = vertices[vsecond];

    if((dfirst == *current_depth) && (dsecond == -1)){
        vertices[vsecond] = dfirst +1;
        *current_depth = dfirst+1;
        *done = false;
    }
    if((dsecond == *current_depth) && (dfirst == -1)){
        vertices[vfirst] = dsecond + 1;
        *current_depth = dsecond +1;
        *done = false;
    }
}

此内核获取在主机上分配的值，然后在设备上进行修改并写回主机。

所以我宣布了两个变量并以这种方式将它们复制到设备

bool h_done = true;
    bool* d_done;
    int* d_current_depth;
    int h_current_depth = 0;

    cudaMalloc((void**)&d_done, sizeof(bool));
    cudaMalloc((void**)&d_current_depth, sizeof(int));
    cudaMemcpy(d_done, &h_done, sizeof(bool), cudaMemcpyHostToDevice);
    cudaMemcpy(d_current_depth, &h_current_depth, sizeof(int), cudaMemcpyHostDevice);

在这里循环启动内核。

bfs<<<blocksPerGrid, threadsPerBlock>>>(h_edges, h_vertices, d_current_depth, d_done);

代码编译并运行正常但主机值永远不会在设备上修改，反之亦然。我已经详细介绍了NVIDIA示例代码，但似乎无法做到这一点。我是CUDA的新手。任何帮助表示赞赏。

Answer 1

此：

import javafx.animation.Animation;
import javafx.animation.TranslateTransition;
import javafx.application.Application;
import javafx.beans.binding.Bindings;
import javafx.beans.binding.BooleanBinding;
import javafx.geometry.Point2D;
import javafx.scene.Scene;
import javafx.scene.input.KeyCode;
import javafx.scene.layout.Pane;
import javafx.scene.paint.Color;
import javafx.scene.shape.Circle;
import javafx.scene.shape.Line;
import javafx.scene.transform.Rotate;
import javafx.stage.Stage;
import javafx.util.Duration;

public class ShootingGame extends Application {

    @Override
    public void start(Stage primaryStage) {
        final double width = 400 ;
        final double height = 400 ;

        final double targetRadius = 25 ;
        final double projectileRadius = 5 ;

        final double weaponLength = 25 ;

        final double weaponX = width / 2 ;
        final double weaponStartY = height ;
        final double weaponEndY = height - weaponLength ;

        final double targetStartX = targetRadius ;
        final double targetY = targetRadius * 2 ;;

        Pane root = new Pane();
        Circle target = new Circle(targetStartX, targetY, targetRadius, Color.BLUE);
        TranslateTransition targetMotion = new TranslateTransition(Duration.seconds(2), target);
        targetMotion.setByX(350);
        targetMotion.setAutoReverse(true);
        targetMotion.setCycleCount(Animation.INDEFINITE);
        targetMotion.play();

        Line weapon = new Line(weaponX, weaponStartY, weaponX, weaponEndY);
        weapon.setStrokeWidth(5);
        Rotate weaponRotation = new Rotate(0, weaponX, weaponStartY);
        weapon.getTransforms().add(weaponRotation);

        Scene scene = new Scene(root, width, height);
        scene.setOnKeyPressed(e -> {
            if (e.getCode() == KeyCode.LEFT) {
                weaponRotation.setAngle(Math.max(-45, weaponRotation.getAngle() - 2));
            }
            if (e.getCode() == KeyCode.RIGHT) {
                weaponRotation.setAngle(Math.min(45, weaponRotation.getAngle() + 2));
            }
            if (e.getCode() == KeyCode.SPACE) {

                Point2D weaponEnd = weapon.localToParent(weaponX, weaponEndY);

                Circle projectile = new Circle(weaponEnd.getX(), weaponEnd.getY(), projectileRadius);

                TranslateTransition shot = new TranslateTransition(Duration.seconds(1), projectile);
                shot.setByX(Math.tan(Math.toRadians(weaponRotation.getAngle())) * height);
                shot.setByY(-height);
                shot.setOnFinished(event -> root.getChildren().remove(projectile));

                BooleanBinding hit = Bindings.createBooleanBinding(() -> {
                    Point2D targetLocation = target.localToParent(targetStartX, targetY);
                    Point2D projectileLocation = projectile.localToParent(weaponEnd);
                    return (targetLocation.distance(projectileLocation) < targetRadius + projectileRadius) ;
                }, projectile.translateXProperty(), projectile.translateYProperty());

                hit.addListener((obs, wasHit, isNowHit) -> {
                    if (isNowHit) {
                        System.out.println("Hit");
                        root.getChildren().remove(projectile);
                        root.getChildren().remove(target);
                        targetMotion.stop();
                        shot.stop();
                    }
                });

                root.getChildren().add(projectile);
                shot.play();
            }
        });

        root.getChildren().addAll(target, weapon);

        primaryStage.setScene(scene);
        primaryStage.show();
    }

    public static void main(String[] args) {
        launch(args);
    }
}

几乎肯定是错的。

除非您使用托管内存（我怀疑），bfs<<<blocksPerGrid, threadsPerBlock>>>(h_edges, h_vertices, d_current_depth, d_done);和h_edges在主机内存中（以其名称命名）变量。您无法在设备代码中传递和修改常规主机指针。由于这个错误，你的内核很可能无法运行。

您的代码报告的未指定的启动错误很可能是由此造成的。

在CUDA中在主机和设备之间传递变量

1 个答案: