以PLOT3D格式保存点云

Question

我有以下函数以PLOT3D格式保存点云：

def write(filename, mesh):
    """
    Write the mesh to filename in PLOT3D format.
    filename: is the name of the output file.
    mesh: is a numpy array of size (N,2) or (N, 3) where N is the number of points. mesh[i] is a numpy array coordinates of the i'th point.

    """
    points = mesh.points
    imax = np.unique(points[:, 0]).size
    jmax = np.unique(points[:, 1]).size

    _2d = False
    if points.shape[1] == 2:
        _2d = True
    elif np.unique(points[:, 2]).size == 1:
        _2d = True

    with open(filename, "w") as p3dfile:
        if not _2d:
            kmax = np.unique(points[:, 2]).size
            print(imax, jmax, kmax, file=p3dfile)
            for value in points.flatten(order="F"):
                print(value, file=p3dfile)
        else:
            print(imax, jmax, file=p3dfile)
            for value in points[:, 0:2].flatten(order="F"):
                print(value, file=p3dfile)

对于大量的点，这个函数非常慢。

我很感激任何关于改进上述代码的建议。

Answer 1

Optimizations/improvements:

表名

• 对于特定函数来说，write太泛型了。更好的名字之一是write_points
• _2d。即使变量被标记为“受保护的”_...，以数字开头的名称也是错误的命名模式。因为它是布尔标志，所以有意义的名称应该是is_2dim (是二维空间)

由于mesh参数只用于访问其内部属性points，所以最好直接传递目标点数据结构(称为参数替换查询)。

在当前的方法中，当到达条件if not _2d:时，将重复计算表达式np.unique(points[:, 2]).size，而不是：

由于points数组应该是带有2或3列的2d数组，所以我们可以一次收集所有列的唯一计数(而不是声明imax，jmax)：

col_counts = [np.unique(row).size for row in points.T]

整个条件：

_2d = False
if points.shape[1] == 2:
    _2d = True
elif np.unique(points[:, 2]).size == 1:
    _2d = True

现在替换为一条语句：

is_2dim = points.shape[1] == 2 or col_counts[2] == 1

在每次迭代时调用print函数将数据写入文件：

for value in points.flatten(order="F"):
    print(value, file=p3dfile)

与立即调用生成器表达式上的书面()相比，它的效率和性能肯定更低。

最后优化的函数：

def write_points(filename, points):
    """
    Write the mesh points to filename in PLOT3D format.
    filename: is the name of the output file.
    mesh: is a numpy array of size (N,2) or (N, 3) where N is the number of points. mesh[i] is a numpy array coordinates of the i'th point.

    """
    col_counts = [np.unique(row).size for row in points.T]
    is_2dim = points.shape[1] == 2 or col_counts[2] == 1

    with open(filename, "w") as p3dfile:
        pd3file.write(' '.join(map(str, col_counts)))
        pd3file.writelines(f'{num}\n' for num in points.flatten(order="F"))