Question

我想将一个形状(..., n * (n - 1) / 2)的数组打包到张量的下三角部分，其形状为(..., n, n)，其中...表示任意形状。在numpy中，我会将其实现为

import numpy as np

# Create the array to store data in
arbitrary_shape = (10, 11, 12)
n = 5
target = np.zeros(arbitrary_shape + (n, n))
# Create the source array
source = np.random.normal(0, 1, arbitrary_shape + (n * (n - 1) / 2,))
# Create indices and set values
u, v = np.tril_indices(n, -1)
target[..., u, v] = source
# Check that everything went ok
print target[0, 0, 0]

到目前为止，我已经能够使用transpose，reshape和scatter_update的组合在tensorflow中实现类似的功能，但感觉很笨拙。

import tensorflow as tf

# Create the source array
source = np.random.normal(0, 1, (n * (n - 1) / 2,) + arbitrary_shape)

sess = tf.InteractiveSession()

# Create a flattened representation
target = tf.Variable(np.zeros((n * n,) + arbitrary_shape))
# Assign the values
target = tf.scatter_update(target, u * n + v, source)
# Reorder the axes and reshape into a square matrix along the last dimension
target = tf.transpose(target, (1, 2, 3, 0))
target = tf.reshape(target, arbitrary_shape + (n, n))

# Initialise variables and check results
sess.run(tf.initialize_all_variables())
print target.eval()[0, 0, 0]

sess.close()

有没有更好的方法来实现这一目标？

Answer 1

我意识到这有点晚了，但我一直试图加载一个较低的三角矩阵，并且我使用sparse_to_dense工作了：

class ExerciseDatabaseController: UIViewController, UITableViewDataSource, UITableViewDelegate {

@IBOutlet weak var ExerciseSearchField: UISearchBar!
@IBOutlet weak var ExercisesTableView: UITableView!

var arrRes = [[String:AnyObject]]() // Array of dictionary

override func viewDidLoad() {
    super.viewDidLoad()

    let arrRes = ApiService.getExerciseData()

    if let resData = ApiService.swiftyJsonVar?["exercise"].arrayObject {
        self.arrRes = resData as! [[String:AnyObject]]
    }
    if self.arrRes.count > 0 {
        self.ExercisesTableView.reloadData()
    }

    print(arrRes)
    // Do any additional setup after loading the view.
}

func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
    return arrRes.count
}

func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
    let cell = tableView.dequeueReusableCell(withIdentifier: "Cell", for: indexPath)
    var dict = arrRes[indexPath.row]
    cell.textLabel?.text = dict["name"] as? String
    cell.detailTextLabel?.text = dict["description"] as? String
    return cell
}

Answer 2

您可以使用fill_lower_triangular：

执行此操作

import numpy as np
import tensorflow as tf
from tensorflow.python.ops.distributions.util import fill_lower_triangular
n = 4
coeffs = tf.constant(np.random.normal(0, 1, int(n*(n+1)/2)), dtype=tf.float64)
lower_diag = fill_lower_triangular(coeffs)

将阵列打包成张量的下三角形

2 个答案: