go语言中for _,vv := range语句用法
时间: 2024-02-22 14:55:45 浏览: 21
`for _, vv := range` 语句用于遍历一个集合类型(如数组、切片、映射、字符串等),并且不需要使用集合中的索引值。
具体语法如下:
```go
for _, vv := range collection {
// ...
}
```
其中,`_` 表示忽略集合中的索引值,`vv` 表示当前遍历到的元素值。
例如,遍历一个切片并打印其中的元素:
```go
package main
import "fmt"
func main() {
s := []int{1, 2, 3}
for _, v := range s {
fmt.Println(v)
}
}
```
输出:
```
1
2
3
```
需要注意的是,如果集合类型中元素的类型是指针类型,那么遍历时得到的将是指针的副本,而不是原始指针。如果需要修改原始指针指向的值,需要使用集合中元素的原始变量名。
相关问题
代码time_start = time.time() results = list() iterations = 2001 lr = 1e-2 model = func_critic_model(input_shape=(None, train_img.shape[1]), act_func='relu') loss_func = tf.keras.losses.MeanSquaredError() alg = "gd" # alg = "gd" for kk in range(iterations): with tf.GradientTape() as tape: predict_label = model(train_img) loss_val = loss_func(predict_label, train_lbl) grads = tape.gradient(loss_val, model.trainable_variables) overall_grad = tf.concat([tf.reshape(grad, -1) for grad in grads], 0) overall_model = tf.concat([tf.reshape(weight, -1) for weight in model.weights], 0) overall_grad = overall_grad + 0.001 * overall_model ## adding a regularization term results.append(loss_val.numpy()) if alg == 'gd': overall_model -= lr * overall_grad ### gradient descent elif alg == 'gdn': ## gradient descent with nestrov's momentum overall_vv_new = overall_model - lr * overall_grad overall_model = (1 + gamma) * oerall_vv_new - gamma * overall_vv overall_vv = overall_new pass model_start = 0 for idx, weight in enumerate(model.weights): model_end = model_start + tf.size(weight) weight.assign(tf.reshape()) for grad, ww in zip(grads, model.weights): ww.assign(ww - lr * grad) if kk % 100 == 0: print(f"Iter: {kk}, loss: {loss_val:.3f}, Duration: {time.time() - time_start:.3f} sec...") input_shape = train_img.shape[1] - 1 model = tf.keras.Sequential([ tf.keras.layers.Input(shape=(input_shape,)), tf.keras.layers.Dense(30, activation="relu"), tf.keras.layers.Dense(20, activation="relu"), tf.keras.layers.Dense(1) ]) n_epochs = 20 batch_size = 100 learning_rate = 0.01 momentum = 0.9 sgd_optimizer = tf.keras.optimizers.SGD(learning_rate=learning_rate, momentum=momentum) model.compile(loss="mean_squared_error", optimizer=sgd_optimizer) history = model.fit(train_img, train_lbl, epochs=n_epochs, batch_size=batch_size, validation_data=(test_img, test_lbl)) nag_optimizer = tf.keras.optimizers.SGD(learning_rate=learning_rate, momentum=momentum, nesterov=True) model.compile(loss="mean_squared_error", optimizer=nag_optimizer) history = model.fit(train_img, train_lbl, epochs=n_epochs, batch_size=batch_size, validation_data=(test_img, test_lbl))运行后报错TypeError: Missing required positional argument,如何改正
这个错误信息并没有指明是哪个函数缺少了必要的位置参数,因此需要仔细检查代码。根据代码的结构,可能是在使用`tf.reshape()`函数时缺少了必要的参数。
具体来说,下面这行代码中出现了这个错误:
```
weight.assign(tf.reshape())
```
`tf.reshape()`函数需要传入两个必要的参数:`tensor`和`shape`。因此,你需要指定这个函数的第一个参数`tensor`,也就是`weight`,以及希望将其reshape成的新形状`shape`。例如,如果你希望将`weight`变成一个形状为`(batch_size, input_shape)`的张量,可以这样写:
```
weight.assign(tf.reshape(weight, (batch_size, input_shape)))
```
请根据你的实际需求修改这行代码,确保`tf.reshape()`函数的两个参数都被正确地指定。
将下列代码改为vs内可运行的代码:float smoothCot() { float err = -1; cogs.clear(); v_end = mesh.vertices_end(); // for (v_it = mesh.vertices_begin(); v_it != v_end; ++v_it) { cog[0] = cog[1] = cog[2] = valence = 0.0; for (vv_it = mesh.vv_iter(*v_it); vv_it.is_valid(); ++vv_it) { double cot_weight = 0.0; MyMesh::HalfedgeHandle heh = mesh.find_halfedge(*v_it, *vv_it); if (!mesh.is_boundary(heh)) { MyMesh::HalfedgeHandle prev_heh = mesh.prev_halfedge_handle(heh); MyMesh::HalfedgeHandle next_heh = mesh.next_halfedge_handle(heh); MyMesh::VertexHandle prev_vh = mesh.to_vertex_handle(prev_heh); MyMesh::VertexHandle next_vh = mesh.to_vertex_handle(next_heh); MyMesh::Point prev_p = mesh.point(prev_vh); MyMesh::Point curr_p = mesh.point(*v_it); MyMesh::Point next_p = mesh.point(next_vh); double cot_alpha = cot(prev_p - curr_p, next_p - curr_p); double cot_beta = cot(curr_p - prev_p, next_p - prev_p); cot_weight = cot_alpha + cot_beta; } cog += cot_weight * mesh.point(*vv_it); valence += cot_weight; } cogs.push_back(cog / valence); } for (v_it = mesh.vertices_begin(), cog_it = cogs.begin(); v_it != v_end; ++v_it, ++cog_it) { if (!mesh.is_boundary(*v_it)) { MyMesh::Point p = mesh.point(*v_it); err = max(err, (p - *cog_it).norm()); mesh.set_point(*v_it, *cog_it); } } return err; }
请注意,代码中使用了 MyMesh 类型,需要先定义和引入该类型,以下是修改后的可运行代码:
```c++
#include <OpenMesh/Core/IO/MeshIO.hh>
#include <OpenMesh/Core/Mesh/TriMesh_ArrayKernelT.hh>
#include <vector>
typedef OpenMesh::TriMesh_ArrayKernelT<> MyMesh;
float smoothCot(MyMesh& mesh) {
float err = -1;
std::vector<MyMesh::Point> cogs;
cogs.reserve(mesh.n_vertices());
MyMesh::VertexIter v_it, v_end;
MyMesh::VertexVertexIter vv_it;
MyMesh::Point cog;
double valence;
v_end = mesh.vertices_end();
for (v_it = mesh.vertices_begin(); v_it != v_end; ++v_it) {
cog[0] = cog[1] = cog[2] = valence = 0.0;
for (vv_it = mesh.vv_iter(*v_it); vv_it.is_valid(); ++vv_it) {
double cot_weight = 0.0;
MyMesh::HalfedgeHandle heh = mesh.find_halfedge(*v_it, *vv_it);
if (!mesh.is_boundary(heh)) {
MyMesh::HalfedgeHandle prev_heh = mesh.prev_halfedge_handle(heh);
MyMesh::HalfedgeHandle next_heh = mesh.next_halfedge_handle(heh);
MyMesh::VertexHandle prev_vh = mesh.to_vertex_handle(prev_heh);
MyMesh::VertexHandle next_vh = mesh.to_vertex_handle(next_heh);
MyMesh::Point prev_p = mesh.point(prev_vh);
MyMesh::Point curr_p = mesh.point(*v_it);
MyMesh::Point next_p = mesh.point(next_vh);
double cot_alpha = cot(prev_p - curr_p, next_p - curr_p);
double cot_beta = cot(curr_p - prev_p, next_p - prev_p);
cot_weight = cot_alpha + cot_beta;
}
cog += cot_weight * mesh.point(*vv_it);
valence += cot_weight;
}
cogs.push_back(cog / valence);
}
std::vector<MyMesh::Point>::iterator cog_it = cogs.begin();
for (v_it = mesh.vertices_begin(); v_it != v_end; ++v_it, ++cog_it) {
if (!mesh.is_boundary(*v_it)) {
MyMesh::Point p = mesh.point(*v_it);
err = std::max(err, (p - *cog_it).norm());
mesh.set_point(*v_it, *cog_it);
}
}
return err;
}
int main(int argc, char **argv) {
MyMesh mesh;
if (!OpenMesh::IO::read_mesh(mesh, argv[1])) {
std::cerr << "read error\n";
return 1;
}
std::cout << "smoothCot error: " << smoothCot(mesh) << std::endl;
if (!OpenMesh::IO::write_mesh(mesh, "output.obj")) {
std::cerr << "write error\n";
return 1;
}
return 0;
}
```
其中,cot 函数需要自己实现,如下:
```c++
double cot(const MyMesh::Point& v1, const MyMesh::Point& v2) {
return std::tan(MyMesh::Angle(v1, v2));
}
```
请注意,以上代码仅供参考,可能存在错误或不足之处,需要结合具体情况进行修改和完善。