TensorFlow使用记录 (二）： 理解tf.nn.conv2d方法

2022-03-09

tf.nn.(输入, , , , =True, =”NHWC”, =[1,1,1,1], name=None)

参数：具体实现

输入形状：[batch, , , ]

形状：[, , , ]

计算过程：

1.将展开为 2-,shape: [**, ]

2.从输入中提取，形成一个，形状：[batch, , , **]

3.对于每个补丁，在右边乘以 1。即[batch, , , **] x [​​* * , ]，那么输出shape：[batch, , , ]

[注意：必须有 [0] = [3] = 1]。在大多数情况下，水平与垂直相同，即 = [1, , , 1]。

输出结果的形状计算：

在caffe里是这样的：

=floor(+2*pad-)/+1;向下取整

=地板(+2*pad-)/+1

它看起来像这样：

“相同”类型：

= ceil(/[1]); ceil 向上取整

= ceil(/[2])

“有效”类型：

= ceil(( – + 1) / [1])

= ceil(( – + 1) / [2])

验证码

# -*- coding:utf-8 -*-
from __future__ import division
import tensorflow as tf
import numpy as np
import math
import pandas as pd
input_arr = np.zeros((12, 15), dtype=np.float32)

number = 0
for row_idx in range(input_arr.shape[0]):
    for col_idx in range(input_arr.shape[1]):
        input_arr[row_idx][col_idx] = number
        number +=1
number = 6
w_arr = np.zeros((2, 3), dtype=np.float32)
for row_idx in range(w_arr.shape[0]):
    for col_idx in range(w_arr.shape[1]):
        w_arr[row_idx][col_idx] = number
        number += 1
stride = [1, 1, 1, 1]

# 从卷积的定义【实际上不是卷积，而是cross-correlation】进行计算验证---对VALID类型卷积进行
res_shape_h = int(math.ceil((input_arr.shape[0] - w_arr.shape[0] + 1) / stride[1]))
res_shape_w = int(math.ceil(input_arr.shape[1] - w_arr.shape[1] + 1) / stride[2])
validation_res = np.zeros(shape=(res_shape_h, res_shape_w), dtype=np.float32)
for row_idx in range(validation_res.shape[0]):
    for col_idx in range(validation_res.shape[1]):
        patch = input_arr[row_idx : row_idx+w_arr.shape[0], col_idx : col_idx+w_arr.shape[1]]
        # 这里的 * 实际上代表的是点积，即对应元素位置相乘
        res = np.sum(patch * w_arr)
        validation_res[row_idx][col_idx] = res
print('result of convolution from its definition: validation_res')
print(validation_res)
pd.DataFrame(validation_res).to_csv('validation_res.csv', index = False, header=False)

# 从TensorFlow实现出发
input_arr = np.reshape(input_arr, [1, input_arr.shape[0], input_arr.shape[1], 1])
w_arr = np.reshape(w_arr, [w_arr.shape[0], w_arr.shape[1], 1, 1])
# 输入Tensor, shape: [1, 12, 15, 1]
net_in = tf.constant(value=input_arr, dtype=tf.float32)
# filter, shape: [2, 3, 1, 1]
W = tf.constant(value=w_arr, dtype=tf.float32)
# TensorFlow卷积的计算结果
# valid卷积结果, shape: [1, 11, 13, 1]
result_conv_valid = tf.nn.conv2d(net_in, W, stride, 'VALID')
# same卷积结果, shape: [1, 12, 15, 1]

result_conv_smae = tf.nn.conv2d(net_in, W, stride, 'SAME')
with tf.Session() as sess:
    sess.run(tf.global_variables_initializer())
    valid_conv_res, same_conv_res = sess.run([result_conv_valid, result_conv_smae])
print(valid_conv_res.shape)
valid_conv_res = np.reshape(valid_conv_res, [valid_conv_res.shape[1], valid_conv_res.shape[2]])
same_conv_res = np.reshape(same_conv_res, [same_conv_res.shape[1], same_conv_res.shape[2]])
print('TensorFlow con res: valid_conv_res')
print(valid_conv_res)
pd.DataFrame(valid_conv_res).to_csv('conv_res.csv', index=False, header=False)
pd.DataFrame(same_conv_res).to_csv('same_res.csv', index=False, header=False)

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