LSTM in PyTorch

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*Memos:

• My post explains LSTM layer.
• My post explains RNN().
• My post explains GRU().
• My post explains manual_seed().
• My post explains requires_grad.

LSTM() can get the three 2D or 3D tensors of the one or more elements computed by LSTM from the 2D or 3D tensor of zero or more elements as shown below:

*Memos:

• The 1st argument for initialization is input_size(Required-Type:int). *It must be 0 <= x.
• The 2nd argument for initialization is hidden_size(Required-Type:int). *It must be 1 <= x.
• The 3rd argument for initialization is num_layers(Optional-Default:1-Type:int): *Memos:
  • It must be 1 <= x.
  • It must be 1 < x, if dropout is 0 < x.
  • Its number is same as the number of bias_ih_lx, bias_ih_lx_reverse, bias_hh_lx, bias_hh_lx_reverse, weight_ih_lx, weight_ih_lx_reverse, weight_hh_lx and weight_hh_lx_reverse so if it's 3, there are bias_ih_l0, bias_ih_l1, bias_ih_l2, bias_ih_l0_reverse, bias_ih_l1_reverse, bias_ih_l2_reverse, bias_hh_l0, bias_hh_l1 etc.
• The 4th argument for initialization is bias(Optional-Default:True-Type:bool). *My post explains bias argument.
• The 5th argument for initialization is batch_first(Optional-Default:False-Type:bool).
• The 6th argument for initialization is dropout(Optional-Default:0.0-Type:int or float). *It must be 0 <= x <= 1.
• The 7th argument for initialization is bidirectional(Optional-Default:False-Type:bool). *If it's True, bias_ih_lx_reverse, bias_hh_lx_reverse, weight_ih_lx_reverse and weight_hh_lx_reverse are added.
• The 8th argument for initialization is proj_size(Optional-Default:0-Type:int). *It must be 0 < hidden_size.
• The 9th argument for initialization is device(Optional-Default:None-Type:str, int or device()): *Memos:
  • If it's None, get_default_device() is used. *My post explains get_default_device() and set_default_device().
  • device= can be omitted.
  • My post explains device argument.
• The 10th argument for initialization is dtype(Optional-Default:None-Type:int): *Memos:
  • If it's None, get_default_dtype() is used. *My post explains get_default_dtype() and set_default_dtype().
  • dtype= can be omitted.
  • My post explains dtype argument.
• The 1st argument is input(Required-Type:tensor of float or complex): *Memos:
  • Its device and dtype must be same as LSTM()'s.
  • complex must be set to dtype of LSTM() to use a complex tensor.
  • The tensor's requires_grad which is False by default is set to True by LSTM().
• lstm1.device and lstm1.dtype don't work.

import torch
from torch import nn

tensor1 = torch.tensor([[8., -3., 0., 1., 5., -2.]])

tensor1.requires_grad
# False

torch.manual_seed(42)

lstm1 = nn.LSTM(input_size=6, hidden_size=3)

tensor2 = lstm1(input=tensor1)
tensor2
# (tensor([[-0.2443, 0.0840, 0.4837]], grad_fn=<SqueezeBackward1>),
# (tensor([[-0.2443, 0.0840, 0.4837]], grad_fn=<SqueezeBackward1>),
#  tensor([[-0.2616, 0.0902, 0.5288]], grad_fn=<SqueezeBackward1>)))

tensor2[0].requires_grad
tensor2[1][0].requires_grad
tensor2[1][1].requires_grad
# True

lstm1
# LSTM(6, 3)

lstm1.input_size
# 6

lstm1.hidden_size
# 3

lstm1.num_layers
# 1

lstm1.bias
# True

lstm1.batch_first
# False

lstm1.dropout
# 0.0

lstm1.bidirectional
# False

lstm1.proj_size
# 0

lstm1.bias_ih_l0
# Parameter containing:
# tensor([-0.5053, -0.3676, 0.5771, 0.1090, 0.1779, -0.5385,
#         -0.3792, -0.1922, 0.0903, -0.5080, -0.2488, -0.3456],
#        requires_grad=True)

lstm1.bias_hh_l0
# Parameter containing:
# tensor([0.0016, -0.2148, -0.0400, -0.3912, -0.3963, -0.3368,
#         -0.1976, -0.4557, 0.4841, -0.1146,  0.4968,  0.1799],
#        requires_grad=True)

lstm1.weight_ih_l0
# Parameter containing:
# tensor([[0.4414, 0.4792, -0.1353, 0.5304, -0.1265, 0.1165],
#         [-0.2811, 0.3391, 0.5090, -0.4236, 0.5018, 0.1081],
#         [0.4266, 0.0782, 0.2784, -0.0815, 0.4451, 0.0853],
#         [-0.2695, 0.1472, -0.2660, -0.0677, -0.2345, 0.3830],
#         [-0.4557, -0.2662, -0.1630, -0.3471, 0.0545, -0.5702],
#         [0.5214, -0.4904, 0.4457, 0.0961, -0.1875, 0.3568],
#         [0.0900, 0.4665, 0.0631, -0.1821, 0.1551, -0.1566],
#         [0.2430, 0.5155, 0.3337, -0.2524, 0.3333, 0.1033],
#         [0.2932, -0.3519, -0.5715, -0.2231, -0.4428, 0.4737],
#         [0.1663, 0.2391, 0.1826, -0.0100, 0.4518, -0.4102],
#         [0.0364, -0.3941, 0.1780, -0.1988, 0.1769, -0.1203],
#         [0.4788, -0.3422, -0.3443, -0.3444, 0.5193, 0.1924]],
#        requires_grad=True)

lstm1.weight_hh_l0
# Parameter containing:
# tensor([[0.5556, -0.4765, -0.5727],
#         [-0.4517, -0.3884, 0.2339],
#         [0.2067, 0.4797, -0.2982],
#         [-0.3936, 0.3063, -0.2334],
#         [0.3504, -0.1370, 0.3303],
#         [-0.4486, -0.2914, 0.1760],
#         [0.1221, -0.1472, 0.3441],
#         [0.3925, -0.4187, -0.3082],
#         [0.5287, -0.1948, -0.2047],
#         [-0.5586, -0.3306, 0.1442],
#         [-0.0762, -0.4191, 0.0135],
#         [-0.3944, -0.4898, -0.3179]], requires_grad=True)

torch.manual_seed(42)

lstm2 = nn.LSTM(input_size=3, hidden_size=3)

lstm2(input=tensor2[0])
lstm2(input=tensor2[1][0])
# (tensor([[0.0832, 0.0755, 0.0117]], grad_fn=<SqueezeBackward1>),
# (tensor([[0.0832, 0.0755, 0.0117]], grad_fn=<SqueezeBackward1>),
#  tensor([[0.1856, 0.1574, 0.0294]], grad_fn=<SqueezeBackward1>)))

lstm2(input=tensor2[1][1])
# (tensor([[0.0803, 0.0776, 0.0118]], grad_fn=<SqueezeBackward1>),
# (tensor([[0.0803, 0.0776, 0.0118]], grad_fn=<SqueezeBackward1>),
#  tensor([[0.1810, 0.1612, 0.0293]], grad_fn=<SqueezeBackward1>)))

lstm2(input=tensor2[1])
# (tensor([[-0.4656, 0.5770, 0.0342]], grad_fn=<SqueezeBackward1>),
#  tensor([[-0.4656, 0.5770, 0.0342]], grad_fn=<SqueezeBackward1>))

torch.manual_seed(42)

lstm = nn.LSTM(input_size=6, hidden_size=3, num_layers=1, bias=True, 
               batch_first=False, dropout=0.0, bidirectional=False,
               proj_size=0, device=None, dtype=None)
lstm(input=tensor1)
# (tensor([[-0.2443, 0.0840, 0.4837]], grad_fn=<SqueezeBackward1>),
# (tensor([[-0.2443, 0.0840, 0.4837]], grad_fn=<SqueezeBackward1>),
#  tensor([[-0.2616, 0.0902, 0.5288]], grad_fn=<SqueezeBackward1>)))

my_tensor = torch.tensor([[8., -3., 0.],
                          [1., 5., -2.]])
torch.manual_seed(42)

lstm = nn.LSTM(input_size=3, hidden_size=3)
lstm(input=my_tensor)
# (tensor([[-0.0367, 0.4198, -0.0198],
#          [0.1306, -0.0044, -0.0685]], grad_fn=<SqueezeBackward1>),
# (tensor([[0.1306, -0.0044, -0.0685]], grad_fn=<SqueezeBackward1>),
#  tensor([[0.1737, -0.1024, -0.5664]], grad_fn=<SqueezeBackward1>)))

my_tensor = torch.tensor([[8.], [-3.], [0.],
                          [1.], [5.], [-2.]])
torch.manual_seed(42)

lstm = nn.LSTM(input_size=1, hidden_size=3)
lstm(input=my_tensor)
# (tensor([[-0.0166, 0.7330, 0.1206],
#          [0.1032, 0.1525, -0.1500],
#          [0.1405, 0.0611, -0.1123],
#          [0.1237, 0.0956, -0.0111],
#          [-0.0165, 0.6493, 0.1319],
#          [0.1539, 0.1300, -0.0973]], grad_fn=<SqueezeBackward1>),
# (tensor([[0.1539, 0.1300, -0.0973]], grad_fn=<SqueezeBackward1>),
#  tensor([[0.2453, 0.2261, -0.2197]], grad_fn=<SqueezeBackward1>)))

my_tensor = torch.tensor([[[8.], [-3.], [0.]],
                          [[1.], [5.], [-2.]]])
torch.manual_seed(42)

lstm = nn.LSTM(input_size=1, hidden_size=3)
lstm(input=my_tensor)
# (tensor([[[-0.0166, 0.7330, 0.1206],
#           [0.1708, -0.0301, -0.1611],
#           [0.1316, -0.0240, -0.0288]],
#          [[-0.1315, 0.3354, 0.1798],
#           [-0.0265, 0.6095, -0.0510],
#           [0.2242, -0.0561, -0.1505]]], grad_fn=<MkldnnRnnLayerBackward0>),
# (tensor([[[-0.1315, 0.3354, 0.1798],
#           [-0.0265, 0.6095, -0.0510],
#           [0.2242, -0.0561, -0.1505]]], grad_fn=<StackBackward0>),
#  tensor([[[-0.4131, 0.4074, 0.3478],
#           [-0.3588, 0.7394, -0.0908],
#           [0.3819, -0.1140, -0.4157]]], grad_fn=<StackBackward0>)))

my_tensor = torch.tensor([[[8.+0.j], [-3.+0.j], [0.+0.j]],
                          [[1.+0.j], [5.+0.j], [-2.+0.j]]])
torch.manual_seed(42)

lstm = nn.LSTM(input_size=1, hidden_size=3, dtype=torch.complex64)
lstm(input=my_tensor)
# (tensor([[[0.0470+0.0483j, -0.0209+0.0511j, -0.0295+0.0117j],
#           [0.0148+0.3332j, -0.1477+0.6714j, -0.3587+0.2890j],
#           [-0.1949+0.0649j, 0.0522-0.1214j, -0.3186-0.1003j]],
#          [[-0.0046-0.0199j, -0.0496-0.0433j, 0.1316-0.2021j],
#           [0.1221+0.0741j, 0.1806+0.7882j, -0.0890-0.0377j],
#           [-0.2860+0.3574j, -0.0367+0.2503j, -0.3736+0.1591j]]],
#         grad_fn=<StackBackward0>),
# (tensor([[[-0.0046-0.0199j, -0.0496-0.0433j, 0.1316-0.2021j],
#           [0.1221+0.0741j, 0.1806+0.7882j, -0.0890-0.0377j],
#           [-0.2860+0.3574j, -0.0367+0.2503j, -0.3736+0.1591j]]],
#         grad_fn=<StackBackward0>),
#  tensor([[[-0.0076-0.0525j, -0.0391-0.1021j, 0.3074-0.3711j],
#           [0.9092+0.1833j, -0.1939+1.1534j, -0.2418+0.1878j],
#           [-0.5759+0.6338j, -0.1179+0.3004j, -0.5170+0.0107j]]],
#         grad_fn=<StackBackward0>)))