GCC Code Coverage Report

Directory: src/athena/
File: athena_activation_relu.f90
Date: 2025-12-10 07:37:07
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1 module athena__activation_relu
2 !! Module containing implementation of the ReLU activation function
3 !!
4 !! This module implements the Rectified Linear Unit (ReLU) activation,
5 !! which zeroes negative values while preserving positive values.
6 !!
7 !! Mathematical operation:
8 !! \[ f(x) = \max(0, x) = \begin{cases} x & \text{if } x > 0 \\\\ 0 & \text{if } x \leq 0 \end{cases} \]
9 !!
10 !! Derivative:
11 !! \[ f'(x) = \begin{cases} 1 & \text{if } x > 0 \\\\ 0 & \text{if } x \leq 0 \end{cases} \]
12 !!
13 !! Properties: Non-saturating, sparse activation, mitigates vanishing gradients
14 !! Reference: Nair & Hinton (2010), ICML
15 use coreutils, only: real32, print_warning
16 use diffstruc, only: array_type, operator(*), max
17 use athena__misc_types, only: base_actv_type
18 use athena__misc_types, only: onnx_attribute_type
19 implicit none
20
21
22 private
23
24 public :: relu_actv_type, create_from_onnx_relu_activation
25
26
27 type, extends(base_actv_type) :: relu_actv_type
28 !! Type for ReLU activation function with overloaded procedures
29 contains
30 procedure, pass(this) :: apply => apply_relu
31 procedure, pass(this) :: reset => reset_relu
32 procedure, pass(this) :: apply_attributes => apply_attributes_relu
33 procedure, pass(this) :: export_attributes => export_attributes_relu
34 end type relu_actv_type
35
36 interface relu_actv_type
37 procedure initialise
38 end interface relu_actv_type
39
40
41
42 contains
43
44 !###############################################################################
45 − function initialise(scale, attributes) result(activation)
46 !! Initialise a ReLU activation function
47 implicit none
48
49 ! Arguments
50 real(real32), optional, intent(in) :: scale
51 !! Optional scale factor for activation output
52 type(relu_actv_type) :: activation
53 !! ReLU activation type
54 type(onnx_attribute_type), optional, intent(in) :: attributes(:)
55 !! Optional ONNX attributes
56
57
58 − call activation%reset()
59
60 − if(present(scale)) activation%scale = scale
61 − if(abs(activation%scale-1._real32) .gt. 1.e-6_real32)then
62 − activation%apply_scaling = .true.
63 end if
64 − if(present(attributes))then
65 − call activation%apply_attributes(attributes)
66 end if
67
68 − end function initialise
69 !-------------------------------------------------------------------------------
70 − pure subroutine reset_relu(this)
71 !! Reset ReLU activation function attributes and variables
72 implicit none
73
74 ! Arguments
75 class(relu_actv_type), intent(inout) :: this
76 !! ReLU activation type
77
78 − this%name = "relu"
79 − this%scale = 1._real32
80 − this%threshold = 0._real32
81 − this%apply_scaling = .false.
82
83 − end subroutine reset_relu
84 !-------------------------------------------------------------------------------
85 − function create_from_onnx_relu_activation(attributes) result(activation)
86 !! Create ReLU activation function from ONNX attributes
87 implicit none
88
89 ! Arguments
90 type(onnx_attribute_type), dimension(:), intent(in) :: attributes
91 !! Array of ONNX attributes
92
93 class(base_actv_type), allocatable :: activation
94 !! Instance of activation type
95
96 − allocate(activation, source = relu_actv_type(attributes = attributes))
97
98 − end function create_from_onnx_relu_activation
99 !###############################################################################
100
101
102 !###############################################################################
103 − subroutine apply_attributes_relu(this, attributes)
104 !! Load ONNX attributes into ReLU activation function
105 implicit none
106
107 ! Arguments
108 class(relu_actv_type), intent(inout) :: this
109 !! ReLU activation type
110 type(onnx_attribute_type), dimension(:), intent(in) :: attributes
111 !! Array of ONNX attributes
112
113 ! Local variables
114 integer :: i
115 !! Loop variable
116 type(onnx_attribute_type) :: attribute
117 !! Temporary attribute holder
118 character(20), allocatable, dimension(:) :: attribute_names
119
120 ! Load provided attributes
121 − do i=1, size(attributes,dim=1)
122 − select case(trim(attributes(i)%name))
123 case("scale")
124 − read(attributes(i)%val,*) this%scale
125 − if(abs(this%scale-1._real32) .gt. 1.e-6_real32)then
126 − this%apply_scaling = .true.
127 else
128 − this%apply_scaling = .false.
129 end if
130 case("threshold")
131 − read(attributes(i)%val,*) this%threshold
132 case("name")
133 − if(trim(attributes(i)%val) .ne. trim(this%name)) then
134 call print_warning( &
135 'ReLU activation: name attribute "' // &
136 − trim(attributes(i)%val) // &
137 '"" does not match expected "' // trim(this%name)//'"' &
138 − )
139
140 end if
141 case default
142 call print_warning( &
143 − 'ReLU activation: unknown attribute '//trim(attributes(i)%name) &
144 − )
145 end select
146 end do
147
148 − end subroutine apply_attributes_relu
149 !###############################################################################
150
151
152 !###############################################################################
153 − pure function export_attributes_relu(this) result(attributes)
154 !! Export ReLU activation function attributes as ONNX attributes
155 implicit none
156
157 ! Arguments
158 class(relu_actv_type), intent(in) :: this
159 !! ReLU activation type
160 type(onnx_attribute_type), allocatable, dimension(:) :: attributes
161 !! Array of ONNX attributes
162
163 ! Local variables
164 character(50) :: buffer
165 !! Temporary string buffer
166
167 − allocate(attributes(3))
168
169 − write(buffer, '(A)') this%name
170 − attributes(1) = onnx_attribute_type( &
171 − "name", "string", trim(adjustl(buffer)) )
172
173 − write(buffer, '(F10.6)') this%scale
174 − attributes(2) = onnx_attribute_type( &
175 − "scale", "float", trim(adjustl(buffer)) )
176
177 − write(buffer, '(F10.6)') this%threshold
178 − attributes(3) = onnx_attribute_type( &
179 − "threshold", "float", trim(adjustl(buffer)) )
180
181 − end function export_attributes_relu
182 !###############################################################################
183
184
185 !###############################################################################
186 − function apply_relu(this, val) result(output)
187 !! Apply ReLU activation to 1D array
188 !!
189 !! Computes: f = max(0,x)
190 implicit none
191
192 ! Arguments
193 class(relu_actv_type), intent(in) :: this
194 !! ReLU activation type
195 type(array_type), intent(in) :: val
196 !! Input values
197 type(array_type), pointer :: output
198 !! Activated output values
199
200 − if(this%apply_scaling)then
201 − output => max(val, this%threshold) * this%scale
202 else
203 − output => max(val, this%threshold)
204 end if
205 − end function apply_relu
206 !###############################################################################
207
208 − end module athena__activation_relu
209