//
// This confidential and proprietary software may be used only as
// authorised by a licensing agreement from ARM Limited
// (C) COPYRIGHT 2020-2021 ARM Limited
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=== Activation Functions

==== CLAMP
Clamp to an arbitrary minimum and maximum value. Note that the maximum and minimum values are specified as signed quantized values, no scaling happens before or after this operation.

*Arguments:*

|===
|Argument|Type|Name|Shape|Description

|Input|in_t*|Input|shape|Input tensor
|Attribute|in_t|min_val|-|minimum clip value
|Attribute|in_t|max_val|-|maximum clip value
|Output|in_t*|Output|shape|Output tensor of same type and shape as input
|===

*Operation Function:*
[source,c++]
----
for_each(index in shape) {
    acc_t value = tensor_read<in_t>(input, shape, index);
    acc = (in_t)apply_clip<acc_t>(value, min_val, max_val);
    tensor_write<in_t>(output, shape, index, acc);
}
----

*Supported Data Types:*

|===
|Profile|Mode|in_t|acc_t

|Any|signed 8|int8_t|int16_t
|Any|signed 16|int16_t|int16_t
|MI, MT|floating-point|float_t|float_t
|===

==== SIGMOID

Sigmoid function: output = 1 / (1 + exp(-input))

For quantized integer data types, the TABLE operator should be used instead with
the following definition.

The sigmoid table has 513 entries each of 16-bit precision and covering the input range -16.0 to +16.0 in steps of 1/16.

[source,c++]
----
int sigmoid_reference(int x) {|// input x range is -256 to + 256 inclusive
    F64 v = (double)x / (double)16;
    v = 1.0/(1.0 + exp(-v));
    return round_to_nearest_int(32768.0 * v);
}

generate_lookup_table(&sigmoid_table, &sigmoid_reference);
----

*Arguments:*

|===
|Argument|Type|Name|Shape|Description

|Input|in_t*|Input|shape|Input tensor
|Output|in_t*|Output|shape|Output tensor of same type and shape as input
|===

*Supported Data Types:*

|===
|Profile|Mode|in_t

|MI, MT|floating-point|float_t
|===

==== TANH

Parameterized hyperbolic tangent.

For quantized integer data types, the TABLE operator should be used instead with
the following definition.

The tanh_table has 513 entries each of 16-bit precision and covering the input range -8.0 to +8.0 in steps of 1/32. The table is specified by:

[source,c++]
----
int tanh_reference(int x) {  // input x range is -256 to +256 inclusive
    F64 v = (double)x/(double)32;
    v = exp(-2.0*v);
    v = (1.0-v)/(1.0+v);
    return round_to_nearest_int(32768.0 * v);
}

generate_lookup_table(&tanh_table, &tanh_reference);
----

*Arguments:*

|===
|Argument|Type|Name|Shape|Description

|Input|in_t*|Input|shape|Input tensor
|Output|in_t*|Output|shape|Output tensor of same type and shape as input
|===

*Supported Data Types:*

|===
|Profile|Mode|in_t

|MI, MT|floating-point|float_t
|===