Hardware Dependencies and Configurability

Global Definitions and Library Configurability

All configurable global definitions and constants are defined in ./include/mli_config.h. This header file is not included in ./include/mli_api.h header and should be included implicitly in user code in case its content might be useful. For example, use ARC_PLATFORM define for multi-platform applications.

Target Platform Definition (ARC_PLATFORM)

ARC_PLATFORM defines main platform type that the library is built for. By default this is determined in compile time according to the TCF file. To explicitly set the platform, set ARC_PLATFORM to one of the following macros in advance:

  • V2DSP – using ARCv2DSP ISA extensions only (EM5D or EM7D).
  • V2DSP_WIDE – using wide ARCv2DSP ISA extensions (HS45D or HS47D)
  • V2DSP_XY – using ARCv2DSP ISA extensions and AGU (EM9D or EM11D).

Function Parameters Examination and Debug (MLI_DEBUG_MODE)

The MLI Library supports five debug modes. You can choose the debug mode by setting MLI_DEBUG_MODE define as follows:

  • DBG_MODE_RELEASE (MLI_DEBUG_MODE = 0) - No debug. Functions do not examine parameters. Data is processed with assumption that function input is valid. This might lead to undefined behavior if the assumption is not true. Functions always return MLI_STATUS_OK. No messages are printed, and no assertions are used.
  • DBG_MODE_RET_CODES (MLI_DEBUG_MODE = 1) – Functions examine parameters and return valid error status if any violation of data is found. Else, functions process data and return status MLI_STATUS_OK. No messages are printed and no assertions are used.
  • DBG_MODE_ASSERT (MLI_DEBUG_MODE = 2) - Functions examine parameters. Any violation of data found lead to break on assert()
  • DBG_MODE_DEBUG (MLI_DEBUG_MODE = 3) - The same as DBG_MODE_ASSERT, but before breaking on assert() function prints descriptive message using standard printf()
  • DBG_MODE_FULL (MLI_DEBUG_MODE = 4) - The same as DBG_MODE_DEBUG, but additionally extra assertions inside loops are used for this mode.

By default, MLI_DEBUG_MODE is set to DBG_MODE_RELEASE. The following table specifies modes behavior.

MLI_DEBUG_MODE modes behavior
Assertions NO NO YES YES YES
Extra Assertions NO NO NO NO YES

Concatenation Primitive: Maximum Tensors to Concatenate (MLI_CONCAT_MAX_TENSORS)

This primitive configures maximum number of tensors for concatenation by appropriate primitive (see Concatenation ). Default: 8.

Memory Allocation

The MLI library does not allocate any memory dynamically. Your application is responsible for providing correct parameters for function and allocate memory for it if necessary. The MLI library might use internal statically allocated data (tables of constants).

Hardware Components Dependencies

DSP Control

The MLI Library intensively uses ARCv2DSP extension of ARC EM and ARC HS processors. Ensure that this extension is present and correctly configured in hardware.

Ensure that you build the library with the appropriate command line parameter:


Where “up” defines the rounding mode of DSP hardware (rounding up) and it is the only parameter which might be changed (to “convergent” - round to the nearest even). All parameters are described in MetaWare Fixed-Point Reference for ARC EM and ARC HS.


The MLI Library sets the required DSP mode inside each function where it is needed, but does not restore it to previous state. If another ARC DSP code beside MLI library is used in an application, ensure that you set the required DSP mode before its execution. For more information see “Configuring the ARC DSP Extensions” section of MetaWare DSP Programming Guide for ARC EM and ARC HS or “Using the FXAPI” section of MetaWare Fixed-Point Reference for ARC EM and ARC HS.

AGU Support

The MLI Library is optimized for systems with and without AGU (address generation unit). If AGU is present in the system, then library code optimized for AGU is compiled automatically, otherwise the AGU optimization is not used (see Target Platform Definition (ARC_PLATFORM)). Inside primitives, pointers to some data defined with use of MLI_PTR(p) macro expand into __xy p * in AGU systems, and to p * in system without AGU. An application is responsible for allocation of relevant buffers in the AGU memory region (for more information see “XY Memory Optimization” chapter of MetaWare DSP Programming Guide for ARC EM and ARC HS).

AGU Requirements for Tensors provides information about tensors must be allocated into AGU-accessible memory for each primitive. Tensors not mentioned in AGU Requirements for Tensors do not have to be allocated in the same way.

AGU Requirements for Tensors
Primitive Tensors That Must Be Allocated Into AGU-Accessible Memory
Convolution 2D in, weights, out, biases
Depthwise convolution in, weights, out, biases
Max Pooling in, out
Average Pooling in, out
Fully connected in, out
Long Short Term Memory in, weights, biases, out, prev_out, ir_tsr
Basic RNN cell in, weights, biases, out, prev_out, ir_tsr
ReLU in, out
Leaky ReLU in, out
Sigmoid in, out
TanH in, out
Softmax in, out
Eltwise add/subtract/max/multiplication in1, in2, out
Padding 2D