Importing Stream-Based Kernels - 2022.1 English

As an example, to import a simple kernel with a stream-based interface, the following simple.h header file declares the simple_comp function with one input stream and one output stream.

#ifndef __COMPLEX_KERNEL_H__
#define __COMPLEX_KERNEL_H__
#include <adf.h>
  void simple_comp(input_stream_cint16 * in, output_stream_cint16 * out);
#endif //__COMPLEX_KERNEL_H__

The function is defined in simple.cc.

#include "simple.h"
void simple_comp(input_stream_cint16 * in, output_stream_cint16 * out) {
  cint16 c1, c2;
 
  for (unsigned i=0; i<NUM_SAMPLES; i++) {
  c1 = readincr(in);
  c2.real = c1.real+c1.imag;
  c2.imag = c1.real-c1.imag;
  writeincr(out, c2);
}
}

Although, the function arguments for window-based and stream-based kernels are different, the procedure for importing the stream-based kernel is the same.

After a successful import, the Function tab GUI displays automatically. You can quickly review the function definition and ports as shown in the following figure.

The following table provides details on the parameters and a description for each parameter.

In the General tab, the Import button changes to Update, enabling further updates of block parameters.

Model Composer also supports cascade stream connections between two AI Engine processors.

An AI Engine kernel can use incoming stream connections as follows:

• Input_stream_acc48
• Input_stream_cacc48

Similarly, a kernel can use the outgoing cascade stream connections as follows:

In Model Composer, a cascade stream port is represented as a 48-bit fixed point signal (x_sfix48) that can be either complex or real.

Consider the following example, where a cascade output stream of one kernel is connected to the cascade input stream of another kernel.

#ifndef __CASCADE_KERNELS_H__
#define __CASCADE_KERNELS_H__
void f_osacc48(input_window_int32 *i_hi, 
               input_window_int16 *i_lo, 
               output_stream_acc48 *o1);
#endif

After importing this kernel function, the AIE Kernel block is as shown in the following figure.

Consider another kernel function f_isacc48, which has one cascade stream input: i1, and two output windows: o_hi and o_lo.

#ifndef __CASCADE_KERNELS_H__
#define __CASCADE_KERNELS_H__
void f_isacc48(input_stream_acc48 *i1,
               output_window_int32 *o_hi,
               output_window_int16 *o_lo);
#endif

After importing the second kernel function, the AIE Kernel block is as shown in the following figure.

Now the two kernels can be connected to form a cascade connection using the cascade stream output of block f_osacc48 and the cascade stream input of block f_isaccc48. This is shown in the following figure.