Programming Model Features - 2022.1 English

Versal ACAP AI Engine Programming Environment User Guide (UG1076)

Document ID
Release Date
2022.1 English

The AI Engine programming model has the following features.

  • All I/O objects (input_plio/output_plio and input_gmio/output_gmio) are public members of graph class. Looping through I/O objects is supported. This makes I/O objects construction easier and fewer errors. For example:
    class mygraph : public graph
        // Declare N kernels.
        kernel k[N];
        // Declare N input_gmio(s) and output_gmio(s)
        input_gmio gmioIn[N];
        output_gmio gmioOut[N];
            // Create multiple input_gmio(s)/output_gmio(s) and connections
            for (int i=0; i<N; i++)
                gmioIn[i]  = input_gmio::create("gmioIn" + std::io_string(i), 64, 1);
                gmioOut[i] = output_gmio::create("gmioOut" + std::io_string(i), 64, 1);
                connect<window<128>>(gmio[i].out[0], k[i].in[0]);
                connect<window<128>>(k[i].out[0], gmioOut[i].in[0]);
    Note: While not required, you can provide a logical name when creating the input_plio, output_plio, input_gmio and output_gmio objects. If not provided, the AI Engine compiler will automatically set a unique logical name.
  • The programming model provides ease of use for connections within the design. With the input_plio, output_plio, input_gmio and output_gmio objects in the local scope, connect<> calls are not required to provide a unique connection name.
  • The programming model supports the direction property of input_plio, output_plio, input_gmio and output_gmio objects. The direction property is determined within object construction.

An example of the programming model that addresses these previously listed features is as follows.

/* A graph with both PLIO and GMIO*/
class mygraph : graph

    /* Classes support input_gmio/output_gmio and input_plio/output_plio */
    input_gmio gm_in; 
    output_gmio gm_out;

    input_plio pl_in;
    output_plio pl_out;

    kernel k1, k2;
        k1 = kernel::create(...);
        k2 = kernel::create(...);

        /* create() API for PLIO and GMIO objects support same arguments specified as in global scope */
        gm_in = input_gmio::create("GMIO_In0",/*const std::string& logical_name*/
                                    64,       /*size_t burst_length*/
                                    1         /*size_t bandwidth*/);

        gm_out = output_gmio::create("GMIO_Out0", 64, 1);

        pl_in = input_plio::create("PLIO_In0",       /* std::string logical_name */
                                    plio_32_bits,    /* enum plio_type plio_width */
                                    "data/input.txt",/* std::string data_file */
                                    250.0            /* double frequency */ );

        pl_out = output_plio::create("PLIO_Out0", plio_32_bits, "data/output.txt", 250.0);

        /* Each input_gmio/output_gmio and input_plio/output_plio supports 1 port per direction */


        location<GMIO>(gm_in) = shim(col);
        location<GMIO>(gm_out) = shim(col, ch_num); /* not supported */

        location<PLIO>(pl_in) = shim(col);
        location<PLIO>(pl_out) = shim(col, ch_num);


The previous code snippet demonstrates:

  • input_plio, output_plio, input_gmio, and output_gmio are public objects within the graph.
  • input_plio, and output_plio classes are inherited from the PLIO class.
  • input_gmio, and output_gmio classes are inherited from the GMIO class.
  • input_plio, output_plio, input_gmio, and output_gmio object constructions contain the direction property.
  • connect call does not require unique name.
  • Location constraints can be applied to the input_plio, output_plio, input_gmio, and output_gmio objects directly with the exception of GMIO channel constraints which are not supported in this release.
    Note: GMIO shim tile location constraint with DMA channel is not supported.
    Note: Host application calling profiling APIs need reference object’s public members, mygraph.gm_in, mygraph.gm_out, mygraph.pl_in, mygraph.pl_out. See Performance Analysis of AI Engine Graph Application during Simulation for additional details about profiling APIs.

    An example of a profile call from programming model is as follows.

    event::handle handle0 = event::start_profiling(mygraph.gm_in, event::io_stream_start_to_bytes_transferred_cycles, sizeIn*sizeof(cint16));
Important: The input_plio, output_plio, input_gmio, and output_gmio objects must have a unique name. If a name is not unique, the following error message is issued:
ERROR: [aiecompiler 77-4551] The logical name DataIn1 of node i6 conflicts with the logical/qualified name of node i0.