场景 1:包含串流接口的自动重启内核 - 2022.1 简体中文

Vitis 统一软件平台文档 应用加速开发 (UG1393)

Document ID
UG1393
Release Date
2022-05-25
Version
2022.1 简体中文
自动重启内核会一直运行直至复位。如果内核包含串流接口,那么主机代码应该能够使用软件复位功能停止内核。要定义此行为,必须使用全局配置选项在 Vitis HLS 中配置内核,如下所示:
config_interface -s_axilite_auto_restart_counter 1
config_interface -s_axilite_sw_reset
提示: 要从 v++ -c 命令行指定 Vitis HLS 命令,请使用 --hls.pre_tcl 选项,如 --hls 选项 中所述。

自动重启内核的内核代码类似于以下示例:

#include "ap_axi_sdata.h"
#include "hls_stream.h"
 
typedef ap_axis<32, 0, 0, 0> pkt;
 
extern "C" {
10 void krnl_stream_vdatamover(hls::stream<pkt> &in,
11    hls::stream<pkt> &out  // Internal Stream
12    ) {
13 #pragma HLS interface ap_ctrl_chain port=return
14 bool eos = false;
15 vdatamover:
16   do {
17     // Reading a and b streaming into packets
18     pkt t1 = in.read();
19 
20     // Packet for output
21     pkt t_out;
22 
23     // Reading data from input packet
24     ap_uint<DWIDTH> in1 = t1.data;
25 
26     // Vadd operation
27     ap_uint<DWIDTH> tmpOut = in1;
28 
29     // Setting data and configuration to output packet
30     t_out.data = tmpOut;
31     t_out.last = t1.last;
32     t_out.keep = -1; // Enabling all bytes
33 
34     // Writing packet to output stream
35     out.write(t_out);
36 
37     if (t1.last) {
38        eos = true;
39     }
40   } while (eos == false);

使用 XRT 本机 API,主机应用要求使用 xrt::autostart API 将内核设置为自动重启模式,如下所示。在主机应用中创建 XRT 运行对象,并在 autostart 模式中进行设置。这将指定 xrt::autostart{0},表示重新启动内核的迭代次数无限制。

由于内核包含串流接口,因此内核将不会自行停止,原因是串流接口没有启动和停止机制。在此情况下,主机应用可使用 abort() 方法显式停止内核。

// add(in1, in2, nullptr, data_size)
  xrt::kernel add(device, uuid, "krnl_stream_vadd");
  xrt::bo in1(device, data_size_bytes, add.group_id(0));
  auto in1_data = in1.map<int*>();
  xrt::bo in2(device, data_size_bytes, add.group_id(1));
  auto in2_data = in2.map<int*>();
 
  // mult(in3, nullptr, out, data_size)
  xrt::kernel mult(device, uuid, "krnl_stream_vmult");
  xrt::bo in3(device, data_size_bytes, mult.group_id(0));
  auto in3_data = in3.map<int*>();
  xrt::bo out(device, data_size_bytes, mult.group_id(2));
  auto out_data = out.map<int*>();
 
 
  xrt::kernel incr(device, uuid, "krnl_stream_vdatamover");
  // create run objects for re-use in loop
  xrt::run add_run(add);
  xrt::run mult_run(mult);
   
  std::cout <<"performing auto-restart mode with infinite auto restart"<<std::endl;
  auto incr_run = incr(xrt::autostart{0}, nullptr, nullptr, nullptr, nullptr);
 
  // computed expected result
  std::vector<int> sw_out_data(data_size);
 
  std::cout << " for loop started" <<std::endl;
  bool error = false;   // indicates error in any of the iterations
  for (unsigned int cnt = 0; cnt < iter; ++cnt) {
 
    
    // Create the test data and software result
    for(size_t i = 0; i < data_size; ++i) {
      in1_data[i] = static_cast<int>(i);
      in2_data[i] = 2 * static_cast<int>(i);
      in3_data[i] = static_cast<int>(i);
      out_data[i] = 0;
      sw_out_data[i] = (in1_data[i] + in2_data[i] + adder1 + adder2) * in3_data[i];
    }
 
    // sync test data to kernel
    in1.sync(XCL_BO_SYNC_BO_TO_DEVICE);
    in2.sync(XCL_BO_SYNC_BO_TO_DEVICE);
    in3.sync(XCL_BO_SYNC_BO_TO_DEVICE);
 
    // start the pipeline
    add_run(in1, in2, nullptr, data_size);
    mult_run(in3, nullptr, out, data_size);
 
    // wait for the pipeline to finish
    add_run.wait();
    mult_run.wait();
 
    // sync result from device to host
    out.sync(XCL_BO_SYNC_BO_FROM_DEVICE);
 
    // compare with expected scalar adders
    for (size_t i = 0 ; i < data_size; i++) {
      if (out_data[i] != sw_out_data[i]) {
        std::cout << "error in iteration = " << cnt
                  << " expected output = " << sw_out_data[i]
                  << " observed output = " << out_data[i]
                  << " adder1 = " << adder1 - 1
                  << " adder2 = " << adder2 + 1 << '\n';
        throw std::runtime_error("result mismatch");
      }
    }
  }
// auto restart kernel would require the host to stop it explicitly
        incr_run.abort();
}