Finally I came back to the hls version.
I had the baseline design work with a minor change on the while condition in the write process.
However, the performance is extremely bad. On alpha-data ADM-PCIE-7v3, the measured bandwidth is around
40MB/s ((read + write)/execution time). However, if there is no condition processing with a similar code, say I read in a stream, add a constant and write it back to out stream. The measured bandwidth is 1.4GB/s. So basically the write process is essentially writing the data one by one. It does no burst at all. Otherwise, the bandwidth should be at least 700MB/s.
To fix this problem, I plan to do batch writing. The basic idea is to buffer the output data and do a burst write when I get a specified number of data or it comes to the end of the writing process. However, I tired a number of ways to implement the logic but never succeed.
//==========================================
// Here is the code that works with bad performance
//==========================================
static void compute(
hls::stream<int> &in_stream,
hls::stream<char> &done_stream,
hls::stream<int> &im_stream,
int size)
{
filtering: for (int i = 0; i < size; i++){
#pragma HLS pipeline
#pragma HLS LOOP_TRIPCOUNT min=16*1024 max=16*1024*1024
int data = in_stream.read();
if(data > 10){
im_stream << data;
}
if(i == size - 1){
done_stream << 1;
}
}
}
static void write(
hls::stream<int> &im_stream,
hls::stream<char> &done_stream,
int *out
)
{
int idx = 0;
while(!(im_stream.empty() && done_stream.read() == 1)){
#pragma HLS pipeline
if(!(im_stream.empty())){
int data = im_stream.read();
out[idx] = data + 10;
idx++;
}
}
}
//===================================
// Here is the code that I tried to batch writing
//====================================
static void write(
hls::stream<int> &im_stream,
hls::stream<char> &done_stream,
hls::stream<char> &duplicated_done_stream,
int *out
)
{
int idx = 0;
int counter = 0;
int buffer[256];
while(!(done_stream.read() == 1 && im_stream.empty())){
if(!(im_stream.empty())){
int im = im_stream.read();
buffer[counter] = im + 10;
counter++;
if(counter == 256){
#pragma HLS pipeline
for(int i = 0; i < 256; i++){
out[idx] = buffer[i];
idx++;
}
counter = 0;
}
}
}
char done;
dulicated_done_stream.read_nb(done);
if(done){
// Process the last batch
#pragma HLS pipeline
for(int i = counter; i < 256; i++){
buffer[i] = -1;
}
#pragma HLS pipeline
for(int i = 0; i < 256; i++){
out[idx] = buffer[i];
idx++;
}
}
}
However, I get the following error at sw_emu mode, which I don't quite understand.
Not sure how to resolve it. Hope to get some suggestions on this as well.
ERROR: Kernel execution failed. Kernel exited with the code 11
ERROR: cu monitor died unexpectedly: cu monitor stopping while there are active cu events
terminate called without an active exception
ERROR: Kernel execution failed. Kernel exited with the code 6
../../..//utility/check.mk:59: recipe for target 'check_sw_emu_xilinx_adm-pcie-7v3_1ddr_3_0_check' failed
make: *** [check_sw_emu_xilinx_adm-pcie-7v3_1ddr_3_0_check] Error 1
