Local Memory Two Parallel Read/Write¶
This is simple example of vector addition to demonstrate how to utilize both ports of Local Memory.
KEY CONCEPTS: Kernel Optimization, 2port BRAM Utilization, two read/write Local Memory
KEYWORDS: #pragma HLS UNROLL FACTOR=2
This is a simple example to demonstrate how to utilize both ports of local memory in kernels.
Kernel’s local memory is usually BRAM
which has two ports for
read/write. In loops where one iteration doesn’t depend on previous
iterations, two ports can be used to improve the performance of the
kernel.
Two ports can be utilized concurrently by using pragma HLS UNROLL
.
The UNROLL pragma transform loops by creating multiples copies of the
loop body in the register transfer level (RTL) design, which allows some
or all loop iterations to occur in parallel.
#pragma HLS UNROLL FACTOR=2
Here loop is unrolled by a factor of 2 thus two iterations of the loop are executed concurrently. In this case, two ports of BRAM will be utilized rather than 1 reducing the total loop latency by half approximately.
vadd:
for (int j = 0; j < chunk_size; j++) {
#pragma HLS PIPELINE II=1
#pragma HLS UNROLL FACTOR=2
#pragma HLS LOOP_TRIPCOUNT min=c_chunk_sz max=c_chunk_sz
//perform vector addition
vout_buffer[j] = v1_buffer[j] + v2_buffer[j];
}
DESIGN FILES¶
Application code is located in the src directory. Accelerator binary files will be compiled to the xclbin directory. The xclbin directory is required by the Makefile and its contents will be filled during compilation. A listing of all the files in this example is shown below
src/host.cpp
src/vadd.cpp
COMMAND LINE ARGUMENTS¶
Once the environment has been configured, the application can be executed by
./host <vadd XCLBIN>