Cpp Development

If you are interested in creating additional functionality for Bifrost, this document should help you get up and running with the Bifrost C++ API.

Contents

1. Create a Ring Buffer and Load Data

Create a Ring Buffer and Load Data

#include <cuda_runtime_api.h>
#include <bifrost/common.h>
#include <bifrost/ring.h>

...

//////////////////////////////////
//Create and write to a ring
/////////////////////////////////

BFring my_ring; //declare our ring variable
bfRingCreate(&my_ring, BF_SPACE_SYSTEM); //initiate this ring on local memory (=BF_SPACE_SYSTEM)
bfRingBeginWriting(my_ring); //begin writing to this ring
//generate some dummy variables
BFoffset skip_time_tag = -1;
BFoffset skip_offset = 0;
BFsize my_header_size = 0;
char *my_header = "";
//Set our ring variables
BFsize nringlets = 1; //dimensionality of our ring.
BFsize nbytes = 32*8; //number of bytes we are putting in
BFsize buffer_bytes = 4*nbytes;
//resize ring to fit the data
bfRingResize(
    my_ring, nbytes, buffer_bytes, nringlets);
//open a sequence on the ring.
BFwsequence my_sequence;
const char* name = "mysequence"; //we can find our sequence by this name later on
bfRingSequenceBegin(
    &my_sequence, my_ring, name, skip_time_tag,
    my_header_size, (const void*)my_header, nringlets, 
    skip_offset);
//reserve a "span" on this sequence to put our data
BFwspan my_span;
bfRingSpanReserve(
    &my_span, my_ring, nbytes);
void *data_access; //create a pointer to pass our data to
//create the data and copy it to the ring
float data[8] = {10, -10, 0, 0, 1, -3, 1, 0};
bfRingSpanGetData((BFspan)my_span, &data_access); //point our pointer to the span's allocated memory 
memcpy(data_access, &data, nbytes);
//stop writing
bfRingSpanCommit(my_span, nbytes); //commit this span to memory
bfRingSequenceEnd(my_sequence, skip_offset); //end off the sequence
bfRingEndWriting(my_ring);

//////////////////////////////////
//Read from the ring
/////////////////////////////////

nbytes = 32*8; //the size of the data we want to read
//open the last accessed sequence 
BFrsequence my_read_sequence;
bfRingSequenceOpenLatest(
    &my_read_sequence, my_ring, true);
//open a span on this sequence
BFrspan my_read_span;
bfRingSpanAcquire(
    &my_read_span, my_read_sequence, skip_offset, nbytes);
//Access the data from the span with a pointer
bfRingSpanGetData((BFspan)my_read_span, &data_access);
float *my_data = static_cast<float*>(data_access); //Copy the data into a readable format
//print out the ring data
for (int i = 0; i < 8; i++)
{
    printf("%f\n",my_data[i]);
}
//close up our ring access
bfRingSpanRelease(my_read_span);
bfRingSequenceClose(my_read_sequence);
bfRingDestroy(my_ring); //delete the ring from memory