The following graph control API shows how to use graph APIs to
initialize, run, wait, and terminate graphs for a specific number of iterations. A
graph object mygraph is declared using a
pre-defined graph class called simpleGraph. Then,
in the main application, this graph object is
initialized and run. The init() method loads the
graph to the AI Engine array at prespecified
AI Engine tiles. This includes loading the
ELF binaries for each AI Engine, configuring the
stream switches for routing, and configuring the DMAs for I/O. It leaves the
processors in a disabled state. The run() method
starts the graph execution by enabling the processors. The run API is where a specific number of iterations of the graph can be
run by supplying a positive integer argument at run time. This form is useful for
debugging your graph execution.
#include "project.h"
simpleGraph mygraph;
int main(void) {
mygraph.init();
mygraph.run(3); // run 3 iterations
mygraph.wait(); // wait for 3 iterations to finish
mygraph.run(10); // run 10 iterations
mygraph.end(); // wait for 10 iterations to finish
return 0;
}The API wait() is used to wait for
the first run to finish before starting the second run. wait has the same blocking effect as end except that it allows re-running the graph again without having to
re-initialize it. Calling run back-to-back without
an intervening wait to finish that run can have an
unpredictable effect because the run API modifies
the loop bounds of the active processors of the graph.
Graph Iteration
A graph can have multiple kernels, input and output ports. The graph connectivity, which is equivalent to the nets in a data flow graph is either between the kernels, between kernel and input ports, or between kernel and output ports, and can be configured as a connection. A graph runs for an iteration when it consumes data samples equal to the window or stream of data expected by the kernels in the graph, and produces data samples equal to the window or stream of data expected at the output of all the kernels in the graph.