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recv

virtual Request* recv(int vn) = 0;

Receive a Request from the network on the specified virtual network (vn).

Requirements​

Network interface  
Return a Request that was received on virtual network vn. If no Request exists, return nullptr.

Endpoint  
Call this function to get a request from the network.

Parameters​

  • vn (int) Virtual network to receive on
  • returns (Request*) Request that has been delivered or nullptr if none is available. Caller is responsible for deleting any event returned.

Examples​

Example 1: Implementing recv() in a SimpleNetwork interface​

Excerpt from sst-elements/src/sst/elements/merlin/interfaces/linkControl.cc

// Returns nullptr if no event in input_buf[vn]. Otherwise, returns
// the next event.
SST::Interfaces::SimpleNetwork::Request* LinkControl::recv(int vn) {
    if ( input_queues[vn].size() == 0 ) return nullptr; /* No events */

    RtrEvent* event = input_queues[vn].front();
    input_queues[vn].pop();

    /* Some bookkeeping to manage network credits for this event */

    SST::Interfaces::SimpleNetwork::Request* ret = event->takeRequest();
    if ( use_nid_map ) ret->dest = logical_nid; /* Merlin is maintaining aliases for network IDs */
    delete event;

    return ret; /* Return the Request */
}

Example 2: Polling SimpleNetwork from an endpoint​

In this example, the endpoint calls recv() in a clock handler function to check if anything has been received.

bool Endpoint::clockTick(SimCycle_t cycle)
{
    SST::Interfaces::SimpleNetwork::Request* req = net_iface->recv(0);
    if (req)
    {
        /* Got something - code to handle it here */
        delete req; /* Delete the request when we're done with it */
    }
    return false;
}

Example 3: Using a callback from an endpoint to receive a notification when a request is received​

In this example, the endpoint registers a callback function, requestAvailable() with a SimpleNetwork interface. Inside the callback, the endpoint uses recv() to acquire a Request.

Endpoint::Endpoint( ComponentId_t id, Params& params ) : Component(id)
{
    ...
    net_iface->setNotifyOnRecv(new SimpleNetwork::Handler<Endpoint>(this, &Endpoint::requestAvailable));
    ...
}

bool Endpoint::requestAvailable(int vn) {
    SST::Interfaces::SimpleNetwork::Request* req = net_iface->recv(vn);
    if (req) {
        /* Got something, code to handle it here */
        delete req;
    } else {
        /* That's strange, we were notified there was a request and it disappeared! */
    }
}
#include <sst/core/interfaces/simpleNetwork.h>