Skip to main content

spaceToSend

virtual bool spaceToSend(int vn, int num_bits) = 0;

Checks if there is sufficient space to send the specified number of bits on the specified virtual network.

Requirements​

Network interface  
Return whether the network interface can accept a Request of size num_bits on virtual network vn. Returning true implies that an immediately subsequent call to send() for a Request with this same number of bits and virtual network should succeed and return true as well.

Endpoint  
May optionally use this function to query available buffer space.

Parameters​

  • vn (int) Virtual network to check
  • num_bits (int) Number of bits to check for. If this number of bits can be accepted by the interface, the interface has space to send.
  • returns true if space exists, false otherwise

Examples​

Example 1: Implementing spaceToSend in a SimpleNetwork​

Excerpt from sst-elements/src/sst/elements/merlin/interfaces/linkControl.cc
bool LinkControl::spaceToSend(int vn, int bits) 
{
    if ( vn_remap_out[vn]->credits * flit_size < bits )
    {
        return false;
    }
    return true;
}

Example 2: Using spaceToSend in an Endpoint​

SimpleNetwork::Request *req = new SimpleNetwork::Request();
SST::Interfaces::StringEvent *strEv = new SST::Interfaces::StringEvent("hi!");
req->src = my_endpoint_id;
req->dest = a_destination_id;
req->size_in_bits = sizeof(strEv->getString()) * 8;
req->vn = vn;
req->givePayload(strEv);

if ( net_iface->spaceToSend(req->vn, req->num_bits) )
{
    // Do not need to check return value of send()
    // since we already checked that the request
    // can be accepted
    net_iface->send(req, req->vn);
}
#include <sst/core/interfaces/simpleNetwork.h>