I try to perform an asynchronous data transfer to an Intel Xeon Phi. Note that asynchronous computation works as expected. If I try to combine data transfer and computation (in an offload statement) timing indicates that the data transfer is done synchronously while the following computation is done asynchronously.
A test example that illustrates the point is given below. The output is
0.928997 0.288048
which indicates that almost a second is spend in the asynchronous call while only 0.28 seconds are spend in waiting for that asynchronous call.
Any help would be appreciated.
#include <stdlib.h>
#include <iostream>
using namespace std;
#include "timer.hpp"
#define ALLOC alloc_if(1)
#define FREE free_if(1)
#define RETAIN free_if(0)
#define REUSE alloc_if(0)
int main() {
int n = 1000*1000*100;
double *p = (double*)malloc(sizeof(double)*n);
int rep = 10;
#pragma offload target(mic:0) in(p:length(n) ALLOC RETAIN)
{}
timer t1, t2;
for(int i=0;i<rep;i++) {
t1.start();
#pragma offload_transfer target(mic:0) out(p:length(n) REUSE RETAIN) signal(p)
/* This works as expected
#pragma offload_transfer target(mic:0) signal(p)
{ usleep(2e6); }
*/
t1.stop();
t2.start();
#pragma offload_transfer target(mic:0) wait(p)
t2.stop();
}
cout << t1.total() << ""<< t2.total() << endl;
#pragma offload target(mic:0) nocopy(p:length(n) REUSE FREE)
{}
}The hardware seems to work properly
MicCheck 3.4.3-r1 Copyright 2013 Intel Corporation All Rights Reserved Executing default tests for host Test 0: Check number of devices the OS sees in the system ... pass Test 1: Check mic driver is loaded ... pass Test 2: Check number of devices driver sees in the system ... pass Test 3: Check mpssd daemon is running ... pass Executing default tests for device: 0 Test 4 (mic0): Check device is in online state and its postcode is FF ... pass Test 5 (mic0): Check ras daemon is available in device ... pass Test 6 (mic0): Check running flash version is correct ... pass Test 7 (mic0): Check running SMC firmware version is correct ... pass Status: OK