Professores

Simple offloaded code, enormous time consuming

Dear all,

I recently started using Xeon Phi cards for parallel programming, so I am still a newbie in this field.

I wrote this code as a simple example to start understanding this fascinating world, but I got surprised when I looked at the time of executions.

When I run the code on the host, execution time is 0,08 s. When I run the code adding the pragma offload and pragma omp parallel for, execution time increase up to 9s!

When I compiled the codes, I used -O3 optimization for both of them.

Is there something I am missing?

 

SLES11sp3 + MPSS 3.4.3 + MOFED 2.3.2.0.0.1 IB scif issues

Hello,

We have a number of iDataPlex dx360 M4 Server machines with each 2 Xeon Phi Coprocessor 5110P cards, and one Mellanox ConnectX-3 card. We're running SLES 11sp3 linux on these machines using a 3.0.101-0.40-default kernel. I've installed mpss 3.4.3, updated the firmware and almost everything seems to function.

The only problem I encounter is with infiniband.

The Last Line Effect

Copy-Paste

I have studied numbers of errors caused by using the Copy-Paste method and can assure you that programmers most often tend to make mistakes in the last fragment of a homogeneous code block. I have never seen this phenomenon described in books on programming, so I decided to write about it myself. I called it the "last line effect".

Unix Signal Handling (Xeon-phi)

Hello,

I am porting a code to Xeon Phi (using manual offload) in C++ and I am trying to catch SIGINT signal to free correctly memory before stopping the program. This program also uses openMP tasks for asynchronous I/O.

My first goal is to ignore the SIGINT signal with the function sigaction and the macro SIG_IGN. Unfortunately, my program can still be stopped by a Ctrl C. I also tried to block the SIGINT signal (with pthread_sigmask) before the omp parallel region and catch this signal in the master thread only but without success.   

Odd behaviour regarding execution time vs number of threads

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Hello,
 

While porting an image processing library to the Xeon Phi, I stumbled upon a strange behaviour: the processing is about 20% faster when I set the number of threads to precisely 103 (I ran the processing multiple times using between 95 and 118 threads).
 

Connecting coprocessor to bridge to communicate with internet

Hello,

I am running Ubuntu 14.04 with a xeon phi 31s1p and I have been trying to set up a bridge so that I can have the phi access the internet, although I have been having a lot of trouble and can't seem to figure out what's wrong. I'm pretty sure the bridge itself is fine but the phi can't connect to it, anytime I try and use the simple command for it to connect to the bridge it gives this:

/var/mpss/mic0/etc/network# micctrl --network=static --bridge=br0 --ip=172.31.1.1
  [Error] br0: Failed - required brctl command not installed

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