Tại thời điểm này, những nỗ lực của chúng tôi được tập trung trong việc thích nghi khuôn khổ DEWIZ để chạy trên một môi trường gridbased, bổ sung Sự kiện đồ thị trực quan, một lần trong chạy chế độ, một lần dừng lại chế độ Hình 5. VISWIZ mô-đun hiển thị thời gian thực hiện gửi và nhận các sự kiện | An Approach Toward MPI Applications in Wireless Networks 57 a lightweight and efficient mechanism Macias et al. 2004 to manage abrupt disconnections of computers with wireless interfaces. LAMGAC_Fault_detection function implements our software mechanism at the MPI application level. The mechanism is based on injecting ICMP Internet Control Message Protocol echo request packets from a specialized node to the wireless computers and monitoring echo replies. The injection is only made if LAMGAC_Fault_detection is invoked and enabled and replies determine the existence of an operational communication channel. This polling mechanism should not penalize the overall program execution. In order to reduce the overhead due to a long wait for a reply packet that would never arrive because of a channel failure an adaptive timeout mechanism is used. This timeout is calculated with the collected information by our WLAN monitoring tool Tonev et al. 2002 . 3. Unconstrained Global Optimization for n-Dimensional Functions One of the most interesting research areas in parallel nonlinear programming is that of finding the global minimum of a given function defined in a multidimensional space. The search uses a strategy based on a branch and bound methodology that recursively splits the initial search domain into smaller and smaller parts named boxes. The local search algorithm DFP Dahlquist and Bjorck 1974 starts from a defined number of random points. The box containing the smallest minimum so far and the boxes which contain a value next to the smallest minimum will be selected as the next domains to be explored. All the other boxes are deleted. These steps are repeated until the stopping criterion is satisfied. Parallel Program Without Wireless Channel State Detection A general scheme for the application is presented in Fig. 1. The master process Fig. is in charge of sending the boundaries of the domains to be explored in parallel in the current iteration in the first iteration .
