Changes between Version 23 and Version 24 of user_applications

Timestamp:

Mar 31, 2016, 10:43:00 AM (10 years ago)

Author:

alain

Comment:

--

user_applications

@@ -39 +39 @@
 == __sort__ ==
 
-This first multi-threaded application is a very simple parallel sort. The input is an array of randomly generated integers. The size of this array is a parameter, that must be a multiple of the number of threads.
+This multi-threaded application is a very simple parallel sort. The input is an array of randomly generated integers. The size of this array is a parameter, that must be a multiple of the number of threads.
 
 It can run on a multi-processors, multi-clusters architecture, with one thread per processor core. 
@@ -202 +202 @@
 
 The source code can be found [source:soft/giet_vm/applications/router/router.c here], and the mapping is defined [source:soft/giet_vm/applications/router/router.py here].
+
+== __fft__ ==
+
+This multi-threaded parallel application is the port of the SPLASH FFT benchmark on the GIET_VM OS.
+
+It performs the in-place 1D Fast Fourier Transfom for an array of N complex points, using the Cooley-Tuckey method.
+The N data points are handled as a 2D array (rootN rows * rootN columns). This data array is implemented as
+distributed buffers (one buffer per cluster).
+ * The number of points N is defined by the M parameter  (N = 1<< M). It must be a power of 4.
+ * The number of threads is equal to the number of processors in the hardware architecture. It must be a power of 2. 
+ * The number of threads must be larger or equal to the number of rows (nthreads >= rootN).     
+Each thread is handling a subset of the  k of the rows (k = rootN / nthreads), and transpose the data array to benefit of cache locality.
+After the sequential initialization, the parallel processing is done in five steps separated by synchronisation barriers:
+ * first data array transpose
+ * FFT on the columns
+ * second data array transpose
+ * FFT on the rows
+ * third data array transpose
+The N input data points be initialised in three different modes:
+ * CONSTANT : all data points have the same [1,0] value
+ * COSIN    : data point n has [cos(n/N) , sin(n/N)] value
+ * RANDOM   : data points have pseudo random values
+The instrumentation results (computation times) are stored in a file.
+
+It requires one TTY terminal shared by all threads.
+
+The source code can be found [source:soft/giet_vm/applications/fft/fft.c here], and the mapping is defined [source:soft/giet_vm/applications/fft/fft.py here].
+