tools/pldt/org.eclipse.ptp.pldt.upc/html/upc_all_scatter.html

<h2>The <code>upc_all_scatter</code> function</h2>

<h4>Synopsis</h4>
<pre>    
    #include &lt;upc.h&gt;
    #include &lt;upc_collective.h&gt;
    void upc_all_scatter(shared void * restrict dst, 
                         shared const void * restrict src, 
                         size_t nbytes, 
                         upc_flag_t flags);
               
</pre>
<p>
<h4>Description</h4>
<p>
The <code>upc_all_scatter </code>  function 
copies the ith block of an area of shared
memory with affinity to a single thread to a block of shared memory with
affinity to the ith thread. The number of bytes in each block is <code>nbytes</code>.
<p><code>nbytes</code> must be strictly greater than 0.
<p>The <code>upc_all_scatter </code>  function treats the <code>src</code> pointer as if it pointed to a
shared memory area with the type:
<pre>
    shared [] char[nbytes * THREADS]
 </pre>
<p>and it treats the <code>dst</code> pointer as if it pointed to a shared memory area with
the type:
<pre>
    shared [nbytes] char[nbytes * THREADS]
</pre>
<p>The target of the <code>dst</code> pointer must have affinity to thread 0.
<p>The <code>dst</code> pointer is treated as if it has phase 0.
<p>For each thread i, the effect is equivalent to copying the ith block of <code>nbytes</code>
bytes pointed to by <code>src</code> to the block of <code>nbytes</code> bytes pointed to by 
<code>dst</code> that
has affinity to thread i.
<ul>
<li>EXAMPLE 1: <code>upc_all_scatter</code> for the dynamic THREADS translation environment.
<pre>
#include &lt;upc.h&gt;
#include &lt;upc_collective.h&gt;
#define NUMELEMS 10
#define SRC_THREAD 1
shared int *A;
shared [] int *myA, *srcA;
shared [NUMELEMS] int B[NUMELEMS*THREADS];
// allocate and initialize an array distributed across all threads
A = upc_all_alloc(THREADS, THREADS*NUMELEMS*sizeof(int));
myA = (shared [] int *) &A[MYTHREAD];
for (i=0; i<NUMELEMS*THREADS; i++)
myA[i] = i + NUMELEMS*THREADS*MYTHREAD; // (for example)
// scatter the SRC_THREADÕs row of the array
srcA = (shared [] int *) &A[SRC_THREAD];
upc_barrier;
upc_all_scatter( B, srcA, sizeof(int)*NUMELEMS,
UPC_IN_NOSYNC | UPC_OUT_NOSYNC);
upc_barrier;
</pre>
<li>EXAMPLE 2: <code>upc_all_scatter</code>  for the static THREADS translation environment.
<pre>
#include &lt;upc.h&gt;
#include &lt;upc_collective.h&gt;
#define NELEMS 10
shared [] int A[NELEMS*THREADS];
shared [NELEMS] int B[NELEMS*THREADS];
 
// Initialize A.
upc_all_scatter( B, A, sizeof(int)*NELEMS,
UPC_IN_ALLSYNC | UPC_OUT_ALLSYNC );
</pre>
 
</ul>
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