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POMPI, calloc and free:
 

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    <p>I'm trying to learn C and MPI, this program calculates the sum of n floats. But I have an error:</p> <p>/home/xx/PRIMO/primo.exe: free(): invalid next size (fast): 0x000000000109bda0 /home/xx/PRIMO/primo.exe: free(): invalid next size (fast): 0x00000000024fada0 </p> <p>Are 2 days that I don’t know which way to turn. Here the Program:</p> <pre><code>#include &lt;stdio.h&gt; #include &lt;stdlib.h&gt; #include &lt;string.h&gt; #include &lt;math.h&gt; #include "mpi.h" #define HOST 0 // prototypes void initialize( int argc, char *argv[] ); float *create_array( int n ); void data_scatter( float *numbers, float *numbers_loc, int packet_size, int rest ); void validations(); // global vars int menum, nproc, namelen; int main(int argc, char *argv[]) { initialize( argc, argv ); if( menum == HOST ) printf("Program started\n"); if( menum == HOST ) validations(); // ****** Declaring variebles ****** int n, tag, packet_size, rest, j, i; float *numbers, *numbers_loc; float sum = 0.0; numbers_loc = (float*) calloc( packet_size, sizeof (float) ); MPI_Status info; // ****** data distribution ****** scanf("%d", &amp;n); if( menum == HOST ) numbers = create_array( n ); MPI_Bcast( &amp;n, 1, MPI_INT, 0, MPI_COMM_WORLD ); double start_time = MPI_Wtime(); packet_size = n / nproc; rest = n % nproc; if( menum &lt; rest ) ++packet_size; data_scatter( numbers, numbers_loc, packet_size, rest ); // ****** partial sums, first level ****** for( j = 0; j &lt; packet_size; j++) { sum += numbers_loc[j]; } free(numbers_loc); // ****** iterating phase ****** for( i = 0; i &lt; log2(nproc); i++) { int pow1 = (int) pow(2, i); tag = pow1 + 15; if( (menum % pow1) == 0) { int pow2 = (int) pow(2,i+1); if( (menum % pow2) == 0 ) { float other_sum = 0; MPI_Recv( &amp;other_sum, 1, MPI_INT, menum + pow1, tag, MPI_COMM_WORLD, &amp;info ); sum += other_sum; } else { MPI_Send( &amp;sum, 1, MPI_INT, menum - pow1, tag, MPI_COMM_WORLD ); } } } // ****** printing result ****** if( menum == HOST ) { printf( "TOTAL SUM: %.2f\n", sum); } double end_time = MPI_Wtime(); double time = end_time - start_time; double max = 0; printf( "%d time %f\n", menum, time ); MPI_Reduce( &amp;time, &amp;max, 1, MPI_DOUBLE, MPI_MAX, 0, MPI_COMM_WORLD ); if(menum == HOST) printf( "%d max time %f\n", menum, max ); printf("Program terminated\n"); MPI_Finalize(); return 0; } void initialize( int argc, char *argv[] ) { MPI_Init(&amp;argc,&amp;argv); MPI_Comm_rank(MPI_COMM_WORLD,&amp;menum); MPI_Comm_size(MPI_COMM_WORLD,&amp;nproc); } float *create_array( int n ) { float sequenzial_sum = 0; int i; printf("Creating Array of dimension: %d\n", n); float *array = (float*) calloc( n, sizeof(float)); srand( time(NULL) ); for( i=0; i &lt; n; i++) { array[i] = ((float) rand())/ ((float) RAND_MAX); sequenzial_sum += array[i]; printf("-%f-", array[i]); } printf("\n"); printf("Array creation terminated, sum = %.2f \n", sequenzial_sum); return array; } void data_scatter( float *numbers, float *numbers_loc, int packet_size, int rest ) { MPI_Status info; int start = 0, offset = packet_size, i, tag; if( menum == HOST ) { memcpy(numbers_loc, numbers, packet_size * sizeof(float)); for( i=1; i &lt; nproc; i++ ) { start += offset; if( rest == i) --offset; tag = 22 + i; MPI_Send( &amp;numbers[start], offset, MPI_INT, i, tag, MPI_COMM_WORLD ); } free(numbers); } else { tag = 22 + menum; MPI_Recv( numbers_loc, packet_size, MPI_INT, 0, tag, MPI_COMM_WORLD, &amp;info ); } } void validations() { if( ( fmod(log2( nproc ), 1.0) != 0 )) { printf("CPU number must ne a power of 2\n"); MPI_Abort( MPI_COMM_WORLD, -1 ); } } </code></pre>
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