datatype_unpack.c

MPI stands for the Message Passing Interface. Written by the MPI Forum (a large committee comprising

                                            pData, pConv->count );
                DO_DEBUG( opal_output( 0, "4. unpack dest %p src %p length %lu\n",
                                       user_memory, packed_buffer, (unsigned long)remaining ); );
                MEMCPY_CSUM( user_memory, packed_buffer, remaining, pConv );
                user_memory += remaining;
            }
        }
        pConv->bConverted += bConverted;
    }
    *out_size = iov_count;
    *max_data = (pConv->bConverted - initial_bytes_converted);
    if( pConv->bConverted == pConv->local_size ) {
        pConv->flags |= CONVERTOR_COMPLETED;
        return 1;
    }
    return 0;
}

/**
 * This function handle partial types. Depending on the send operation it might happens
 * that we receive only a partial type (always predefined type). In fact the outcome is
 * that the unpack has to be done in 2 steps. As there is no way to know if the other
 * part of the datatype is already received, we need to use a trick to handle this special
 * case. The trick is to fill the missing part with some well known value, unpack the data
 * as if it was completely received, and then move into the user memory only the bytes
 * that don't match th wekk known value. This approach work as long as there is no need
 * for more than structural changes. They will not work for cases where we will have to
 * change the content of the data (as in all conversions that require changing the size
 * of the exponent or mantissa).
 */
static inline uint32_t
ompi_unpack_partial_datatype( ompi_convertor_t* pConvertor, dt_elem_desc_t* pElem,
                              char* partial_data,
                              ptrdiff_t start_position, ptrdiff_t end_position,
                              char** user_buffer )
{
    char unused_byte = 0x7F, saved_data[16];
    char temporary[16], *temporary_buffer = temporary;
    char* real_data = *user_buffer + pElem->elem.disp;
    uint32_t i, length, count_desc = 1;
    size_t data_length = ompi_ddt_basicDatatypes[pElem->elem.common.type]->size;

    DO_DEBUG( opal_output( 0, "unpack partial data start %d end %d data_length %lu user %p\n"
                           "\tbConverted %lu total_length %lu count %d\n",
                           start_position, end_position, (unsigned long)data_length, *user_buffer,
                           (unsigned long)pConvertor->bConverted, (unsigned long)pConvertor->local_size, pConvertor->count ); );

    /* Find a byte that is not used in the partial buffer */
 find_unused_byte:
    length = (uint32_t)(end_position - start_position);
    for( i = 0; i < length; i++ ) {
        if( unused_byte == partial_data[i] ) {
            unused_byte--;
            goto find_unused_byte;
        }
    }

    /* Copy and fill the rest of the buffer with the unused byte */
    memset( temporary, unused_byte, data_length );
    MEMCPY( temporary + start_position, partial_data, (end_position - start_position) );

    /* Save the content of the user memory */
    MEMCPY( saved_data, real_data, data_length );

    /* Then unpack the data into the user memory */
    UNPACK_PREDEFINED_DATATYPE( pConvertor, pElem, count_desc,
                                temporary_buffer, *user_buffer, data_length );

    /* reload the length as it is reset by the macro */
    data_length = ompi_ddt_basicDatatypes[pElem->elem.common.type]->size;

    /* For every occurence of the unused byte move data from the saved
     * buffer back into the user memory.
     */
    for( i = 0; i < data_length; i++ ) {
        if( unused_byte == real_data[i] )
            real_data[i] = saved_data[i];
    }
    return 0;
}

/* The pack/unpack functions need a cleanup. I have to create a proper interface to access
 * all basic functionalities, hence using them as basic blocks for all conversion functions.
 *
 * But first let's make some global assumptions:
 * - a datatype (with the flag DT_DATA set) will have the contiguous flags set if and only if
 *   the data is really contiguous (extent equal with size)
 * - for the DT_LOOP type the DT_CONTIGUOUS flag set means that the content of the loop is
 *   contiguous but with a gap in the begining or at the end.
 * - the DT_CONTIGUOUS flag for the type DT_END_LOOP is meaningless.
 */
int32_t
ompi_generic_simple_unpack_function( ompi_convertor_t* pConvertor,
                                     struct iovec* iov, uint32_t* out_size,
                                     size_t* max_data )
{
    dt_stack_t* pStack;                /* pointer to the position on the stack */
    uint32_t pos_desc;                 /* actual position in the description of the derived datatype */
    uint32_t count_desc;               /* the number of items already done in the actual pos_desc */
    uint16_t type = DT_MAX_PREDEFINED; /* type at current position */
    size_t total_unpacked = 0;         /* total size unpacked this time */
    dt_elem_desc_t* description;
    dt_elem_desc_t* pElem;
    const ompi_datatype_t *pData = pConvertor->pDesc;
    char *user_memory_base, *packed_buffer;
    size_t iov_len_local;
    uint32_t iov_count;

    DO_DEBUG( opal_output( 0, "ompi_convertor_generic_simple_unpack( %p, {%p, %lu}, %u )\n",
                           (void*)pConvertor, iov[0].iov_base, (unsigned long)iov[0].iov_len, *out_size ); );

    description = pConvertor->use_desc->desc;

    /* For the first step we have to add both displacement to the source. After in the
     * main while loop we will set back the source_base to the correct value. This is
     * due to the fact that the convertor can stop in the middle of a data with a count
     */
    pStack = pConvertor->pStack + pConvertor->stack_pos;
    pos_desc          = pStack->index;
    user_memory_base  = pConvertor->pBaseBuf + pStack->disp;
    count_desc        = (uint32_t)pStack->count;
    pStack--;
    pConvertor->stack_pos--;
    pElem = &(description[pos_desc]); 
    user_memory_base += pStack->disp;

    DO_DEBUG( opal_output( 0, "unpack start pos_desc %d count_desc %d disp %ld\n"
                           "stack_pos %d pos_desc %d count_desc %d disp %ld\n",
                           pos_desc, count_desc, (long)(user_memory_base - pConvertor->pBaseBuf),
                           pConvertor->stack_pos, pStack->index, (int)pStack->count, (long)(pStack->disp) ); );

    for( iov_count = 0; iov_count < (*out_size); iov_count++ ) {

        packed_buffer = iov[iov_count].iov_base;
        iov_len_local = iov[iov_count].iov_len;
        if( 0 != pConvertor->partial_length ) {
            size_t element_length = ompi_ddt_basicDatatypes[pElem->elem.common.type]->size;
            size_t missing_length = element_length - pConvertor->partial_length;

            assert( pElem->elem.common.flags & DT_FLAG_DATA );
            COMPUTE_CSUM( packed_buffer, missing_length, pConvertor );
            ompi_unpack_partial_datatype( pConvertor, pElem,
                                          packed_buffer,
                                          pConvertor->partial_length, element_length,
                                          &user_memory_base );
            --count_desc;
            if( 0 == count_desc ) {
                user_memory_base = pConvertor->pBaseBuf + pStack->disp;
                pos_desc++;  /* advance to the next data */
                UPDATE_INTERNAL_COUNTERS( description, pos_desc, pElem, count_desc );
            }
            packed_buffer += missing_length;
            iov_len_local -= missing_length;
            pConvertor->partial_length = 0;  /* nothing more inside */
        }
        while( 1 ) {
            while( pElem->elem.common.flags & DT_FLAG_DATA ) {
                /* now here we have a basic datatype */
                UNPACK_PREDEFINED_DATATYPE( pConvertor, pElem, count_desc,
                                            packed_buffer, user_memory_base, iov_len_local );
                if( 0 == count_desc ) {  /* completed */
                    user_memory_base = pConvertor->pBaseBuf + pStack->disp;
                    pos_desc++;  /* advance to the next data */
                    UPDATE_INTERNAL_COUNTERS( description, pos_desc, pElem, count_desc );
                    continue;
                }
                type = pElem->elem.common.type;
                assert( type < DT_MAX_PREDEFINED );
                if( 0 != iov_len_local ) {
                    char* temp = user_memory_base;
                    /* We have some partial data here. Let's copy it into the convertor
                     * and keep it hot until the next round.
                     */
                    assert( iov_len_local < ompi_ddt_basicDatatypes[type]->size );
                    COMPUTE_CSUM( packed_buffer, iov_len_local, pConvertor );

                    ompi_unpack_partial_datatype( pConvertor, pElem,
                                                  packed_buffer, 0, iov_len_local,
                                                  &temp );

                    pConvertor->partial_length = (uint32_t)iov_len_local;
                    iov_len_local = 0;
                }
                goto complete_loop;
            }
            if( DT_END_LOOP == pElem->elem.common.type ) { /* end of the current loop */
                DO_DEBUG( opal_output( 0, "unpack end_loop count %d stack_pos %d pos_desc %d disp %ld space %lu\n",
                                       (int)pStack->count, pConvertor->stack_pos, pos_desc,
                                      (long)pStack->disp, (unsigned long)iov_len_local ); );
                if( --(pStack->count) == 0 ) { /* end of loop */
                    if( pConvertor->stack_pos == 0 ) {
                        /* Force the conversion to stop by lowering the number of iovecs. */
                        *out_size = iov_count;
                        goto complete_loop;  /* completed */
                    }
                    pConvertor->stack_pos--;
                    pStack--;
                    pos_desc++;
                } else {
                    pos_desc = pStack->index + 1;
                    if( pStack->index == -1 ) {
                        pStack->disp += (pData->ub - pData->lb);
                    } else {
                        assert( DT_LOOP == description[pStack->index].loop.common.type );
                        pStack->disp += description[pStack->index].loop.extent;
                    }
                }
                user_memory_base = pConvertor->pBaseBuf + pStack->disp;
                UPDATE_INTERNAL_COUNTERS( description, pos_desc, pElem, count_desc );
                DO_DEBUG( opal_output( 0, "unpack new_loop count %d stack_pos %d pos_desc %d disp %ld space %lu\n",
                                       (int)pStack->count, pConvertor->stack_pos, pos_desc,
                                       (long)pStack->disp, (unsigned long)iov_len_local ); );
            }
            if( DT_LOOP == pElem->elem.common.type ) {
                ptrdiff_t local_disp = (ptrdiff_t)user_memory_base;
                if( pElem->loop.common.flags & DT_FLAG_CONTIGUOUS ) {
                    UNPACK_CONTIGUOUS_LOOP( pConvertor, pElem, count_desc, 
                                            packed_buffer, user_memory_base, iov_len_local );
                    if( 0 == count_desc ) {  /* completed */
                        pos_desc += pElem->loop.items + 1;
                        goto update_loop_description;
                    }
                    /* Save the stack with the correct last_count value. */
                }
                local_disp = (ptrdiff_t)user_memory_base - local_disp;
                PUSH_STACK( pStack, pConvertor->stack_pos, pos_desc, DT_LOOP, count_desc,
                            pStack->disp + local_disp);
                pos_desc++;
            update_loop_description:  /* update the current state */
                user_memory_base = pConvertor->pBaseBuf + pStack->disp;
                UPDATE_INTERNAL_COUNTERS( description, pos_desc, pElem, count_desc );
                DDT_DUMP_STACK( pConvertor->pStack, pConvertor->stack_pos, pElem, "advance loop" );
                continue;
            }
        }
    complete_loop:
        iov[iov_count].iov_len -= iov_len_local;  /* update the amount of valid data */
        total_unpacked += iov[iov_count].iov_len;
    }
    *max_data = total_unpacked;
    pConvertor->bConverted += total_unpacked;  /* update the already converted bytes */
    *out_size = iov_count;
    if( pConvertor->bConverted == pConvertor->remote_size ) {
        pConvertor->flags |= CONVERTOR_COMPLETED;
        return 1;
    }
    /* I complete an element, next step I should go to the next one */
    PUSH_STACK( pStack, pConvertor->stack_pos, pos_desc, DT_BYTE, count_desc,
                user_memory_base - pStack->disp - pConvertor->pBaseBuf );
    DO_DEBUG( opal_output( 0, "unpack save stack stack_pos %d pos_desc %d count_desc %d disp %ld\n",
                           pConvertor->stack_pos, pStack->index, (int)pStack->count, (long)pStack->disp ); );
    return 0;
}