Exemple #1
0
/**
    Purpose
    -------
    SGETRF computes an LU factorization of a general M-by-N matrix A
    using partial pivoting with row interchanges.

    The factorization has the form
        A = P * L * U
    where P is a permutation matrix, L is lower triangular with unit
    diagonal elements (lower trapezoidal if m > n), and U is upper
    triangular (upper trapezoidal if m < n).

    This is the right-looking Level 3 BLAS version of the algorithm.

    Arguments
    ---------
    @param[in]
    ngpu    INTEGER
            Number of GPUs to use. ngpu > 0.

    @param[in]
    m       INTEGER
            The number of rows of the matrix A.  M >= 0.

    @param[in]
    n       INTEGER
            The number of columns of the matrix A.  N >= 0.

    @param[in,out]
    d_lA    REAL array of pointers on the GPU, dimension (ngpu).
            On entry, the M-by-N matrix A distributed over GPUs
            (d_lA[d] points to the local matrix on d-th GPU).
            It uses 1D block column cyclic format with the block size of nb,
            and each local matrix is stored by column.
            On exit, the factors L and U from the factorization
            A = P*L*U; the unit diagonal elements of L are not stored.

    @param[in]
    ldda     INTEGER
            The leading dimension of the array d_lA.  LDDA >= max(1,M).

    @param[out]
    ipiv    INTEGER array, dimension (min(M,N))
            The pivot indices; for 1 <= i <= min(M,N), row i of the
            matrix was interchanged with row IPIV(i).

    @param[out]
    info    INTEGER
      -     = 0:  successful exit
      -     < 0:  if INFO = -i, the i-th argument had an illegal value
                  or another error occured, such as memory allocation failed.
      -     > 0:  if INFO = i, U(i,i) is exactly zero. The factorization
                  has been completed, but the factor U is exactly
                  singular, and division by zero will occur if it is used
                  to solve a system of equations.

    @ingroup magma_sgesv_comp
    ********************************************************************/
extern "C" magma_int_t
magma_sgetrf_mgpu(
    magma_int_t ngpu,
    magma_int_t m, magma_int_t n,
    magmaFloat_ptr d_lA[], magma_int_t ldda, magma_int_t *ipiv,
    magma_int_t *info)
{
    magma_int_t nb, n_local[MagmaMaxGPUs];
    magma_int_t maxm;
    magma_int_t i, j, d, lddat, lddwork;
    float *d_lAT[MagmaMaxGPUs];
    float *d_panel[MagmaMaxGPUs], *work;
    magma_queue_t queues[MagmaMaxGPUs][2];

    /* Check arguments */
    *info = 0;
    if (m < 0)
        *info = -2;
    else if (n < 0)
        *info = -3;
    else if (ldda < max(1,m))
        *info = -5;

    if (*info != 0) {
        magma_xerbla( __func__, -(*info) );
        return *info;
    }

    /* Quick return if possible */
    if (m == 0 || n == 0)
        return *info;

    /* create the queues */
    for( d=0; d < ngpu; d++ ) {
        magma_queue_create( d, &queues[d][0] );
        magma_queue_create( d, &queues[d][1] );
    }

    /* Function Body */
    nb = magma_get_sgetrf_nb( m, n );

    if (nb <= 1 || nb >= n) {
        /* Use CPU code. */
        magma_smalloc_cpu( &work, m * n );
        if ( work == NULL ) {
            *info = MAGMA_ERR_HOST_ALLOC;
            return *info;
        }
        magma_sgetmatrix( m, n, d_lA[0], ldda, work, m, queues[0][0] );
        lapackf77_sgetrf(&m, &n, work, &m, ipiv, info);
        magma_ssetmatrix( m, n, work, m, d_lA[0], ldda, queues[0][0] );
        magma_free_cpu(work);
    } else {
        /* Use hybrid blocked code. */
        magma_device_t orig_dev;
        magma_getdevice( &orig_dev );
        
        maxm = magma_roundup( m, 32 );
        if ( ngpu > ceil((float)n/nb) ) {
            printf( " * too many GPUs for the matrix size, using %d GPUs\n", (int) ngpu );
            *info = -1;
            return *info;
        }

        /* allocate workspace for each GPU */
        lddat = magma_roundup( ((magma_ceildiv( n, nb )/ngpu)*nb), 32 );
        lddat = magma_ceildiv( n, nb );        /* number of block columns         */
        lddat = magma_ceildiv( lddat, ngpu );  /* number of block columns per GPU */
        lddat = nb*lddat;                      /* number of columns per GPU       */
        lddat = magma_roundup( lddat, 32 );    /* make it a multiple of 32        */
        for (i=0; i < ngpu; i++) {
            magma_setdevice(i);
            
            /* local-n and local-ld */
            n_local[i] = ((n/nb)/ngpu)*nb;
            if (i < (n/nb)%ngpu)
                n_local[i] += nb;
            else if (i == (n/nb)%ngpu)
                n_local[i] += n%nb;
            
            /* workspaces */
            if (MAGMA_SUCCESS != magma_smalloc( &d_panel[i], (3+ngpu)*nb*maxm )) {
                for( j=0; j <= i; j++ ) {
                    magma_setdevice(j);
                }
                for( j=0; j < i; j++ ) {
                    magma_setdevice(j);
                    magma_free( d_panel[j] );
                    magma_free( d_lAT[j]   );
                }
                *info = MAGMA_ERR_DEVICE_ALLOC;
                return *info;
            }
            
            /* local-matrix storage */
            if (MAGMA_SUCCESS != magma_smalloc( &d_lAT[i], lddat*maxm )) {
                for( j=0; j <= i; j++ ) {
                    magma_setdevice(j);
                    magma_free( d_panel[j] );
                }
                for( j=0; j < i; j++ ) {
                    magma_setdevice(j);
                    magma_free( d_lAT[j] );
                }
                *info = MAGMA_ERR_DEVICE_ALLOC;
                return *info;
            }
            
            magmablas_stranspose( m, n_local[i], d_lA[i], ldda, d_lAT[i], lddat, queues[i][1] );
        }
        for (i=0; i < ngpu; i++) {
            magma_setdevice(i);
            magma_queue_sync(queues[i][0]);
        }
        magma_setdevice(0);

        /* cpu workspace */
        lddwork = maxm;
        if (MAGMA_SUCCESS != magma_smalloc_pinned( &work, lddwork*nb*ngpu )) {
            for (i=0; i < ngpu; i++ ) {
                magma_setdevice(i);
                magma_free( d_panel[i] );
                magma_free( d_lAT[i]   );
            }
            *info = MAGMA_ERR_HOST_ALLOC;
            return *info;
        }

        /* calling multi-gpu interface with allocated workspaces and queues */
        magma_sgetrf2_mgpu(ngpu, m, n, nb, 0, d_lAT, lddat, ipiv, d_panel, work, maxm,
                           queues, info);

        /* clean up */
        for( d=0; d < ngpu; d++ ) {
            magma_setdevice(d);
            
            /* save on output */
            magmablas_stranspose( n_local[d], m, d_lAT[d], lddat, d_lA[d], ldda, queues[d][0] );
            magma_queue_sync(queues[d][0]);
            magma_queue_sync(queues[d][1]);

            magma_free( d_lAT[d]   );
            magma_free( d_panel[d] );
        } /* end of for d=1,..,ngpu */
        magma_setdevice( orig_dev );
        magma_free_pinned( work );
    }

    /* clean up */
    for( d=0; d < ngpu; d++ ) {
        magma_setdevice(d);
        magma_queue_destroy( queues[d][0] );
        magma_queue_destroy( queues[d][1] );
    }

    return *info;
}
Exemple #2
0
/**
    Purpose
    -------
    SGETRF_m computes an LU factorization of a general M-by-N matrix A
    using partial pivoting with row interchanges.  This version does not
    require work space on the GPU passed as input. GPU memory is allocated
    in the routine. The matrix may exceed the GPU memory.

    The factorization has the form
       A = P * L * U
    where P is a permutation matrix, L is lower triangular with unit
    diagonal elements (lower trapezoidal if m > n), and U is upper
    triangular (upper trapezoidal if m < n).

    This is the right-looking Level 3 BLAS version of the algorithm.

    Note: The factorization of big panel is done calling multiple-gpu-interface.
    Pivots are applied on GPU within the big panel.

    Arguments
    ---------
    @param[in]
    num_gpus INTEGER
             The number of GPUs.  num_gpus > 0.

    @param[in]
    m       INTEGER
            The number of rows of the matrix A.  M >= 0.

    @param[in]
    n       INTEGER
            The number of columns of the matrix A.  N >= 0.

    @param[in,out]
    A       REAL array, dimension (LDA,N)
            On entry, the M-by-N matrix to be factored.
            On exit, the factors L and U from the factorization
            A = P*L*U; the unit diagonal elements of L are not stored.
    \n
            Higher performance is achieved if A is in pinned memory, e.g.
            allocated using magma_malloc_pinned.

    @param[in]
    lda     INTEGER
            The leading dimension of the array A.  LDA >= max(1,M).

    @param[out]
    ipiv    INTEGER array, dimension (min(M,N))
            The pivot indices; for 1 <= i <= min(M,N), row i of the
            matrix was interchanged with row IPIV(i).

    @param[out]
    info    INTEGER
      -     = 0:  successful exit
      -     < 0:  if INFO = -i, the i-th argument had an illegal value
                  or another error occured, such as memory allocation failed.
      -     > 0:  if INFO = i, U(i,i) is exactly zero. The factorization
                  has been completed, but the factor U is exactly
                  singular, and division by zero will occur if it is used
                  to solve a system of equations.

    @ingroup magma_sgesv_comp
    ********************************************************************/
extern "C" magma_int_t
magma_sgetrf_m(magma_int_t num_gpus, magma_int_t m, magma_int_t n,
               float *A, magma_int_t lda,
               magma_int_t *ipiv, magma_int_t *info)
{
#define     A(i,j) (A      + (j)*lda + (i))
#define dAT(d,i,j) (dAT[d] + (i)*nb*ldn_local + (j)*nb)
#define dPT(d,i,j) (dPT[d] + (i)*nb*nb + (j)*nb*maxm)

    magma_timer_t time=0, time_total=0, time_alloc=0, time_set=0, time_get=0, time_comp=0;
    timer_start( time_total );
    real_Double_t flops;

    float c_one     = MAGMA_S_ONE;
    float c_neg_one = MAGMA_S_NEG_ONE;
    float *dAT[MagmaMaxGPUs], *dA[MagmaMaxGPUs], *dPT[MagmaMaxGPUs];
    magma_int_t        iinfo = 0, nb, nbi, maxm, n_local[MagmaMaxGPUs], ldn_local;
    magma_int_t        N, M, NB, NBk, I, d, num_gpus0 = num_gpus;
    magma_int_t        ii, jj, h, offset, ib, rows, s;
    
    magma_queue_t stream[MagmaMaxGPUs][2];
    magma_event_t  event[MagmaMaxGPUs][2];

    *info = 0;
    if (m < 0)
        *info = -1;
    else if (n < 0)
        *info = -2;
    else if (lda < max(1,m))
        *info = -4;

    if (*info != 0) {
        magma_xerbla( __func__, -(*info) );
        return *info;
    }

    /* Quick return if possible */
    if (m == 0 || n == 0)
        return *info;

    magma_device_t orig_dev;
    magma_getdevice( &orig_dev );
    magma_queue_t orig_stream;
    magmablasGetKernelStream( &orig_stream );
    
    /* initialize nb */
    nb = magma_get_sgetrf_nb(m);
    maxm = ((m  + 31)/32)*32;

    /* figure out NB */
    size_t freeMem, totalMem;
    cudaMemGetInfo( &freeMem, &totalMem );
    freeMem /= sizeof(float);
    
    /* number of columns in the big panel */
    h = 1+(2+num_gpus0);
    NB = (magma_int_t)(0.8*freeMem/maxm-h*nb);
    const char* ngr_nb_char = getenv("MAGMA_NGR_NB");
    if ( ngr_nb_char != NULL )
        NB = max( nb, min( NB, atoi(ngr_nb_char) ) );
    //NB = 5*max(nb,32);

    if ( num_gpus0 > ceil((float)NB/nb) ) {
        num_gpus = (int)ceil((float)NB/nb);
        h = 1+(2+num_gpus);
        NB = (magma_int_t)(0.8*freeMem/maxm-h*nb);
    } else {
        num_gpus = num_gpus0;
    }
    if ( num_gpus*NB >= n ) {
        #ifdef CHECK_SGETRF_OOC
        printf( "      * still fit in GPU memory.\n" );
        #endif
        NB = n;
    } else {
        #ifdef CHECK_SGETRF_OOC
        printf( "      * don't fit in GPU memory.\n" );
        #endif
        NB = num_gpus*NB;
        NB = max( nb, (NB / nb) * nb); /* making sure it's devisable by nb (x64) */
    }

    #ifdef CHECK_SGETRF_OOC
    if ( NB != n ) printf( "      * running in out-core mode (n=%d, NB=%d, nb=%d, freeMem=%.2e).\n", n, NB, nb, (float)freeMem );
    else           printf( "      * running in in-core mode  (n=%d, NB=%d, nb=%d, freeMem=%.2e).\n", n, NB, nb, (float)freeMem );
    #endif

    if ( (nb <= 1) || (nb >= min(m,n)) ) {
        /* Use CPU code for scalar of one tile. */
        lapackf77_sgetrf(&m, &n, A, &lda, ipiv, info);
    } else {
        /* Use hybrid blocked code. */

        /* allocate memory on GPU to store the big panel */
        timer_start( time_alloc );
        n_local[0] = (NB/nb)/num_gpus;
        if ( NB%(nb*num_gpus) != 0 )
            n_local[0]++;
        n_local[0] *= nb;
        ldn_local = ((n_local[0]+31)/32)*32;
    
        for( d=0; d < num_gpus; d++ ) {
            magma_setdevice(d);
            if (MAGMA_SUCCESS != magma_smalloc( &dA[d], (ldn_local+h*nb)*maxm )) {
                *info = MAGMA_ERR_DEVICE_ALLOC;
                return *info;
            }
            dPT[d] = dA[d] + nb*maxm;      /* for storing the previous panel from CPU */
            dAT[d] = dA[d] + h*nb*maxm;    /* for storing the big panel               */
            magma_queue_create( &stream[d][0] );
            magma_queue_create( &stream[d][1] );
            magma_event_create( &event[d][0] );
            magma_event_create( &event[d][1] );
        }
        //magma_setdevice(0);
        timer_stop( time_alloc );
        
        for( I=0; I < n; I += NB ) {
            M = m;
            N = min( NB, n-I );       /* number of columns in this big panel             */
            s = min( max(m-I,0), N )/nb; /* number of small block-columns in this big panel */
    
            maxm = ((M + 31)/32)*32;
            if ( num_gpus0 > ceil((float)N/nb) ) {
                num_gpus = (int)ceil((float)N/nb);
            } else {
                num_gpus = num_gpus0;
            }
    
            for( d=0; d < num_gpus; d++ ) {
                n_local[d] = ((N/nb)/num_gpus)*nb;
                if (d < (N/nb)%num_gpus)
                    n_local[d] += nb;
                else if (d == (N/nb)%num_gpus)
                    n_local[d] += N%nb;
            }
            ldn_local = ((n_local[0]+31)/32)*32;
            
            /* upload the next big panel into GPU, transpose (A->A'), and pivot it */
            timer_start( time );
            magmablas_ssetmatrix_transpose_mgpu(num_gpus, stream, A(0,I), lda,
                                                dAT, ldn_local, dA, maxm, M, N, nb);
            for( d=0; d < num_gpus; d++ ) {
                magma_setdevice(d);
                magma_queue_sync( stream[d][0] );
                magma_queue_sync( stream[d][1] );
            magmablasSetKernelStream(NULL);
            }
            time_set += timer_stop( time );
    
            timer_start( time );
            /* == --------------------------------------------------------------- == */
            /* == loop around the previous big-panels to update the new big-panel == */
            for( offset = 0; offset < min(m,I); offset += NB ) {
                NBk = min( m-offset, NB );
                /* start sending the first tile from the previous big-panels to gpus */
                for( d=0; d < num_gpus; d++ ) {
                    magma_setdevice(d);
                    nbi  = min( nb, NBk );
                    magma_ssetmatrix_async( (M-offset), nbi,
                                            A(offset,offset), lda,
                                            dA[d],            (maxm-offset), stream[d][0] );
                    
                    /* make sure the previous update finished */
                    magmablasSetKernelStream(stream[d][0]);
                    //magma_queue_sync( stream[d][1] );
                    magma_queue_wait_event( stream[d][0], event[d][0] );
                    
                    /* transpose */
                    magmablas_stranspose( M-offset, nbi, dA[d], maxm-offset, dPT(d,0,0), nb );
                }
                
                /* applying the pivot from the previous big-panel */
                for( d=0; d < num_gpus; d++ ) {
                    magma_setdevice(d);
                    magmablasSetKernelStream(stream[d][1]);
                    magmablas_spermute_long3( dAT(d,0,0), ldn_local, ipiv, NBk, offset );
                }
                
                /* == going through each block-column of previous big-panels == */
                for( jj=0, ib=offset/nb; jj < NBk; jj += nb, ib++ ) {
                    ii   = offset+jj;
                    rows = maxm - ii;
                    nbi  = min( nb, NBk-jj );
                    for( d=0; d < num_gpus; d++ ) {
                        magma_setdevice(d);
                        
                        /* wait for a block-column on GPU */
                        magma_queue_sync( stream[d][0] );
                        
                        /* start sending next column */
                        if ( jj+nb < NBk ) {
                            magma_ssetmatrix_async( (M-ii-nb), min(nb,NBk-jj-nb),
                                                    A(ii+nb,ii+nb), lda,
                                                    dA[d],          (rows-nb), stream[d][0] );
                            
                            /* make sure the previous update finished */
                            magmablasSetKernelStream(stream[d][0]);
                            //magma_queue_sync( stream[d][1] );
                            magma_queue_wait_event( stream[d][0], event[d][(1+jj/nb)%2] );
                            
                            /* transpose next column */
                            magmablas_stranspose( M-ii-nb, nb, dA[d], rows-nb, dPT(d,0,(1+jj/nb)%2), nb );
                        }
                        
                        /* update with the block column */
                        magmablasSetKernelStream(stream[d][1]);
                        magma_strsm( MagmaRight, MagmaUpper, MagmaNoTrans, MagmaUnit,
                                     n_local[d], nbi, c_one, dPT(d,0,(jj/nb)%2), nb, dAT(d,ib,0), ldn_local );
                        if ( M > ii+nb ) {
                            magma_sgemm( MagmaNoTrans, MagmaNoTrans,
                                n_local[d], M-(ii+nb), nbi, c_neg_one, dAT(d,ib,0), ldn_local,
                                dPT(d,1,(jj/nb)%2), nb, c_one, dAT(d,ib+1,0), ldn_local );
                        }
                        magma_event_record( event[d][(jj/nb)%2], stream[d][1] );
                    
                    } /* end of for each block-columns in a big-panel */
                }
            } /* end of for each previous big-panels */
            for( d=0; d < num_gpus; d++ ) {
                magma_setdevice(d);
                magma_queue_sync( stream[d][0] );
                magma_queue_sync( stream[d][1] );
            magmablasSetKernelStream(NULL);
            }
    
            /* calling magma-gpu interface to panel-factorize the big panel */
            if ( M > I ) {
                //magma_sgetrf1_mgpu(num_gpus, M-I, N, nb, I, dAT, ldn_local, ipiv+I, dA, A(0,I), lda,
                //                   (magma_queue_t **)stream, &iinfo);
                magma_sgetrf2_mgpu(num_gpus, M-I, N, nb, I, dAT, ldn_local, ipiv+I, dA, A(0,I), lda,
                                   stream, &iinfo);
                if ( iinfo < 0 ) {
                    *info = iinfo;
                    break;
                } else if ( iinfo != 0 ) {
                    *info = iinfo + I * NB;
                    //break;
                }
                /* adjust pivots */
                for( ii=I; ii < min(I+N,m); ii++ )
                    ipiv[ii] += I;
            }
            time_comp += timer_stop( time );
    
            /* download the current big panel to CPU */
            timer_start( time );
            magmablas_sgetmatrix_transpose_mgpu(num_gpus, stream, dAT, ldn_local, A(0,I), lda, dA, maxm, M, N, nb);
            for( d=0; d < num_gpus; d++ ) {
                magma_setdevice(d);
                magma_queue_sync( stream[d][0] );
                magma_queue_sync( stream[d][1] );
            magmablasSetKernelStream(NULL);
            }
            time_get += timer_stop( time );
        } /* end of for */
    
        timer_stop( time_total );
        flops = FLOPS_SGETRF( m, n ) / 1e9;
        timer_printf(" memory-allocation time: %e\n", time_alloc );
        timer_printf(" NB=%d nb=%d\n", (int) NB, (int) nb );
        timer_printf(" memcopy and transpose %e seconds\n", time_set );
        timer_printf(" total time %e seconds\n", time_total );
        timer_printf(" Performance %f GFlop/s, %f seconds without htod and dtoh\n",     flops / (time_comp),               time_comp               );
        timer_printf(" Performance %f GFlop/s, %f seconds with    htod\n",              flops / (time_comp + time_set),    time_comp + time_set    );
        timer_printf(" Performance %f GFlop/s, %f seconds with    dtoh\n",              flops / (time_comp + time_get),    time_comp + time_get    );
        timer_printf(" Performance %f GFlop/s, %f seconds without memory-allocation\n", flops / (time_total - time_alloc), time_total - time_alloc );
    
        for( d=0; d < num_gpus0; d++ ) {
            magma_setdevice(d);
            magma_free( dA[d] );
            magma_event_destroy( event[d][0] );
            magma_event_destroy( event[d][1] );
            magma_queue_destroy( stream[d][0] );
            magma_queue_destroy( stream[d][1] );
        }
        magma_setdevice( orig_dev );
        magmablasSetKernelStream( orig_stream );
    }
    if ( *info >= 0 )
        magma_sgetrf_piv(m, n, NB, A, lda, ipiv, info);
    return *info;
} /* magma_sgetrf_m */
Exemple #3
0
extern "C" magma_err_t
magma_sgetrf_mgpu(magma_int_t num_gpus,
                  magma_int_t m, magma_int_t n,
                  magmaFloat_ptr *d_lA, size_t dlA_offset, magma_int_t ldda,
                  magma_int_t *ipiv, magma_int_t *info,
                  magma_queue_t *queues)
{
    /*  -- clMAGMA (version 1.1.0) --
           Univ. of Tennessee, Knoxville
           Univ. of California, Berkeley
           Univ. of Colorado, Denver
           @date January 2014

        Purpose
        =======

        SGETRF computes an LU factorization of a general M-by-N matrix A
        using partial pivoting with row interchanges.

        The factorization has the form
           A = P * L * U
        where P is a permutation matrix, L is lower triangular with unit
        diagonal elements (lower trapezoidal if m > n), and U is upper
        triangular (upper trapezoidal if m < n).

        This is the right-looking Level 3 BLAS version of the algorithm.

        Arguments
        =========

        NUM_GPUS
                (input) INTEGER
                The number of GPUS to be used for the factorization.

        M       (input) INTEGER
                The number of rows of the matrix A.  M >= 0.

        N       (input) INTEGER
                The number of columns of the matrix A.  N >= 0.

        A       (input/output) REAL array on the GPU, dimension (LDDA,N).
                On entry, the M-by-N matrix to be factored.
                On exit, the factors L and U from the factorization
                A = P*L*U; the unit diagonal elements of L are not stored.

        LDDA     (input) INTEGER
                The leading dimension of the array A.  LDDA >= max(1,M).

        IPIV    (output) INTEGER array, dimension (min(M,N))
                The pivot indices; for 1 <= i <= min(M,N), row i of the
                matrix was interchanged with row IPIV(i).

        INFO    (output) INTEGER
                = 0:  successful exit
                < 0:  if INFO = -i, the i-th argument had an illegal value
                      or another error occured, such as memory allocation failed.
                > 0:  if INFO = i, U(i,i) is exactly zero. The factorization
                      has been completed, but the factor U is exactly
                      singular, and division by zero will occur if it is used
                      to solve a system of equations.
        =====================================================================    */


    float c_one     = MAGMA_S_ONE;
    float c_neg_one = MAGMA_S_NEG_ONE;

    magma_int_t iinfo, nb, n_local[MagmaMaxGPUs];
    magma_int_t maxm, mindim;
    magma_int_t i, j, d, rows, cols, s, lddat, lddwork;
    magma_int_t id, i_local, i_local2, nb0, nb1;
    magmaFloat_ptr d_lAT[MagmaMaxGPUs];
    magmaFloat_ptr d_panel[MagmaMaxGPUs];
    float *work;

    /* Check arguments */
    *info = 0;
    if (m < 0)
        *info = -2;
    else if (n < 0)
        *info = -3;
    else if (ldda < max(1,m))
        *info = -5;

    if (*info != 0) {
        magma_xerbla( __func__, -(*info) );
        return *info;
    }

    /* Quick return if possible */
    if (m == 0 || n == 0)
        return *info;

    /* Function Body */
    mindim = min(m, n);
    nb     = magma_get_sgetrf_nb(m);

    if (nb <= 1 || nb >= n) {
        /* Use CPU code. */
        magma_smalloc_cpu( &work, m * n );
        if ( work == NULL ) {
            *info = MAGMA_ERR_HOST_ALLOC;
            return *info;
        }
        magma_sgetmatrix( m, n, d_lA[0], 0, ldda, work, 0, m, queues[0] );
        lapackf77_sgetrf(&m, &n, work, &m, ipiv, info);
        magma_ssetmatrix( m, n, work, 0, m, d_lA[0], 0, ldda, queues[0] );
        magma_free_cpu(work);
    } else {
        /* Use hybrid blocked code. */
        maxm = ((m + 31)/32)*32;
        if( num_gpus > ceil((float)n/nb) ) {
            printf( " * too many GPUs for the matrix size, using %d GPUs\n", (int) num_gpus );
            *info = -1;
            return *info;
        }

        /* allocate workspace for each GPU */
        //lddat = ((((((n+nb-1)/nb)/num_gpus)*nb)+31)/32)*32;
        lddat = (n+nb-1)/nb;                 /* number of block columns         */
        lddat = (lddat+num_gpus-1)/num_gpus; /* number of block columns per GPU */
        lddat = nb*lddat;                    /* number of columns per GPU       */
        lddat = ((lddat+31)/32)*32;          /* make it a multiple of 32        */
        for(i=0; i<num_gpus; i++) {
            /* local-n and local-ld */
            n_local[i] = ((n/nb)/num_gpus)*nb;
            if (i < (n/nb)%num_gpus)
                n_local[i] += nb;
            else if (i == (n/nb)%num_gpus)
                n_local[i] += n%nb;

            /* workspaces */
            if (MAGMA_SUCCESS != magma_smalloc( &d_panel[i], 3*nb*maxm )) {
                for( j=0; j<i; j++ ) {
                    magma_free( d_panel[j] );
                    magma_free( d_lAT[j]   );
                }
                *info = MAGMA_ERR_DEVICE_ALLOC;
                return *info;
            }

            /* local-matrix storage */
            if (MAGMA_SUCCESS != magma_smalloc( &d_lAT[i], lddat*maxm )) {
                for( j=0; j<=i; j++ ) {
                    magma_free( d_panel[j] );
                }
                for( j=0; j<i; j++ ) {
                    magma_free( d_lAT[j] );
                }
                *info = MAGMA_ERR_DEVICE_ALLOC;
                return *info;
            }

            magma_stranspose2(d_lAT[i], 0, lddat, d_lA[i], 0, ldda, m, n_local[i], queues[2*i+1]);
        }
        for(i=0; i<num_gpus; i++) {
            magma_queue_sync(queues[2*i+1]);
        }

        /* cpu workspace */
        lddwork = maxm;
        if (MAGMA_SUCCESS != magma_smalloc_cpu( &work, lddwork*nb*num_gpus )) {
            for(i=0; i<num_gpus; i++ ) {
                magma_free( d_panel[i] );
                magma_free( d_lAT[i]   );
            }
            *info = MAGMA_ERR_HOST_ALLOC;
            return *info;
        }

        /* calling multi-gpu interface with allocated workspaces and streams */
        //magma_sgetrf1_mgpu( num_gpus, m, n, nb, 0, d_lAT, lddat, ipiv, d_panel, work, maxm,
        //                   (cudaStream_t **)streaml, info );
        magma_sgetrf2_mgpu(num_gpus, m, n, nb, 0, d_lAT, 0, lddat, ipiv, d_panel, 0, work, maxm,
                           info, queues);

        /* clean up */
        for( d=0; d<num_gpus; d++ ) {
            /* save on output */
            magma_stranspose2( d_lA[d], 0, ldda, d_lAT[d], 0, lddat, n_local[d], m, queues[2*d+1] );
            magma_queue_sync(queues[2*d+1]);
            magma_free( d_lAT[d]   );
            magma_free( d_panel[d] );
        } /* end of for d=1,..,num_gpus */
        magma_free_cpu( work );
    }

    return *info;
    /* End of MAGMA_SGETRF_MGPU */
}