/** Purpose ------- CLATRD2 reduces NB rows and columns of a complex Hermitian matrix A to Hermitian tridiagonal form by an orthogonal similarity transformation Q' * A * Q, and returns the matrices V and W which are needed to apply the transformation to the unreduced part of A. If UPLO = MagmaUpper, CLATRD reduces the last NB rows and columns of a matrix, of which the upper triangle is supplied; if UPLO = MagmaLower, CLATRD reduces the first NB rows and columns of a matrix, of which the lower triangle is supplied. This is an auxiliary routine called by CHETRD2_GPU. It uses an accelerated HEMV that needs extra memory. Arguments --------- @param[in] uplo magma_uplo_t Specifies whether the upper or lower triangular part of the Hermitian matrix A is stored: - = MagmaUpper: Upper triangular - = MagmaLower: Lower triangular @param[in] n INTEGER The order of the matrix A. @param[in] nb INTEGER The number of rows and columns to be reduced. @param[in,out] A COMPLEX array, dimension (LDA,N) On entry, the Hermitian matrix A. If UPLO = MagmaUpper, the leading n-by-n upper triangular part of A contains the upper triangular part of the matrix A, and the strictly lower triangular part of A is not referenced. If UPLO = MagmaLower, the leading n-by-n lower triangular part of A contains the lower triangular part of the matrix A, and the strictly upper triangular part of A is not referenced. On exit: - if UPLO = MagmaUpper, the last NB columns have been reduced to tridiagonal form, with the diagonal elements overwriting the diagonal elements of A; the elements above the diagonal with the array TAU, represent the orthogonal matrix Q as a product of elementary reflectors; - if UPLO = MagmaLower, the first NB columns have been reduced to tridiagonal form, with the diagonal elements overwriting the diagonal elements of A; the elements below the diagonal with the array TAU, represent the orthogonal matrix Q as a product of elementary reflectors. See Further Details. @param[in] lda INTEGER The leading dimension of the array A. LDA >= (1,N). @param[out] e COMPLEX array, dimension (N-1) If UPLO = MagmaUpper, E(n-nb:n-1) contains the superdiagonal elements of the last NB columns of the reduced matrix; if UPLO = MagmaLower, E(1:nb) contains the subdiagonal elements of the first NB columns of the reduced matrix. @param[out] tau COMPLEX array, dimension (N-1) The scalar factors of the elementary reflectors, stored in TAU(n-nb:n-1) if UPLO = MagmaUpper, and in TAU(1:nb) if UPLO = MagmaLower. See Further Details. @param[out] W COMPLEX array, dimension (LDW,NB) The n-by-nb matrix W required to update the unreduced part of A. @param[in] ldw INTEGER The leading dimension of the array W. LDW >= max(1,N). Further Details --------------- If UPLO = MagmaUpper, the matrix Q is represented as a product of elementary reflectors Q = H(n) H(n-1) . . . H(n-nb+1). Each H(i) has the form H(i) = I - tau * v * v' where tau is a complex scalar, and v is a complex vector with v(i:n) = 0 and v(i-1) = 1; v(1:i-1) is stored on exit in A(1:i-1,i), and tau in TAU(i-1). If UPLO = MagmaLower, the matrix Q is represented as a product of elementary reflectors Q = H(1) H(2) . . . H(nb). Each H(i) has the form H(i) = I - tau * v * v' where tau is a complex scalar, and v is a complex vector with v(1:i) = 0 and v(i+1) = 1; v(i+1:n) is stored on exit in A(i+1:n,i), and tau in TAU(i). The elements of the vectors v together form the n-by-nb matrix V which is needed, with W, to apply the transformation to the unreduced part of the matrix, using a Hermitian rank-2k update of the form: A := A - V*W' - W*V'. The contents of A on exit are illustrated by the following examples with n = 5 and nb = 2: if UPLO = MagmaUpper: if UPLO = MagmaLower: ( a a a v4 v5 ) ( d ) ( a a v4 v5 ) ( 1 d ) ( a 1 v5 ) ( v1 1 a ) ( d 1 ) ( v1 v2 a a ) ( d ) ( v1 v2 a a a ) where d denotes a diagonal element of the reduced matrix, a denotes an element of the original matrix that is unchanged, and vi denotes an element of the vector defining H(i). @ingroup magma_cheev_aux ********************************************************************/ extern "C" magma_int_t magma_clatrd2(magma_uplo_t uplo, magma_int_t n, magma_int_t nb, magmaFloatComplex *A, magma_int_t lda, float *e, magmaFloatComplex *tau, magmaFloatComplex *W, magma_int_t ldw, magmaFloatComplex *dA, magma_int_t ldda, magmaFloatComplex *dW, magma_int_t lddw, magmaFloatComplex *dwork, magma_int_t ldwork) { #define A(i, j) (A + (j)*lda + (i)) #define W(i, j) (W + (j)*ldw + (i)) #define dA(i, j) (dA + (j)*ldda + (i)) #define dW(i, j) (dW + (j)*lddw + (i)) magma_int_t i; magmaFloatComplex c_neg_one = MAGMA_C_NEG_ONE; magmaFloatComplex c_one = MAGMA_C_ONE; magmaFloatComplex c_zero = MAGMA_C_ZERO; magmaFloatComplex value = MAGMA_C_ZERO; magma_int_t ione = 1; magma_int_t i_n, i_1, iw; magmaFloatComplex alpha; magmaFloatComplex *f; if (n <= 0) { return 0; } magma_queue_t stream; magma_queue_create( &stream ); magma_cmalloc_cpu( &f, n ); assert( f != NULL ); // TODO return error, or allocate outside clatrd if (uplo == MagmaUpper) { /* Reduce last NB columns of upper triangle */ for (i = n-1; i >= n - nb; --i) { i_1 = i + 1; i_n = n - i - 1; iw = i - n + nb; if (i < n-1) { /* Update A(1:i,i) */ #if defined(PRECISION_z) || defined(PRECISION_c) lapackf77_clacgv(&i_n, W(i, iw+1), &ldw); #endif blasf77_cgemv("No transpose", &i_1, &i_n, &c_neg_one, A(0, i+1), &lda, W(i, iw+1), &ldw, &c_one, A(0, i), &ione); #if defined(PRECISION_z) || defined(PRECISION_c) lapackf77_clacgv(&i_n, W(i, iw+1), &ldw); lapackf77_clacgv(&i_n, A(i, i+1), &ldw); #endif blasf77_cgemv("No transpose", &i_1, &i_n, &c_neg_one, W(0, iw+1), &ldw, A(i, i+1), &lda, &c_one, A(0, i), &ione); #if defined(PRECISION_z) || defined(PRECISION_c) lapackf77_clacgv(&i_n, A(i, i+1), &ldw); #endif } if (i > 0) { /* Generate elementary reflector H(i) to annihilate A(1:i-2,i) */ alpha = *A(i-1, i); lapackf77_clarfg(&i, &alpha, A(0, i), &ione, &tau[i - 1]); e[i-1] = MAGMA_C_REAL( alpha ); *A(i-1,i) = MAGMA_C_MAKE( 1, 0 ); /* Compute W(1:i-1,i) */ // 1. Send the block reflector A(0:n-i-1,i) to the GPU magma_csetvector( i, A(0, i), 1, dA(0, i), 1 ); //#if (GPUSHMEM < 200) //magma_chemv(MagmaUpper, i, c_one, dA(0, 0), ldda, // dA(0, i), ione, c_zero, dW(0, iw), ione); //#else magmablas_chemv_work(MagmaUpper, i, c_one, dA(0, 0), ldda, dA(0, i), ione, c_zero, dW(0, iw), ione, dwork, ldwork); //#endif // 2. Start putting the result back (asynchronously) magma_cgetmatrix_async( i, 1, dW(0, iw), lddw, W(0, iw) /*test*/, ldw, stream ); if (i < n-1) { blasf77_cgemv(MagmaConjTransStr, &i, &i_n, &c_one, W(0, iw+1), &ldw, A(0, i), &ione, &c_zero, W(i+1, iw), &ione); } // 3. Here is where we need it // TODO find the right place magma_queue_sync( stream ); if (i < n-1) { blasf77_cgemv("No transpose", &i, &i_n, &c_neg_one, A(0, i+1), &lda, W(i+1, iw), &ione, &c_one, W(0, iw), &ione); blasf77_cgemv(MagmaConjTransStr, &i, &i_n, &c_one, A(0, i+1), &lda, A(0, i), &ione, &c_zero, W(i+1, iw), &ione); blasf77_cgemv("No transpose", &i, &i_n, &c_neg_one, W(0, iw+1), &ldw, W(i+1, iw), &ione, &c_one, W(0, iw), &ione); } blasf77_cscal(&i, &tau[i - 1], W(0, iw), &ione); #if defined(PRECISION_z) || defined(PRECISION_c) cblas_cdotc_sub( i, W(0,iw), ione, A(0,i), ione, &value ); #else value = cblas_cdotc( i, W(0,iw), ione, A(0,i), ione ); #endif alpha = tau[i - 1] * -0.5f * value; blasf77_caxpy(&i, &alpha, A(0, i), &ione, W(0, iw), &ione); } } } else { /* Reduce first NB columns of lower triangle */ for (i = 0; i < nb; ++i) { /* Update A(i:n,i) */ i_n = n - i; #if defined(PRECISION_z) || defined(PRECISION_c) lapackf77_clacgv(&i, W(i, 0), &ldw); #endif blasf77_cgemv("No transpose", &i_n, &i, &c_neg_one, A(i, 0), &lda, W(i, 0), &ldw, &c_one, A(i, i), &ione); #if defined(PRECISION_z) || defined(PRECISION_c) lapackf77_clacgv(&i, W(i, 0), &ldw); lapackf77_clacgv(&i, A(i, 0), &lda); #endif blasf77_cgemv("No transpose", &i_n, &i, &c_neg_one, W(i, 0), &ldw, A(i, 0), &lda, &c_one, A(i, i), &ione); #if defined(PRECISION_z) || defined(PRECISION_c) lapackf77_clacgv(&i, A(i, 0), &lda); #endif if (i < n-1) { /* Generate elementary reflector H(i) to annihilate A(i+2:n,i) */ i_n = n - i - 1; alpha = *A(i+1, i); lapackf77_clarfg(&i_n, &alpha, A(min(i+2,n-1), i), &ione, &tau[i]); e[i] = MAGMA_C_REAL( alpha ); *A(i+1,i) = MAGMA_C_MAKE( 1, 0 ); /* Compute W(i+1:n,i) */ // 1. Send the block reflector A(i+1:n,i) to the GPU magma_csetvector( i_n, A(i+1, i), 1, dA(i+1, i), 1 ); //#if (GPUSHMEM < 200) //magma_chemv(MagmaLower, i_n, c_one, dA(i+1, i+1), ldda, dA(i+1, i), ione, c_zero, // dW(i+1, i), ione); //#else magmablas_chemv_work(MagmaLower, i_n, c_one, dA(i+1, i+1), ldda, dA(i+1, i), ione, c_zero, dW(i+1, i), ione, dwork, ldwork); //#endif // 2. Start putting the result back (asynchronously) magma_cgetmatrix_async( i_n, 1, dW(i+1, i), lddw, W(i+1, i), ldw, stream ); blasf77_cgemv(MagmaConjTransStr, &i_n, &i, &c_one, W(i+1, 0), &ldw, A(i+1, i), &ione, &c_zero, W(0, i), &ione); blasf77_cgemv("No transpose", &i_n, &i, &c_neg_one, A(i+1, 0), &lda, W(0, i), &ione, &c_zero, f, &ione); blasf77_cgemv(MagmaConjTransStr, &i_n, &i, &c_one, A(i+1, 0), &lda, A(i+1, i), &ione, &c_zero, W(0, i), &ione); // 3. Here is where we need it magma_queue_sync( stream ); if (i != 0) blasf77_caxpy(&i_n, &c_one, f, &ione, W(i+1, i), &ione); blasf77_cgemv("No transpose", &i_n, &i, &c_neg_one, W(i+1, 0), &ldw, W(0, i), &ione, &c_one, W(i+1, i), &ione); blasf77_cscal(&i_n, &tau[i], W(i+1,i), &ione); #if defined(PRECISION_z) || defined(PRECISION_c) cblas_cdotc_sub( i_n, W(i+1,i), ione, A(i+1,i), ione, &value ); #else value = cblas_cdotc( i_n, W(i+1,i), ione, A(i+1,i), ione ); #endif alpha = tau[i] * -0.5f * value; blasf77_caxpy(&i_n, &alpha, A(i+1, i), &ione, W(i+1,i), &ione); } } } magma_free_cpu(f); magma_queue_destroy( stream ); return 0; } /* magma_clatrd */
/** Purpose ------- CLATRD2 reduces NB rows and columns of a complex Hermitian matrix A to Hermitian tridiagonal form by an orthogonal similarity transformation Q' * A * Q, and returns the matrices V and W which are needed to apply the transformation to the unreduced part of A. If UPLO = MagmaUpper, CLATRD reduces the last NB rows and columns of a matrix, of which the upper triangle is supplied; if UPLO = MagmaLower, CLATRD reduces the first NB rows and columns of a matrix, of which the lower triangle is supplied. This is an auxiliary routine called by CHETRD2_GPU. It uses an accelerated HEMV that needs extra memory. Arguments --------- @param[in] uplo magma_uplo_t Specifies whether the upper or lower triangular part of the Hermitian matrix A is stored: - = MagmaUpper: Upper triangular - = MagmaLower: Lower triangular @param[in] n INTEGER The order of the matrix A. @param[in] nb INTEGER The number of rows and columns to be reduced. @param[in,out] A COMPLEX array, dimension (LDA,N) On entry, the Hermitian matrix A. If UPLO = MagmaUpper, the leading n-by-n upper triangular part of A contains the upper triangular part of the matrix A, and the strictly lower triangular part of A is not referenced. If UPLO = MagmaLower, the leading n-by-n lower triangular part of A contains the lower triangular part of the matrix A, and the strictly upper triangular part of A is not referenced. On exit: - if UPLO = MagmaUpper, the last NB columns have been reduced to tridiagonal form, with the diagonal elements overwriting the diagonal elements of A; the elements above the diagonal with the array TAU, represent the orthogonal matrix Q as a product of elementary reflectors; - if UPLO = MagmaLower, the first NB columns have been reduced to tridiagonal form, with the diagonal elements overwriting the diagonal elements of A; the elements below the diagonal with the array TAU, represent the orthogonal matrix Q as a product of elementary reflectors. See Further Details. @param[in] lda INTEGER The leading dimension of the array A. LDA >= (1,N). @param[out] e COMPLEX array, dimension (N-1) If UPLO = MagmaUpper, E(n-nb:n-1) contains the superdiagonal elements of the last NB columns of the reduced matrix; if UPLO = MagmaLower, E(1:nb) contains the subdiagonal elements of the first NB columns of the reduced matrix. @param[out] tau COMPLEX array, dimension (N-1) The scalar factors of the elementary reflectors, stored in TAU(n-nb:n-1) if UPLO = MagmaUpper, and in TAU(1:nb) if UPLO = MagmaLower. See Further Details. @param[out] W COMPLEX array, dimension (LDW,NB) The n-by-nb matrix W required to update the unreduced part of A. @param[in] ldw INTEGER The leading dimension of the array W. LDW >= max(1,N). @param dA TODO: dimension (ldda, n) ?? @param ldda TODO: ldda >= n ?? @param dW TODO: dimension (lddw, 2*nb) ?? @param lddw TODO: lddw >= n ?? @param dwork TODO: dimension (ldwork) ?? @param ldwork TODO: ldwork >= ceil(n/64)*ldda ?? @param[in] queue magma_queue_t Queue to execute in. Further Details --------------- If UPLO = MagmaUpper, the matrix Q is represented as a product of elementary reflectors Q = H(n) H(n-1) . . . H(n-nb+1). Each H(i) has the form H(i) = I - tau * v * v' where tau is a complex scalar, and v is a complex vector with v(i:n) = 0 and v(i-1) = 1; v(1:i-1) is stored on exit in A(1:i-1,i), and tau in TAU(i-1). If UPLO = MagmaLower, the matrix Q is represented as a product of elementary reflectors Q = H(1) H(2) . . . H(nb). Each H(i) has the form H(i) = I - tau * v * v' where tau is a complex scalar, and v is a complex vector with v(1:i) = 0 and v(i+1) = 1; v(i+1:n) is stored on exit in A(i+1:n,i), and tau in TAU(i). The elements of the vectors v together form the n-by-nb matrix V which is needed, with W, to apply the transformation to the unreduced part of the matrix, using a Hermitian rank-2k update of the form: A := A - V*W' - W*V'. The contents of A on exit are illustrated by the following examples with n = 5 and nb = 2: if UPLO = MagmaUpper: if UPLO = MagmaLower: ( a a a v4 v5 ) ( d ) ( a a v4 v5 ) ( 1 d ) ( a 1 v5 ) ( v1 1 a ) ( d 1 ) ( v1 v2 a a ) ( d ) ( v1 v2 a a a ) where d denotes a diagonal element of the reduced matrix, a denotes an element of the original matrix that is unchanged, and vi denotes an element of the vector defining H(i). @ingroup magma_cheev_aux ********************************************************************/ extern "C" magma_int_t magma_clatrd2( magma_uplo_t uplo, magma_int_t n, magma_int_t nb, magmaFloatComplex *A, magma_int_t lda, float *e, magmaFloatComplex *tau, magmaFloatComplex *W, magma_int_t ldw, magmaFloatComplex *work, magma_int_t lwork, magmaFloatComplex_ptr dA, magma_int_t ldda, magmaFloatComplex_ptr dW, magma_int_t lddw, magmaFloatComplex_ptr dwork, magma_int_t ldwork, magma_queue_t queue ) { #define A(i_, j_) (A + (i_) + (j_)*lda) #define W(i_, j_) (W + (i_) + (j_)*ldw) #define dA(i_, j_) (dA + (i_) + (j_)*ldda) #define dW(i_, j_) (dW + (i_) + (j_)*lddw) /* Constants */ const magmaFloatComplex c_neg_one = MAGMA_C_NEG_ONE; const magmaFloatComplex c_one = MAGMA_C_ONE; const magmaFloatComplex c_zero = MAGMA_C_ZERO; const magma_int_t ione = 1; /* Local variables */ magmaFloatComplex alpha, value; magma_int_t i, i_n, i_1, iw; /* Check arguments */ magma_int_t info = 0; if ( uplo != MagmaLower && uplo != MagmaUpper ) { info = -1; } else if ( n < 0 ) { info = -2; } else if ( nb < 1 ) { info = -3; } else if ( lda < max(1,n) ) { info = -5; } else if ( ldw < max(1,n) ) { info = -9; } else if ( lwork < max(1,n) ) { info = -11; } else if ( ldda < max(1,n) ) { info = -13; } else if ( lddw < max(1,n) ) { info = -15; } else if ( ldwork < ldda*magma_ceildiv(n,64) ) { info = -17; } if (info != 0) { magma_xerbla( __func__, -(info) ); return info; } /* Quick return if possible */ if (n == 0) { return info; } if (uplo == MagmaUpper) { /* Reduce last NB columns of upper triangle */ for (i = n-1; i >= n - nb; --i) { i_1 = i + 1; i_n = n - i - 1; iw = i - n + nb; if (i < n-1) { /* Update A(1:i,i) */ #ifdef COMPLEX lapackf77_clacgv( &i_n, W(i, iw+1), &ldw ); #endif blasf77_cgemv( "No transpose", &i_1, &i_n, &c_neg_one, A(0, i+1), &lda, W(i, iw+1), &ldw, &c_one, A(0, i), &ione ); #ifdef COMPLEX lapackf77_clacgv( &i_n, W(i, iw+1), &ldw ); lapackf77_clacgv( &i_n, A(i, i+1), &lda ); #endif blasf77_cgemv( "No transpose", &i_1, &i_n, &c_neg_one, W(0, iw+1), &ldw, A(i, i+1), &lda, &c_one, A(0, i), &ione ); #ifdef COMPLEX lapackf77_clacgv( &i_n, A(i, i+1), &lda ); #endif } if (i > 0) { /* Generate elementary reflector H(i) to annihilate A(1:i-2,i) */ alpha = *A(i-1, i); lapackf77_clarfg( &i, &alpha, A(0, i), &ione, &tau[i - 1] ); e[i-1] = MAGMA_C_REAL( alpha ); *A(i-1,i) = MAGMA_C_ONE; /* Compute W(1:i-1,i) */ // 1. Send the block reflector A(0:n-i-1,i) to the GPU magma_csetvector_async( i, A(0, i), 1, dA(0, i), 1, queue ); magmablas_chemv_work( MagmaUpper, i, c_one, dA(0, 0), ldda, dA(0, i), ione, c_zero, dW(0, iw), ione, dwork, ldwork, queue ); // 2. Start getting the result back (asynchronously) magma_cgetmatrix_async( i, 1, dW(0, iw), lddw, W(0, iw), ldw, queue ); if (i < n-1) { blasf77_cgemv( MagmaConjTransStr, &i, &i_n, &c_one, W(0, iw+1), &ldw, A(0, i), &ione, &c_zero, W(i+1, iw), &ione ); } // 3. Here we need chemv result W(0, iw) magma_queue_sync( queue ); if (i < n-1) { blasf77_cgemv( "No transpose", &i, &i_n, &c_neg_one, A(0, i+1), &lda, W(i+1, iw), &ione, &c_one, W(0, iw), &ione ); blasf77_cgemv( MagmaConjTransStr, &i, &i_n, &c_one, A(0, i+1), &lda, A(0, i), &ione, &c_zero, W(i+1, iw), &ione ); blasf77_cgemv( "No transpose", &i, &i_n, &c_neg_one, W(0, iw+1), &ldw, W(i+1, iw), &ione, &c_one, W(0, iw), &ione ); } blasf77_cscal( &i, &tau[i - 1], W(0, iw), &ione ); value = magma_cblas_cdotc( i, W(0,iw), ione, A(0,i), ione ); alpha = tau[i - 1] * -0.5f * value; blasf77_caxpy( &i, &alpha, A(0, i), &ione, W(0, iw), &ione ); } } } else { /* Reduce first NB columns of lower triangle */ for (i = 0; i < nb; ++i) { /* Update A(i:n,i) */ i_n = n - i; #ifdef COMPLEX lapackf77_clacgv( &i, W(i, 0), &ldw ); #endif blasf77_cgemv( "No transpose", &i_n, &i, &c_neg_one, A(i, 0), &lda, W(i, 0), &ldw, &c_one, A(i, i), &ione ); #ifdef COMPLEX lapackf77_clacgv( &i, W(i, 0), &ldw ); lapackf77_clacgv( &i, A(i, 0), &lda ); #endif blasf77_cgemv( "No transpose", &i_n, &i, &c_neg_one, W(i, 0), &ldw, A(i, 0), &lda, &c_one, A(i, i), &ione ); #ifdef COMPLEX lapackf77_clacgv( &i, A(i, 0), &lda ); #endif if (i < n-1) { /* Generate elementary reflector H(i) to annihilate A(i+2:n,i) */ i_n = n - i - 1; alpha = *A(i+1, i); lapackf77_clarfg( &i_n, &alpha, A(min(i+2,n-1), i), &ione, &tau[i] ); e[i] = MAGMA_C_REAL( alpha ); *A(i+1,i) = MAGMA_C_ONE; /* Compute W(i+1:n,i) */ // 1. Send the block reflector A(i+1:n,i) to the GPU magma_csetvector_async( i_n, A(i+1, i), 1, dA(i+1, i), 1, queue ); magmablas_chemv_work( MagmaLower, i_n, c_one, dA(i+1, i+1), ldda, dA(i+1, i), ione, c_zero, dW(i+1, i), ione, dwork, ldwork, queue ); // 2. Start getting the result back (asynchronously) magma_cgetmatrix_async( i_n, 1, dW(i+1, i), lddw, W(i+1, i), ldw, queue ); blasf77_cgemv( MagmaConjTransStr, &i_n, &i, &c_one, W(i+1, 0), &ldw, A(i+1, i), &ione, &c_zero, W(0, i), &ione ); blasf77_cgemv( "No transpose", &i_n, &i, &c_neg_one, A(i+1, 0), &lda, W(0, i), &ione, &c_zero, work, &ione ); blasf77_cgemv( MagmaConjTransStr, &i_n, &i, &c_one, A(i+1, 0), &lda, A(i+1, i), &ione, &c_zero, W(0, i), &ione ); // 3. Here we need chemv result W(i+1, i) magma_queue_sync( queue ); if (i != 0) blasf77_caxpy( &i_n, &c_one, work, &ione, W(i+1, i), &ione ); blasf77_cgemv( "No transpose", &i_n, &i, &c_neg_one, W(i+1, 0), &ldw, W(0, i), &ione, &c_one, W(i+1, i), &ione ); blasf77_cscal( &i_n, &tau[i], W(i+1,i), &ione ); value = magma_cblas_cdotc( i_n, W(i+1,i), ione, A(i+1,i), ione ); alpha = tau[i] * -0.5f * value; blasf77_caxpy( &i_n, &alpha, A(i+1, i), &ione, W(i+1,i), &ione ); } } } return info; } /* magma_clatrd */