1SSYRK(1) BLAS routine SSYRK(1)
2
6 SSYRK - performs one of the symmetric rank k operations C :=
7 alpha*A*A' + beta*C,
8
10 SUBROUTINE SSYRK(UPLO,TRANS,N,K,ALPHA,A,LDA,BETA,C,LDC)
11 REAL ALPHA,BETA
13 INTEGER K,LDA,LDC,N
15 CHARACTER TRANS,UPLO
17 REAL A(LDA,*),C(LDC,*)
19
21 SSYRK performs one of the symmetric rank k operations
22 or
24 C := alpha*A'*A + beta*C,
26 where alpha and beta are scalars, C is an n by n symmetric matrix
28 and A is an n by k matrix in the first case and a k by n matrix
29 in the second case.
30
33 UPLO - CHARACTER*1.
34 On entry, UPLO specifies whether the upper or lower
35 triangular part of the array C is to be referenced as
36 follows:
37 UPLO = 'U' or 'u' Only the upper triangular part of C is to
39 be referenced.
40 UPLO = 'L' or 'l' Only the lower triangular part of C is to
42 be referenced.
43 Unchanged on exit.
45 TRANS - CHARACTER*1.
47 On entry, TRANS specifies the operation to be performed as
48 follows:
49 TRANS = 'N' or 'n' C := alpha*A*A' + beta*C.
51 TRANS = 'T' or 't' C := alpha*A'*A + beta*C.
53 TRANS = 'C' or 'c' C := alpha*A'*A + beta*C.
55 Unchanged on exit.
57 N - INTEGER.
59 On entry, N specifies the order of the matrix C. N must be at
60 least zero. Unchanged on exit.
61 K - INTEGER.
63 On entry with TRANS = 'N' or 'n', K specifies the number of
64 columns of the matrix A, and on entry with TRANS =
65 'T' or 't' or 'C' or 'c', K specifies the number of rows of
66 the matrix A. K must be at least zero. Unchanged on exit.
67 ALPHA - REAL .
69 On entry, ALPHA specifies the scalar alpha. Unchanged on exit.
70 A - REAL array of DIMENSION ( LDA, ka ), where ka is
72 k when TRANS = 'N' or 'n', and is n otherwise. Before
73 entry with TRANS = 'N' or 'n', the leading n by k part of
74 the array A must contain the matrix A, otherwise the leading
75 k by n part of the array A must contain the matrix A.
76 Unchanged on exit.
77 LDA - INTEGER.
79 On entry, LDA specifies the first dimension of A as declared in
80 the calling (sub) program. When TRANS = 'N' or 'n' then
81 LDA must be at least max( 1, n ), otherwise LDA must be at
82 least max( 1, k ). Unchanged on exit.
83 BETA - REAL .
85 On entry, BETA specifies the scalar beta. Unchanged on exit.
86 C - REAL array of DIMENSION ( LDC, n ).
88 Before entry with UPLO = 'U' or 'u', the leading n by n
89 upper triangular part of the array C must contain the upper tri‐
90 angular part of the symmetric matrix and the strictly lower
91 triangular part of C is not referenced. On exit, the upper tri‐
92 angular part of the array C is overwritten by the upper trian‐
93 gular part of the updated matrix. Before entry with UPLO =
94 'L' or 'l', the leading n by n lower triangular part of the
95 array C must contain the lower triangular part of the symmet‐
96 ric matrix and the strictly upper triangular part of C is not
97 referenced. On exit, the lower triangular part of the array C
98 is overwritten by the lower triangular part of the updated
99 matrix.
100 LDC - INTEGER.
102 On entry, LDC specifies the first dimension of C as declared in
103 the calling (sub) program. LDC must be at least max( 1,
104 n ). Unchanged on exit.
105
107 Level 3 Blas routine.
108 -- Written on 8-February-1989.
110 Jack Dongarra, Argonne National Laboratory.
111 Iain Duff, AERE Harwell.
112 Jeremy Du Croz, Numerical Algorithms Group Ltd.
113 Sven Hammarling, Numerical Algorithms Group Ltd.
114BLAS routine November 2008 SSYRK(1)