SSYMM/DSYMM/CHEMM/CSYMM/ZHEMM/ZSYMM

Matrix-matrix multiply

If an error in the arguments is detected, the subprograms call error handler XERBLA, which writes an error message onto the standard error file and terminates execution. The standard version of XERBLA (refer to the end of this chapter) can be replaced with a user-supplied version to change the error procedure. Error conditions are

side ≠ ’L’ or ’l’ or ’R’ or ’r’ uplo ≠ ’L’ or ’l’ or ’U’ or ’u’ m < 0

n < 0

lda too small ldb < max(m,1) ldc < max(m,1)

Actual character arguments in a subroutine call can be longer than the corresponding dummy arguments. Therefore, readability of the CALL statement may be improved, for example, by coding the side argument as ’LEFT’ for ’L’ or ’RIGHT’ for ’R’. Refer to “Example 2.”

Example 1 Form the REAL*4 matrix product C = AB, where A is a 6-by-6 real symmetric real matrix whose upper triangle is stored in the upper triangle of an array A of dimension 10-by-10, B is a 6-by-8 real matrix stored in an array B of dimension 10-by-10, and C is a 6-by-8 real matrix stored in an array C, also of dimension 10-by-10.

CHARACTER*1 SIDE,UPLO

 

INTEGER*4

M,N,LDA,LDB,LDC

 

REAL*4

ALPHA,BETA,A(10,10),B(10,10),C(10,10)

SIDE = ’L’

 

 

UPLO = ’U’

 

 

M = 6

 

 

N = 8

 

 

ALPHA = 1.0

 

 

BETA = 0.0

 

 

LDA = 10

 

 

LDB = 10

 

 

LDC = 10

 

 

CALL SSYMM (SIDE,UPLO,M,N,ALPHA,A,LDA,B,LDB,BETA,C,LDC)

Example 2 Form the COMPLEX*8 matrix-matrix product C =

1

--BA – ρC , where ρ is a

 

 

2

scalar, A is an 8-by-8 complex Hermitian matrix whose lower triangle is stored in the lower triangle of an array A of dimension 10-by-10, B is a 6-by-8 complex matrix stored in an array whose dimensions are 10-by-10, and C is a 6-by-8 complex matrix stored in an array C, also of dimension 10-by-10.

268HP MLIB User’s Guide