dgemm: Matrix Multiply

In bigalgebra: 'BLAS' and 'LAPACK' Routines for Native R Matrices and 'big.matrix' Objects

Matrix Multiply

Description

This is function provides dgemm functionality, which DGEMM performs one of the matrix-matrix operations. C := ALPHA * op(A) * op(B) + BETA * C.

Usage

dgemm(
  TRANSA = "N",
  TRANSB = "N",
  M = NULL,
  N = NULL,
  K = NULL,
  ALPHA = 1,
  A,
  LDA = NULL,
  B,
  LDB = NULL,
  BETA = 0,
  C,
  LDC = NULL,
  COFF = 0
)

Arguments

TRANSA	a character. TRANSA specifies the form of op( A ) to be used in the matrix multiplication as follows: TRANSA = 'N' or 'n', op( A ) = A. TRANSA = 'T' or 't', op( A ) = A**T. TRANSA = 'C' or 'c', op( A ) = A**T.
TRANSB	a character. TRANSB specifies the form of op( B ) to be used in the matrix multiplication as follows: #' TRANSA = 'N' or 'n', op( B ) = B. TRANSA = 'T' or 't', op( B ) = B**T. TRANSA = 'C' or 'c', op( B ) = B**T.
M	an integer. M specifies the number of rows of the matrix op( A ) and of the matrix C. M must be at least zero.
N	an integer. N specifies the number of columns of the matrix op( B ) and of the matrix C. N must be at least zero.
K	an integer. K specifies the number of columns of the matrix op( A ) and the number of rows of the matrix op( B ). K must be at least zero.
ALPHA	a real number. Specifies the scalar alpha.
A	a matrix of dimension (LDA, ka), where ka is k when TRANSA = 'N' or 'n', and is m otherwise. Before entry with TRANSA = 'N' or 'n', the leading m by k part of the array A must contain the matrix A, otherwise the leading k by m part of the array A must contain the matrix A.
LDA	an integer.
B	a matrix of dimension ( LDB, kb ), where kb is n when TRANSB = 'N' or 'n', and is k otherwise. Before entry with TRANSB = 'N' or 'n', the leading k by n part of the array B must contain the matrix B, otherwise the leading n by k part of the array B must contain the matrix B.
LDB	an integer.
BETA	a real number. Specifies the scalar beta
C	a matrix of dimension ( LDC, N ). Before entry, the leading m by n part of the array C must contain the matrix C, except when beta is zero, in which case C need not be set on entry. On exit, the array C is overwritten by the m by n matrix ( alpha*op( A )*op( B ) + beta*C ).
LDC	an integer.
COFF	offset for C.

Value

Update C with the result.

Examples

require(bigmemory)
A = as.big.matrix(matrix(1, nrow=3, ncol=2))
B <- big.matrix(2, 3, type="double", init=-1,
                dimnames=list(NULL, c("alpha", "beta")), shared=FALSE)
C = big.matrix(3, 3, type="double", init=1,
               dimnames=list(NULL, c("alpha", "beta", "gamma")), shared=FALSE)  
2*A[,]%*%B[,]+0.5*C[,]
E = dgemm(ALPHA=2.0, A=A, B=B, BETA=0.5, C=C)
E[,] # Same result

# The big.matrix file backings will be deleted when garbage collected.
rm(A,B,C,E)
gc()

bigalgebra documentation built on Sept. 30, 2024, 9:42 a.m.