dgemm {bigalgebra} R Documentation

## 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()


[Package bigalgebra version 1.1.1 Index]