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Matrix Multiply

Source: R/wrappers.R
dgemm.Rd

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[,]
#>      alpha beta gamma
#> [1,]  -3.5 -3.5  -3.5
#> [2,]  -3.5 -3.5  -3.5
#> [3,]  -3.5 -3.5  -3.5
E = dgemm(ALPHA=2.0, A=A, B=B, BETA=0.5, C=C)
E[,] # Same result
#>      alpha beta gamma
#> [1,]  -3.5 -3.5  -3.5
#> [2,]  -3.5 -3.5  -3.5
#> [3,]  -3.5 -3.5  -3.5

# The big.matrix file backings will be deleted when garbage collected.
rm(A,B,C,E)
gc()
#>           used (Mb) gc trigger  (Mb) limit (Mb) max used  (Mb)
#> Ncells 1144378 61.2    2286118 122.1         NA  2286118 122.1
#> Vcells 2048949 15.7    8388608  64.0      65536  5285191  40.4