---
name: "dgemmtr.f"
section: "3"
platform: "linux"
package: "lapack-doc"
version: "3.12.1-2"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/dgemmtr.f"
---

# dgemmtr.f(3)

## NAME

BLAS/SRC/dgemmtr.f

## SYNOPSIS

### Functions/Subroutines

subroutine **dgemmtr** (uplo, transa, transb, n, k, alpha, a, lda, b, ldb, beta, c, ldc)\
 **DGEMMTR**

## Function/Subroutine Documentation

### subroutine dgemmtr (character uplo, character transa, character transb, integer n, integer k, double precision alpha, double precision, dimension(lda,\*) a, integer lda, double precision, dimension(ldb,\*) b, integer ldb, double precision beta, double precision, dimension(ldc,\*) c, integer ldc)

**DGEMMTR**

**Purpose:**

```
!>
!> DGEMMTR  performs one of the matrix-matrix operations
!>
!>    C := alpha*op( A )*op( B ) + beta*C,
!>
!> where  op( X ) is one of
!>
!>    op( X ) = X   or   op( X ) = X**T,
!>
!> alpha and beta are scalars, and A, B and C are matrices, with op( A )
!> an n by k matrix,  op( B )  a  k by n matrix and  C an n by n matrix.
!> Thereby, the routine only accesses and updates the upper or lower
!> triangular part of the result matrix C. This behaviour can be used if
!> the resulting matrix C is known to be symmetric.
!>
```

**Parameters**

*UPLO*

```
!>          UPLO is CHARACTER*1
!>           On entry, UPLO specifies whether the lower or the upper
!>           triangular part of C is access and updated.
!>
!>              UPLO = 'L' or 'l', the lower triangular part of C is used.
!>
!>              UPLO = 'U' or 'u', the upper triangular part of C is used.
!>
```

*TRANSA*

```
!>          TRANSA is CHARACTER*1
!>           On entry, 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*

```
!>          TRANSB is CHARACTER*1
!>           On entry, TRANSB specifies the form of op( B ) to be used in
!>           the matrix multiplication as follows:
!>
!>              TRANSB = 'N' or 'n',  op( B ) = B.
!>
!>              TRANSB = 'T' or 't',  op( B ) = B**T.
!>
!>              TRANSB = 'C' or 'c',  op( B ) = B**T.
!>
```

*N*

```
!>          N is INTEGER
!>           On entry,  N specifies the number of rows and columns of
!>           the matrix C, the number of columns of op(B) and the number
!>           of rows of op(A).  N must be at least zero.
!>
```

*K*

```
!>          K is INTEGER
!>           On entry,  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*

```
!>          ALPHA is DOUBLE PRECISION.
!>           On entry, ALPHA specifies the scalar alpha.
!>
```

*A*

```
!>          A is DOUBLE PRECISION array, dimension ( LDA, ka ), where ka is
!>           k  when  TRANSA = 'N' or 'n',  and is  n  otherwise.
!>           Before entry with  TRANSA = 'N' or 'n',  the leading  n 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*

```
!>          LDA is INTEGER
!>           On entry, LDA specifies the first dimension of A as declared
!>           in the calling (sub) program. When  TRANSA = 'N' or 'n' then
!>           LDA must be at least  max( 1, n ), otherwise  LDA must be at
!>           least  max( 1, k ).
!>
```

*B*

```
!>          B is DOUBLE PRECISION array, 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*

```
!>          LDB is INTEGER
!>           On entry, LDB specifies the first dimension of B as declared
!>           in the calling (sub) program. When  TRANSB = 'N' or 'n' then
!>           LDB must be at least  max( 1, k ), otherwise  LDB must be at
!>           least  max( 1, n ).
!>
```

*BETA*

```
!>          BETA is DOUBLE PRECISION.
!>           On entry,  BETA  specifies the scalar  beta.  When  BETA  is
!>           supplied as zero then C need not be set on input.
!>
```

*C*

```
!>          C is DOUBLE PRECISION array, dimension ( LDC, N )
!>           Before entry, the leading  n 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 upper or lower triangular part of the matrix
!>           C  is overwritten by the n by n matrix
!>           ( alpha*op( A )*op( B ) + beta*C ).
!>
```

*LDC*

```
!>          LDC is INTEGER
!>           On entry, LDC specifies the first dimension of C as declared
!>           in  the  calling  (sub)  program.   LDC  must  be  at  least
!>           max( 1, n ).
!>
```

**Author**

Martin Koehler

**Further Details:**

```
!>
!>  Level 3 Blas routine.
!>
!>  -- Written on 19-July-2023.
!>     Martin Koehler, MPI Magdeburg
!>
```

Definition at line **189** of file **dgemmtr.f**.

## Author

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