如何在Excel VBA中调用Rblas.dll的dgemm函数及结果异常问题

核心错误点 #

• 整数类型不匹配：VBA的Integer是16位整数，而BLAS接口要求的是32位整数，对应VBA的Long类型，所有整形参数传递错误导致dgemm执行逻辑异常。
• 隐式Variant类型：VBA中逗号分隔声明变量时，只有最后一个变量会被指定为标注的类型，其余默认是Variant，alpha、m等变量实际类型与BLAS要求的Double/32位整数不匹配。
• 矩阵存储顺序适配：BLAS基于Fortran编写，采用列优先存储，VBA二维数组同样是列优先存储，若按日常行优先逻辑赋值矩阵，需要调整transa/transb参数为转置状态，否则计算的是原矩阵转置后的乘积。

修改后的完整代码 #

Declare PtrSafe Sub dgemm_ Lib "C:\Program Files\R\R-4.0.2\bin\x64\Rblas.dll" _
(ByVal transa As String, _
ByVal transb As String, _
ByRef m As Long, _
ByRef n As Long, _
ByRef k As Long, _
ByRef alpha As Double, _
ByRef a As Double, _
ByRef lda As Long, _
ByRef b As Double, _
ByRef ldb As Long, _
ByRef beta As Double, _
ByRef c As Double, _
ByRef ldc As Long)

Sub test_dgemm()
    Dim alpha As Double, beta As Double
    Dim a(0 To 1, 0 To 1) As Double, b(0 To 1, 0 To 1) As Double, c(0 To 1, 0 To 1) As Double
    Dim m As Long, n As Long, k As Long, lda As Long, ldb As Long, ldc As Long
    Dim transa As String, transb As String

    a(0, 0) = 1
    a(0, 1) = 2
    a(1, 0) = 3
    a(1, 1) = 4

    b(0, 0) = 1
    b(0, 1) = 2
    b(1, 0) = 3
    b(1, 1) = 4

    c(0, 0) = 1
    c(0, 1) = 2
    c(1, 0) = 3
    c(1, 1) = 4

    m = 2
    n = 2
    k = 2
    lda = 2
    ldb = 2
    ldc = 2
    alpha = 1
    beta = 0
    ' 若要按行优先逻辑计算原矩阵乘积，将transa、transb设为"T"即可
    transa = "N"
    transb = "N"
    Call dgemm_(transa, transb, m, n, k, alpha, a(0, 0), lda, b(0, 0), ldb, beta, c(0, 0), ldc)
End Sub

补充说明 #

修改后运行代码，若保留transa="N"、transb="N"，得到的是列优先存储下的矩阵乘积结果，若要得到你预期的13 16 29 36，调整矩阵赋值内容或者trans参数即可。

内容的提问来源于stack exchange，提问作者Actuary David