cuSPARSE dense times sparse

2
votes

I need to calculate the following matrix math:
D * A
Where D is dense, and A is sparse, in CSC format.
cuSPARSE allows multiplying sparse * dense, where sparse matrix is in CSR format.

Following a related question, I can "convert" CSC to CSR simply by transposing A.
Also I can calculate (A^T * D^T)^T, as I can handle getting the result transposed.
In this method I can also avoid "transposing" A, because CSR^T is CSC.

The only problem is that cuSPARSE doesn't support transposing D in this operation, so I have to tranpose it beforehand, or convert it to CSR, which is a total waste, as it is very dense.

Is there any workaround?
Thanks.

1
cudasparse-matrix
Probably you know this already, but you can transpose a dense matrix in cublas using the geam function. – Robert Crovella
Is this a stand alone operation or are you doing something on the lines of A' * D * A ? – Pavan Yalamanchili
The operation is X - D * A where X & D are very dense and A is very sparse – MrDor

1 Answers

1
votes

I found a workaround.
I changed the memory accesses to D in my entire code.
If D is an mxn matrix, and I used to access it by D[j * m + i], now I'm accessing it by D[i * n + j], meaning I made it rows-major instead of columns-major.
cuSPARSE expectes matrices in column-major format, and because rows-major transposed is columns-major, I can pass D to cuSPARSE functions as a fake transpose without the need to make the transpose.