code: public static int cusparseCsrmvEx_bufferSize(
          cusparseHandle handle, 
          int alg, 
          int transA, 
          int m, 
          int n, 
          int nnz, 
          Pointer alpha, 
          int alphatype, 
          cusparseMatDescr descrA, 
          Pointer csrValA, 
          int csrValAtype, 
          Pointer csrRowPtrA, 
          Pointer csrColIndA, 
          Pointer x, 
          int xtype, 
          Pointer beta, 
          int betatype, 
          Pointer y, 
          int ytype, 
          int executiontype, 
          long[] bufferSizeInBytes)
      {
          return checkResult(cusparseCsrmvEx_bufferSizeNative(handle, alg, transA, m, n, nnz, alpha, alphatype, descrA, csrValA, csrValAtype, csrRowPtrA, csrColIndA, x, xtype, beta, betatype, y, ytype, executiontype, bufferSizeInBytes));
      }
docs: Returns number of bytes