# sparse_insert_block_double(_:_:_:_:_:_:) Inserts a dense block of entries into a double-precision matrix. ``` func sparse_insert_block_double(_ A: sparse_matrix_double!, _ val: UnsafePointer!, _ row_stride: sparse_dimension, _ col_stride: sparse_dimension, _ bi: sparse_index, _ bj: sparse_index) -> sparse_status ``` ## Parameters `A` The sparse matrix, *A*,_ _which must have been created with [`sparse_matrix_block_create_double(_:_:_:_:)`](/documentation/Accelerate/sparse_matrix_block_create_double(_:_:_:_:)) or [`sparse_matrix_variable_block_create_double(_:_:_:_:)`](/documentation/Accelerate/sparse_matrix_variable_block_create_double(_:_:_:_:)). [`SPARSE_ILLEGAL_PARAMETER`](/documentation/Accelerate/SPARSE_ILLEGAL_PARAMETER) is returned if not met. `A` holds block dimensions (fixed or variable) set with matrix object creation routine. `val` Pointer to block to be inserted at block index location `A[bi,bj]`. The block is of dimension `k * l` where `k` and `l` are set for `bi,bj` at object creation time. The strides between elements for rows and columns are provided in `row_stride` and `col_stride`. `row_stride` The row stride in number of elements to move from one row to the next for the block `val`. `col_stride` The column stride in number of elements to move from one column to the next for the block `val`. `bi` The block row index where `val` is to be inserted. Indexing is zero based, the first block is located at `0,0`. Index is assumed to be within the bounds of the matrix object, undefined behavior if not met. `bj` The block column index where `val` is to be inserted. Indexing is zero based, the first block is located at `0,0`. Index is assumed to be within the bounds of the matrix object, undefined behavior if not met. ## Return Value On successful insertion, `A` has been updated with the value and [`SPARSE_SUCCESS`](/documentation/Accelerate/SPARSE_SUCCESS) is returned. If `A` creation requirements are not met, [`SPARSE_ILLEGAL_PARAMETER`](/documentation/Accelerate/SPARSE_ILLEGAL_PARAMETER) is returned and `A` is unchanged. ## Discussion Use to build a sparse matrix by providing a dense block for entry at block location `A[bi,bj]`. Block size is determined at object creation time. Given a block dimension of `k * l` and for location `bi,bj`, update as: `A[bi,bj][i,j] = val[i*row_stride + j*col_stride]` for each `i` in `k` and each `j` in `l`. Note that matrix properties cannot be modified after value insertion begins.This includes properties such as specifying a triangular matrix.Insertion can be expensive, generally speaking it is best to do a batch update. Inserted values may be temporarily held internally within the object and only inserted into the sparse format when a later computation triggers a need to insert. > Important: > Apple provides the BLAS and LAPACK libraries under the Accelerate framework to be in line with LAPACK 3.9.1. Starting with iOS 26, iPadOS 26, macOS 26, tvOS 26, visionOS 26, and watchOS 26, the libraries are in line with LAPACK 3.12.0. These new interfaces provide additional functionality, as well as a new ILP64 interface. To use the new interfaces, define `ACCELERATE_NEW_LAPACK` before including the Accelerate or vecLib headers. For ILP64 interfaces, also define `ACCELERATE_LAPACK_ILP64`. For Swift projects, specify `ACCELERATE_NEW_LAPACK=1` and `ACCELERATE_LAPACK_ILP64=1` as preprocessor macros in Xcode build settings under Apple Clang - Preprocessing > Preprocessor Macros. --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)