MatSetOption MatSetOption Sets a parameter option for a matrix. Some options may be specific to certain storage formats. Sorted, row-oriented input will generally assemble the fastest. The default is row-oriented, nonsorted input.
Some options are relevant only for particular matrix types and are thus ignored by others.
Other options are not supported by certain matrix types and will generate an error message if set. Thus, if memory has not alredy been allocated for this particular data, then the insertion is ignored. For dense matrices, in which the entire array is allocated, no entries are ever ignored. This is a useful flag when debugging matrix memory preallocation. When this flag is set, the hash table is created during the first Matrix Assembly.