# PetscBT#

PETSc bitarrays, efficient storage of arrays of boolean values

## Synopsis#

typedef char *PetscBT;


## Notes#

The following routines do not have their own manual pages

     PetscBTCreate(m,&bt)         - creates a bit array with enough room to hold m values
PetscBTDestroy(&bt)          - destroys the bit array
PetscBTMemzero(m,bt)         - zeros the entire bit array (sets all values to false)
PetscBTSet(bt,index)         - sets a particular entry as true
PetscBTClear(bt,index)       - sets a particular entry as false
PetscBTLookup(bt,index)      - returns the value
PetscBTLookupSet(bt,index)   - returns the value and then sets it true
PetscBTLookupClear(bt,index) - returns the value and then sets it false
PetscBTLength(m)             - returns number of bytes in array with m bits
PetscBTView(m,bt,viewer)     - prints all the entries in a bit array


PETSc does not check error flags on PetscBTLookup(), PetcBTLookupSet(), PetscBTLength() because error checking would cost hundreds more cycles then the operation.