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NAME

       srf_index_hash - Adds a hash-table index to an SRF file.

SYNOPSIS

       srf_index_hash  [-c] srf_archive

DESCRIPTION

       srf_index_hash  adds  and  index to an SRF file or replaces an existing
       index with a new one. In the case of concatenated SRF  files  only  the
       index  at the end of a file will be replaced, but internal indices will
       not be consulted by SRF tools.

       The index is a hash table indexing the sequence names  only.  The  name
       itself  does not appear in the index, rather the top 7-bits of a 64-bit
       hash key are held in the index along with N-bits used to determine  the
       hash  bucket.  This  reduces  the  index size to around 10-15 bytes per
       sequence.

OPTIONS

       -c     Check only. This requests that the index is  not  produced,  but
              the  checks  performed  during the creation of an index (such as
              looking for duplicate sequence names) are still performed.

AUTHOR

       James Bonfield, Wellcome Trust Sanger Institute

                                 September 29                srf_index_hash(1)