From: |  | [log in to unmask][log in to unmask]>
>> Date: Thursday, April 5, 2007 3:42 am
>> Subject: Re: SPM5 slower with 4D files
>> To: [log in to unmask]
>>
>>
>> > Hi Jerome,
>> >
>> > yes, SPM will probably slower on 4D files than on 3D files. Also it will
>> > be slower on .nii files than on .hdr/.img pairs. The reason is, that for
>> > combined header and data files (as in 3D .nii and 4D cases) SPM needs
>> > something like random-write-access to your file to store small bits of
>> > information. This is more expensive in terms of I/O time (especially on
>> > large disks/RAID systems/network file storage) than storing 3D data with
>> > separate .hdr/.img files. However, storing one large file is more
>> > efficient in terms of disk usage (if you have partitioned/formatted your
>> > disk to efficiently store large files). In short, there is no free
>> > lunch, and you have to decide what is more important to you: saving time
>> > or saving disk space...
>> > I've just investigated this because I am doing a transition of our
>> > network filesystem away from NFS and had to resolve some performance
>> > issues as well.
>> >
>> > Volkmar
>> >
>> > On Wed, 4 Apr 2007, Paul Macey wrote:
>> >
>> >
>> > > Hi Jérôme
>> > >
>> > > I just wrote something to split 4D to 3D; run the attached
>> > >
>> > script
>> >
>> > > (cspm_im_4Dto3D, from SPM5 only) and it will prompt for a 4D
>> > >
>> > file to split.
>> >
>> > > You can also use it in batch mode with a couple more options
>> > >
>> > (see help). The
>> >
>> > > 3D files should be the same as in the 4D file, so I don't think
>> > >
>> > you will
>> >
>> > > loose anything by converting.
>> > >
>> > > Best wishes,
>> > > Paul
>> > >
>> > > Jérôme Redouté wrote:
>> > >
>> > > > Dear SPMers,
>> > > > My parameters estimation process oï˜Àx |
