Reply-To: | | [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 Ý#Ìxx |