You are all extremely informed and clever!! This file is part of an old archive of haemoglobin structures from the 1990s. I suspect they are all generated on a VAX from lcf files when I was "updating" the archive..
So now if I have the character I can update them all again, in the unlikely event that someone will want to use them! Thank you all very much Eleanor On Wed, 14 Nov 2018 at 14:41, Zhijie Li <zhijie...@utoronto.ca> wrote: > Hi Nick, > > > I think I've found the machine stamps in the ccp4 lib (Ian Tickle directed > me to the C programs folder yesterday. Thanks Ian): > > > ccp4_ssydep.h > > #define DFNTI_MBO 1 /**< Motorola byte order 2's compl */ > #define DFNTI_IBO 4 /**< Intel byte order 2's compl */ > > #define DFNTF_BEIEEE 1 /**< big endian IEEE (canonical) */ > #define DFNTF_VAX 2 /**< Vax format */ > #define DFNTF_CONVEXNATIVE 5 /**< Convex native floats */ > #define DFNTF_LEIEEE 4 /**< little-endian IEEE format */ > > > Checking the numbers are quite feasible for MTZ files (not maps because we > can put anything into MRC/ccp4 map). Yes, the idea is to try all > possibilities until we can recover miller indices that look normal. > > Zhijie > > ------------------------------ > *From:* Nicholas Devenish <ndeven...@gmail.com> > *Sent:* Wednesday, November 14, 2018 9:29 AM > *To:* Zhijie Li > *Cc:* CCP4BB@jiscmail.ac.uk > *Subject:* Re: [ccp4bb] VERY old mtz file.. > > Hi Zhijie, > > Thanks for the answer. I'd read http://www.ccp4.ac.uk/html/mtzformat.html > "The first 4 half-bytes represent the real, complex, integer and character > formats, and the last two bytes are currently unused" - and assumed that a) > formats meant size, given that it was (4,4,4,1) in files I'd seen, though > perhaps parsers don't really seem to use this. and that b) while this > doesn't specify endian-ness, one could infer it from whether the two unused > zero-bytes came in the little-or-big end of the integer. Otherwise there > really isn't an encoded way to tell if the file was written little or big > other than guessing and checking if the numbers are sensible? > CCP4 Program Suite: mtz format <http://www.ccp4.ac.uk/html/mtzformat.html> > www.ccp4.ac.uk > Column types. All columns in an MTZ file are assigned a type, taken from > the following list. The LABIN line of a particular job connects columns in > an input MTZ file with the columns expected by the program. > > > > Perhaps this is a (small) flaw in the spec, though nowadays almost > everyone seems to have moved to little-endian. > > Nick > > On Wed, Nov 14, 2018 at 2:13 PM Zhijie Li <zhijie...@utoronto.ca> wrote: > > > > Hi Nick, > > > > > > I guessed the machine stamp from MRC/CCP4 format description - half byte > 01 means BE, half byte 04 means LE. Are these only applicable to intel > machines? How are other machine architectures indicated? I do not know. We > probably can find the authoritative answer from the CCP4 library, just need > a little bit more time... > > > > > > The machine stamp itself should not be affected by the machine's > architecture, because it needs to be read before the program knows what the > architecture is. Therefore it should be a string instead of a number. In > the MRC/CCP4 map specification, it says that only the first two bytes are > used. I had seen some home-brew programs taking shortcuts by using the int > value of the machine stamp word, and I thought that was smart. Now I > realise that this practice has the risk of failing on non-intel machines. > So, if it is meant to be half-bytes, interpret it as half bytes! > > > > > > Zhijie > > > > > > > > ________________________________ > > From: Nicholas Devenish <ndeven...@gmail.com> > > Sent: Wednesday, November 14, 2018 8:54 AM > > To: Zhijie Li > > Cc: CCP4BB@jiscmail.ac.uk > > Subject: Re: [ccp4bb] VERY old mtz file.. > > > > Hi Zhijie, > > > > Looks like we both had the same thoughts! > > > > On Wed, Nov 14, 2018 at 1:19 PM Zhijie Li <zhijie...@utoronto.ca> wrote: > > > > The semi....BE.mtz has the big endian stamp (0x11 11 00 00 at bytes 9-12 > ) put in the header of the original file; everything else is untouched > > > > > > Is this correct? I thought machine stamp was supposed to be the 4-bit > sizes of int, real, complex and char e.g. all the little endian MTZ's I've > seen have 0x44 41 00 00, which would make the big-endian version 0x00 00 41 > 44. Then again, mtzdmp complained regardless, and perhaps I've just > misinterpreted the documentation (I'd love to know if this was the case!) > > > > Thanks, > > > > Nick > > > > ------------------------------ > > To unsubscribe from the CCP4BB list, click the following link: > https://www.jiscmail.ac.uk/cgi-bin/webadmin?SUBED1=CCP4BB&A=1 > ######################################################################## To unsubscribe from the CCP4BB list, click the following link: https://www.jiscmail.ac.uk/cgi-bin/webadmin?SUBED1=CCP4BB&A=1
