Hi! The issue you are experiencing seems to be due to record-marker length lack of interoperability.
In brief, AIUI, the problem is that Fortran standard specifications do not mandate any low level form for unformatted file I/O. Hence every compiler adopts its own form and *no* unformatted file interoperability is guaranteed between different Fortran compilers. Many compilers (including g77 <= 3.3 and ifort) have adopted the following low level structure for an unformatted record: START_MARK DATA END_MARK where START_MARK and END_MARK are two identical 32 bit signed integers that represent the record length (in bytes) and DATA is the actual record payload. In your case, START_MARK and END_MARK are the 32 bit signed integer representation of 12 (since your three integers make 12 bytes). This approach sets the maximum length of writeable/readable unformatted records to (2^31 - 1) bytes. To go beyond this limit some compilers exploit various backward-compatible techniques (based on the record-marker sign bit). Another way to go beyond this limit is using 64 bit signed integers as record-markers. This sets the limit to (2^63 - 1) bytes, which is fairly much more... This is the strategy adopted by g77 >= 3.4 and gfortran, which is unfortunately not backward-compatible, though... In your case, START_MARK and END_MARK are the 64 bit signed integer representation of 12, which is a 32 bit signed representation of 12 followed by a 32 bit signed representation of zero (remember that you are on i386, which is a little-endian architecture). When you read the file with a program which thinks that record-markers are 32 bit long, the second half of START_MARK is interpreted as if it were the first integer (hence i=0), then the first two actual integers are read (j=1 k=2) and the rest is ignored. OK, this should explain what happened (at least I hope so...). Now some news: This bug (lack of interoperability) seems to be fixed by upstream in gfortran 4.1.x (see http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19303 for details). I began to write a little C++ program to convert between different Fortran unformatted record-markers. I have a preliminary version that seems to work on little-endian machines (with little endian Fortran unformatted files): I can attach it if someone is interested. License is GNU GPL v2 only (the project got rejected by Savannah since I don't want to license it under any later version of the GNU GPL: see http://savannah.gnu.org/task/?func=detailitem&item_id=5204 if you're interested in all the gory licensing details). HTH. -- :-( This Universe is buggy! Where's the Creator's BTS? ;-) ...................................................................... Francesco Poli GnuPG Key ID = DD6DFCF4 Key fingerprint = C979 F34B 27CE 5CD8 DC12 31B5 78F4 279B DD6D FCF4
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