On Thu, 20 Dec 2007, Manoj Rajagopalan wrote:
> Does anyone know what outputs the *.00.h5 files store and what the
> *.50.h5 store? I have only one f.output_hdf5 statement in my program
> (fields f). Is one for the electric field and the other for the magnetic
> field since they are computed at different half-steps of each step?
The number in the filename is the time (in meep c/a units) to two decimal
places. For example:
ring-ez-000305.25.h5
is the Ez field from ring.ctl at time 305.25. If you look in the C++
code, this filename is set in fields::h5file_name.
Now that I think about it, I'm not sure this naming convention is always
the best idea. Since the units in Meep are arbitrary, it is possible to
set the lengthscales so that the time step is < 0.01 ... in this case you
might have a problem because files from different time steps will have the
same name. (Alternatively, if the timestamp is too large then it is
annoying because the filenames could get rather long and of variable
length so that they don't sort properly.)
I never noticed this before because we always recommend using natural
units of distance, so that your wavelength is of order unity ... in this
case, for any reasonable resolution the timestep is normally going to be
at least 0.01. (Or even if you crank up the resolution to be extremely
large, you probably aren't going to output h5 files every timestep.)
For the next Meep release, I'll change it so that if the time step is <
0.01 or too large then the filename uses the integer timestep count as a
timestamp instead of the time. Otherwise, it will stick with the current
behavior (which is convenient since that way the filenames are independent
of resolution). If anyone needs the patch now, I've attached it below.
(It is also possible to completely control the output filename manually if
you use lower-level functions, of course.)
Regards,
Steven G. Johnson
--- old-meep/src/h5fields.cpp 2007-12-21 19:55:23.480617059 -0500
+++ new-meep/src/h5fields.cpp 2007-12-21 19:55:23.771574190 -0500
@@ -416,7 +416,12 @@
static char filename[buflen];
char time_step_string[32] = "";
- if (timestamp) snprintf(time_step_string, 32, "-%09.2f", time());
+ if (timestamp) {
+ if (dt >= 0.01 && dt < 10)
+ snprintf(time_step_string, 32, "-%09.2f", time());
+ else
+ snprintf(time_step_string, 32, "-%09d", t);
+ }
snprintf(filename, buflen, "%s/" "%s%s" "%s" "%s" ".h5",
outdir,
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