So now that cvs is reachable again I have confirmed that
the code segment
 
     } else if (obj->InheritsFrom( "TH1")) {
 
       // still don't know how to do TH1s

is indeed still present.
If you want me to look at this some more, you need to provide some code to exhibit the problem.

John.

> > The current h1_book() macros (and the previous example analyzer code) have an
> > odd persistency problem: for example, the user wants to change some histogram
> > limits, edits the h1_book() calls, rebuilds and restarts the analyzer, starts a
> > new run, and observes that all histograms are filled using the old limits, his
> > changes "did not take". The user panics, I get paged during the Holy Lunch Hour,
> > everybody is unhappy.
> > 
> > This is what I think happens:
> > 
> > 1) analyzer starts
> > 2) LoadRootHistgrams() loads old histograms from file
> 
> I can't get onto cvs@midas.psi.ch right now
> (cvs update
> cvs@midas.psi.ch's password: 
> Permission denied, please try again.)
> 
> but when I changed LoadRootHistograms a few days ago I left it as:
> 
>     } else if (obj->InheritsFrom( "TH1")) {
> 
>       // still don't know how to do TH1s
> 
> so h1_book() is creating the first and only copy of the histograms.
> I am able to create new histogram limits.
> I don't get the memory leak problems.
> 
> However I have seen the memory leak problems before, and they are real.
> They must be dealt with either by (1) first deleteing the old histogram
> or (2) ensuring that histogram names are unique in the whole application
> (different modules/folders can not use the same histogram names).
> 
> I will return to this once I can do a cvs update for midas.
> 
> John.
> 
> > 3) user code calls h1_book()
> > 4) h1_book template in midas.h does this (roughly):
> >       hist = (TH1X *) gManaHistosFolder->FindObjectAny(name);
> >       if (hist == NULL) {
> >          hist = new TH1X(name, title, bins, min, max);
> > 5) since the histogram already exists (loaded from the file, with the old
> > limits), the TH1X constructor is not called at all, new histogram limits are
> > utterly ignored.
> > 
> > A possible solution is to unconditionally create the ROOT objects, like I do in
> > the example code posted at <a
> href="<a
href="http://dasdevpc.triumf.ca:9080/Midas/191">http://dasdevpc.triumf.ca:9080/Midas/191</a>">http://dasdevpc.triumf.ca:9080/Midas/191"><a
href="http://dasdevpc.triumf.ca:9080/Midas/191</a>">http://dasdevpc.triumf.ca:9080/Midas/191</a></a></a>.
> That code
> > produces an annoying warning from ROOT about possible memory leaks. This could
> > be fixed by adding a two liner to "find and delete" the object before it is
> > created, trippling the number of user code lines per histogram (find & delete,
> > then create). Highly ugly.
> > 
> > midas.h macros (h1_book & co) can be fixed by adding checks for histogram limits
> > and such, but I would much prefer a generic solution/convention that would work
> > for arbitrary ROOT objects without MIDAS-specific wrappers (think TProfile,
> > TGraph, etc...).
> > 
> > Any suggestions?
> > 
> > K.O.

> > I can't get onto cvs@midas.psi.ch right now
> > (cvs update
> > cvs@midas.psi.ch's password: 
> > Permission denied, please try again.)

cvs@midas.psi.ch should be up and running again.

> I can't get onto cvs@midas.psi.ch right now
> (cvs update
> cvs@midas.psi.ch's password: 
> Permission denied, please try again.)

I had to upgrade midas.psi.ch today with Scientific Linux 3.03. Most things are back to work, but
 I failed to do the anonymous CVS account. I have to wait for next week when the experts are
there. I will let you know when it's working again.

- Stefan

> The current h1_book() macros (and the previous example analyzer code) have an
> odd persistency problem: for example, the user wants to change some histogram
> limits, edits the h1_book() calls, rebuilds and restarts the analyzer, starts a
> new run, and observes that all histograms are filled using the old limits, his
> changes "did not take". The user panics, I get paged during the Holy Lunch Hour,
> everybody is unhappy.
> 
> This is what I think happens:
> 
> 1) analyzer starts
> 2) LoadRootHistgrams() loads old histograms from file

I can't get onto cvs@midas.psi.ch right now
(cvs update
cvs@midas.psi.ch's password: 
Permission denied, please try again.)

but when I changed LoadRootHistograms a few days ago I left it as:

    } else if (obj->InheritsFrom( "TH1")) {

      // still don't know how to do TH1s

so h1_book() is creating the first and only copy of the histograms.
I am able to create new histogram limits.
I don't get the memory leak problems.

However I have seen the memory leak problems before, and they are real.
They must be dealt with either by (1) first deleteing the old histogram
or (2) ensuring that histogram names are unique in the whole application
(different modules/folders can not use the same histogram names).

I will return to this once I can do a cvs update for midas.

John.

> 3) user code calls h1_book()
> 4) h1_book template in midas.h does this (roughly):
>       hist = (TH1X *) gManaHistosFolder->FindObjectAny(name);
>       if (hist == NULL) {
>          hist = new TH1X(name, title, bins, min, max);
> 5) since the histogram already exists (loaded from the file, with the old
> limits), the TH1X constructor is not called at all, new histogram limits are
> utterly ignored.
> 
> A possible solution is to unconditionally create the ROOT objects, like I do in
> the example code posted at <a
href="http://dasdevpc.triumf.ca:9080/Midas/191">http://dasdevpc.triumf.ca:9080/Midas/191</a>.
That code
> produces an annoying warning from ROOT about possible memory leaks. This could
> be fixed by adding a two liner to "find and delete" the object before it is
> created, trippling the number of user code lines per histogram (find & delete,
> then create). Highly ugly.
> 
> midas.h macros (h1_book & co) can be fixed by adding checks for histogram limits
> and such, but I would much prefer a generic solution/convention that would work
> for arbitrary ROOT objects without MIDAS-specific wrappers (think TProfile,
> TGraph, etc...).
> 
> Any suggestions?
> 
> K.O.

The current h1_book() macros (and the previous example analyzer code) have an
odd persistency problem: for example, the user wants to change some histogram
limits, edits the h1_book() calls, rebuilds and restarts the analyzer, starts a
new run, and observes that all histograms are filled using the old limits, his
changes "did not take". The user panics, I get paged during the Holy Lunch Hour,
everybody is unhappy.

This is what I think happens:

1) analyzer starts
2) LoadRootHistgrams() loads old histograms from file
3) user code calls h1_book()
4) h1_book template in midas.h does this (roughly):
      hist = (TH1X *) gManaHistosFolder->FindObjectAny(name);
      if (hist == NULL) {
         hist = new TH1X(name, title, bins, min, max);
5) since the histogram already exists (loaded from the file, with the old
limits), the TH1X constructor is not called at all, new histogram limits are
utterly ignored.

A possible solution is to unconditionally create the ROOT objects, like I do in
the example code posted at http://dasdevpc.triumf.ca:9080/Midas/191. That code
produces an annoying warning from ROOT about possible memory leaks. This could
be fixed by adding a two liner to "find and delete" the object before it is
created, trippling the number of user code lines per histogram (find & delete,
then create). Highly ugly.

midas.h macros (h1_book & co) can be fixed by adding checks for histogram limits
and such, but I would much prefer a generic solution/convention that would work
for arbitrary ROOT objects without MIDAS-specific wrappers (think TProfile,
TGraph, etc...).

Any suggestions?

K.O.

With recent changes to mana.c, creation of user ROOT objects in the MIDAS
analyser has changed. Here is the new example code for creating ROOT objects
that are visible in ROODY and are saved into the histogram file.

1) in the "global" context (outside of any function)

#include <TH1D.h>
#include <TProfile.h>

static TH1D* gMyHist1 = 0;
static TProfile* gMyHist2 = 0;

2) In the analyzer "init" or "begin run" method, create the histogram:

//extern TFolder *gManaHistosFolder; // from midas.h
gMyHist1 = new TH1D("gMyHist1",...);
gMyHist2 = new TProfile("gMyHist2",...);
gManaHistosFolder->Add(gMyHist1);
gManaHistosFolder->Add(gMyHist2);

(note: this will produce an warning about "possible memory leak")

3) In the per-event method, fill the histograms

gMyHist1->Fill(x);
gMyHist2->Fill(x,y);

4) In the Makefile, where you compile the frontend, add "-DUSE_ROOT" right after
"-I$(ROOTSYS)/include"

K.O.

I preliminary implemented NaNs into the history system. It works such that if a
device driver returns a read error status, the class driver writes a NaN
(Not-a-Number) into the corresponding variable via the new function ss_nan(). The
"mhist" utility directly displays these as "nan" (Linux) or "-1.#IND00" under
Windows, indicating the error status. The history display via mhttpd just skips
these values (see elog:/1). I think this is better than showing just zero values,
because in most cases zero is a valid measurement and could confuse people.

Of course it is not enough just having "gaps" in the history display, so it's
important that the corresponding device driver issues an error message, which could
even trigger an alarm.

I have tested this under Windows, but only compiled under Linux. The only class
driver I modified so far is "multi.c". People should have a look, make some tests,
and let me know if this is a good thing, or if we should change it somehow.

- Stefan

Dealing with the NaN's in the history system in the past week, a question came
up at PSI about how to deal with invalid history data.

Assume you have several devices going into one history equipment, and one device
has a problem, such that it cannot be read. In the past, the device driver
system returned zero, which was written to the history file. While this is ok in
some cases, it might not be in others, where zero is maybe a valid measurement.
Furthermore, it might confuse some regulations loops.

An alternative is to keep the last correctly measured value. As long as the
device has its problem, the value is kept. However, values are written to the
history system which might look like valid, although they are not. So what about
writing explicitly NaNs to the history system? For the display routine the NaNs
could be omitted, leaving blank regions where no valid measurement is available.
Or one could explicitly mare the region as invalid. Konstantin, do you know how
to write NaN explicitly to a float variable? And what do the others think about
these possibilities?

- Stefan

> Could someone please explain to me how cm_msg, cm_msg1, etc. all work.  The
> documentation is very terse.  
> 
> I want to setup a fairly significant set of debugging, and error messages for a
> new frontend.  I need to get these messages to a logging file.  I also would
> like to get the error messages to the user through whatever interface Midas
> normally uses for error reporting.  

For errors, use

  cm_msg(MERROR, "routine_name", "Your error message, code=%d", i);

This produces an error message which is logged to midas.log, and distributed to all
clients which have called cm_msg_register(). For example odbedit will just print
that message. The syntax of the second half of cm_msg is the same as for printf(),
so you can add format specifiers and variable arguments as you do for printf(). The
first argument is the message type (MDEBUG for example is only distributed but not
logged). 

For a more detailed list of message types, please refer to

http://midas.triumf.ca/doc/html/AppendixE.html#midas_macro

Could someone please explain to me how cm_msg, cm_msg1, etc. all work.  The
documentation is very terse.  

I want to setup a fairly significant set of debugging, and error messages for a
new frontend.  I need to get these messages to a logging file.  I also would
like to get the error messages to the user through whatever interface Midas
normally uses for error reporting.  

Jan

> > - system.c: do not chdir("/") in ss_daemon_init()- it prevents us from ever
> >   getting core dumps from midas daemons.
> 
> The chdir("/") is from one of the unix text books. They say you HAVE to do it. If you start a
> daemon on an NFS file system, you cannot unmount that file system as long as the daemon is
> running.

Right, I remember this NFS problem from a while back.

This problem does not exist in the current crop of Linux systems (since Red Hat 7.3 at least) - they
either kill off all user programs or use "umount -f" and "umount -l".

"umount -l" works in any case to unmount a "busy" filesystem.

For systems where the NFS problem does still exist, one should do this: "mlogger -D" becomes "(cd /; mlogger -D)".

So I suspect that the "cd /" advice from the unix programming book is no longer as necessary
as it used to be. (Perhaps a better advice would have been to "cd /tmp", so we could still get
core dumps from non-root daemons).

K.O.

> When i compile the experiment example of 1.9.5 the problem happened:
> 
> adccalib.c: In function `INT adc_calib_init()':
> adccalib.c:114: `H1_BOOK' undeclared (first use this function)
> adccalib.c:114: (Each undeclared identifier is reported only once for each
>    function it appears in.)
> make: *** [adccalib.o] Error 1
> 
> my ROOT is 4.01 and Zlib is 1.2.2

We're in the process of fixing in the proper manner this problem, in the mean time
please add to the analyzer makefile the definition: -DUSE_ROOT at the line:
...
ROOTCFLAGS += -DHAVE_ROOT -DUSE_ROOT

When i compile the experiment example of 1.9.5 the problem happened:

adccalib.c: In function `INT adc_calib_init()':
adccalib.c:114: `H1_BOOK' undeclared (first use this function)
adccalib.c:114: (Each undeclared identifier is reported only once for each
   function it appears in.)
make: *** [adccalib.o] Error 1

my ROOT is 4.01 and Zlib is 1.2.2

> What is the api call to determine the index of the frontend when specifying the
> -i parameter during execution of the frontend? 

INT get_frontend_index();

- Stefan

> - system.c: do not chdir("/") in ss_daemon_init()- it prevents us from ever
>   getting core dumps from midas daemons. The old behaviour is trivially
>   restored by "cd /" before starting the daemon; or by "limit coredumpsize 0".

The chdir("/") is from one of the unix text books. They say you HAVE to do it. If you start a
daemon on an NFS file system, you cannot unmount that file system as long as the daemon is
running. I'm sure the same code is inside most other daemons (apache, ...). So if we go away
from that standard, we have to be aware of the consequences.

What is the api call to determine the index of the frontend when specifying the
-i parameter during execution of the frontend? 

> > I am commiting MIDAS modification accumulated...

mhttpd changes:

- Renee's improvements on http transaction logging
- Implement "minimum" and "maximum" clamping for history graphs. Unfortunately
  there is no GUI code for changing the "minimum" and "maximum" settings,
  other than directly frobbing the odb.
- When making history graphs, detect NaNs in the history data.
(- status page code for the TWIST event builder (precursor of the standard
   event builder) stays uncommited).

K.O.

> I am commiting MIDAS modification accumulated during the last few months of running TWIST:

More:
- mfe.c: in error messages "cannot find statistics record", also print
  the name of the record we are looking for.
- mlogger.c: in warning message "Write operation took N ms", report the name
  of the offending data stream.
- system.c: do not chdir("/") in ss_daemon_init()- it prevents us from ever
  getting core dumps from midas daemons. The old behaviour is trivially
  restored by "cd /" before starting the daemon; or by "limit coredumpsize 0".
- odb.c: db_validate_db() detect and break infinite looping on free list corruption.

K.O.

I am commiting MIDAS modification accumulated during the last few months of running TWIST:
1) system.c::ss_shm_open() fail if trying to map a file that is smaller than we expect.
2) midas.c::bm_lock_buffer(), el_submit(), el_delete_message(): do not wait for mutexes forever, use a 5 
minute timeout. If we can't get the lock, cm_msg()/abort().
The above helps dealing with complete midas freezes. I also have code to keep track of "who locked
the mutex *and* is still holding it?!?" but it is way too ugly to commit. I wish we had a "lockedByPid"
entry for all lockable objects.
K.O.
 

>    We've had mhttpd aborting regularly since upgrading from midas-1.9.3.  This
> happens during elog queries, and is due to an elog file that was incorrectly
> modified by hand.

(sorry for delayed reply, for reasons unknown, I did not get an email notice when this was posted)

Yes, I agree, error handling in midas elog code is insufficient (note missing error checks for
read() and lseek() system calls). Anything but "perfect" elog files would cause funny errors and
malfunctions.

>  The modification to the file occurred 6 months ago.
>    el_retrieve(midas.c:15683) now has several assert statements, one of which
> aborts the program on reading the bad entry.

I added those to fix problems with "broken last NN days" and with infinite looping in the elog code
that we observed in TWIST.

You are welcome to replace the assert() statements with proper error handling. I used to have some code
that could report the filename of the bad elog file. Can we also report the exact file location for broken
files.

Please send me the diff, I will commit it to midas cvs.

>    Why is assert used, instead of an error return from the function (if
> necessary), and maybe an error message in the log file?  Assert statements are
> often removed, using NDEBUG, for normal use.

I use assert() in several ways:

0) I want a core dump each time X happens. (This is the only reasonable action when facing memory/stack
corruption. The problems in the elog code were stack corruption).
1) "I am too lazy to write proper error handling code" so I just crash and burn. This includes the
case where "proper error handling" would be "too invasive".
2) the error is too bad (or too deep) and there is no reasonable way to recover. Print an error message
and dump core (for later analysis). I sometimes use "cm_msg(); abort()". (assert is "printf("error"); abort()")

Please refer to literature for philosophic discussions on uses of assert() (Argh! Stefan will have my
head again!), but I will mention that "abort() early, abort() often" I find very effective. BTW, this technique
is heavily used in the Linux kernel (oops(), bug(), panic()) with some good effect, too.

>    The problem elog entry had one character removed, so end-of-file came before
> the end of the message.  This could probably occur without the file being
> altered, if the disk containing the elog fills.

Yes, I think you are right. In TWIST, we have seen disk-full conditions break both elog and history.

K.O.