The Aggregate's helpme Utility

Audio Diagnostics for Clusters & Server Farms

Clusters and server farms often have many nodes... and very little hardware support for locating and diagnosing problems. Using the PC speaker, this less than 50K byte program allows a node to signal that it has a problem and describe the problem using arbitrary alphanumeric text.


Helpme is available as a single, self-contained, public domain C source code file, helpme.c. Precompiled versions that are statically linked using uClibc also are posted: helpme.useioctl.static (37804 bytes), helpme.useports.static (37644 bytes), and helpme.forcetoggle.static (37804 bytes) (whichever of these works best with your system should be renamed helpme and run as root). All of the above, along with HTML and text-only versions of this WWW page and a couple of musical tunes, also is posted as a compressed tar file: helpme.tgz or helpme.tar.bz2. Need more info? Read on....


Cluster supercomputers and server farms made using commodity PC hardware suffer from the combination of high component counts, high component failure rates, and relatively fragile interconnections between nodes: nodes will fail. Determining what has failed and why is complicated by the fact that most nodes have neither a console nor any other type of traditional status output device. Using a network connection to provide diagnostic information seems reasonable, but in practice it is common that the problem lies in the network card, cables, or switches.

Hardware manufacturers often provide diagnostic feedback using status lights, but that approach really isn't effective for nodes. Even if we had an alphanumeric display panel on each case, or a KVM switch connection and a monitor, identifying a "sick" node would require examining each node individually -- which is not practical for a large number of nodes. Manufacturers of PC motherboards instead use the PC speaker to output a "beep code" to help the user identify problems when no other I/O devices are functional. Because the audio signal from a single node may be able to be heard from a wide area within a room filled with nodes, audio signals are a better diagnostic output mechanism than per node displays. Unfortunately, vendor-specific "beep codes" are not very intuitive ways to convey diagnostic information.

This is why we built helpme: to serve as a cluster node diagnostic output mechanism. Rather than having a complex set of beep codes covering all the relevant status conditions, helpme uses a very simple beep code only to attract attention to the node and to express the urgency of the information. The actual status information is conveyed in the form of alphanumeric text rendered as an audio signal.

Given that the PC speaker does quite well producing beeps, it is not surprising that it is very effective rendering alphanumeric text as Morse code. In fact, using a somewhat higher pitch than most beep codes, the PC speaker provides a stunningly crisp rendition of dits and dahs. The patterns are so clear that they easily can be identified over the din of several racks of nodes. The relevant Morse code patterns are:

0: -----  A: .-    K: -.-   U: ..-   .: .-.-.-
1: .----  B: -...  L: .-..  V: ...-  ,: --..--
2: ..---  C: -.-.  M: --    W: .--   ?: ..--..
3: ...--  D: -..   N: -.    X: -..-  /: -..-.
4: ....-  E: .     O: ---   Y: -.--  +: .-.-.
5: .....  F: ..-.  P: .--.  Z: --..  *: ...-.-
6: -....  G: --.   Q: --.-           =: -...-
7: --...  H: ....  R: .-.
8: ---..  I: ..    S: ...
9: ----.  J: .---  T: -

The last few symbols are probably not very important for our purposes, but have been added to helpme in order to support the full standard Morse character set. Respectively, they represent period, comma, question mark (or request repeat), slash (or fraction bar), end of message (or cross or AR), end of work, and pause (or double dash).

Of course, the catch is that not everbody knows Morse code, so it would be nice to have another option....

The ideal would be to use the PC speaker for true text-to-speech voice synthesis, but the quality of PC speaker voice synthesis is mediocre at best, making it unreliable for conveying information as pure text-to-speech. Fortunately, we are far from the first people to be faced with this problem: the task of highly-reliable communication of alphanumeric data over noisy voice transmissions is common in military operations and air traffic control. The international standard solution for air traffic control is the NATO "Phonetic Alphabet" -- you know, that Alpha, Bravo, Charlie stuff. Even a very crude, low data rate, PC speaker software driver can reliably convey status information by pronouncing each character using the NATO-standard words (and their slightly unusual pronunciations, e.g., "Three" is pronounced "Tree", "Nine" is pronounced "Niner"):

0: Zero   A: Alpha    K: Kilo      U: Uniform
1: One    B: Bravo    L: Lima      V: Victor
2: Two    C: Charlie  M: Mike      W: Whiskey
3: Three  D: Delta    N: November  X: X-ray
4: Four   E: Echo     O: Oscar     Y: Yankee
5: Five   F: Foxtrot  P: Papa      Z: Zulu
6: Six    G: Golf     Q: Quebec
7: Seven  H: Hotel    R: Romeo
8: Eight  I: India    S: Sierra
9: Nine   J: Juliet   T: Tango

The PC speaker voice synthesis used in helpme is essentially 1-bit conversion using an 8KHz sample rate, yielding barely decipherable speech -- but that's good enough to clearly distinguish the NATO words. Ok, you'll do better if you listen to at least a few known phrases first just to get used to the audio defects, but it works. The very low data rate driver also means that the voice samples are very small. In fact, the enitre helpme program, supporting both Morse code and NATO phonetic alphabet, is well under 50K bytes as a fully self-contained program (no libraries, helper programs, nor files). Thus, helpme is suitable for ubiquitous use, even within single-floppy Linux distributions.

Use of helpme

As described above, helpme is not intended to be a general speech or sound facility. It is not compatible with any of the multitude of competing standards for such use. It also can be quite CPU intensive, making it highly undesirable if the CPU could be used for more productive work. Instead, helpme is intended to be a stand-alone audio diagnostic renderer for clusters and server farms, with a variety of features aimed at making it better suited to that task.

The input to helpme consists of ASCII text presented either as one or more command line arguments or as the standard input stream. If command line arguments are used, the arguments are treated as a single input separated by spaces. To allow for command line options, any command line argument that begins with - will be treated as an option specifier and omitted from the input.

Currently, there are a variety of command line options, three of which control properties of Morse rendering. The Morse options, and several other improvements over the original helpme, are intended to tune the Morse code rendering so that a user can more easily transcribe diagnostic messages. Even a novice can transcribe Morse code at the very slow default rate, but more skilled Morse users can tune the rendering to achieve their personal best transcription speed.

The input text is not just text, but uses a simple diagnostic message language to specify things like Morse or NATO rendering and repeats of a message. Since helpme is most useful for a node that has no other way of communicating, input syntax errors are simply ignored. The syntax is roughly:

input: phrase*

phrase: "(" phrase ")" repeat
      | item*

repeat: number
      | "*"      -- repeat forever

item: alphanumeric
    | " "        -- wordbreak pause (multiples are collapsed into one)
    | ","        -- wordbreak pause (incompressible) or Morse ","
    | "_" number -- set ms duration for tones (default 2000ms = 2 seconds)
    | "~" number -- play tone with number Hz frequency, 0 Hz is silent
    | ";"        -- equivalent to ~0
    | "-"        -- render using Morse code
    | "@"        -- render using NATO phonetic alphabet (also default)
    | "%"        -- toggle Morse code vs. NATO phonetic alphabet
    | "!"        -- urgent problem beep code
    | "?"        -- possible problem beep code or Morse "?"
    | "."        -- informational beep code or Morse "."
    | "/"        -- ignored in NATO, Morse "/"
    | "+"        -- ignored in NATO, Morse "+"
    | "*"        -- ignored in NATO, Morse "*"
    | "="        -- ignored in NATO, Morse "="

In the above grammar, number is any sequence of 0 or more digits and alphanumeric is any digit or letter. Uppercase and lowercase letters are treated identically and tab and newline are treated exactly like " ". Similarly, any of the commonly used grouping marks can be used instead of "(" and ")", so that any of "(<{[" can be paired with any of ")>}]". Note that punctuation marks are treated differently depending on the current choice of Morse or NATO rendering. Although some additional symbols may later be used for macro and/or comment facilities, generally, other characters are ignored. Here are a few example uses of helpme:

$ helpme PE42 -x OK.

Use the (default) NATO rendering of "Papa" "Echo" "Four" "Two", wordbreak pause, render "Oscar" "Kilo", and then make the informational alert sound. Notice that -x is ignored because it begins with a "-"; it is interpreted as a command line option, and there is no such option currently defined.

$ helpme '%PE42' -f13 OK. -h2000

Switch from the (default) NATO rendering to Morse, then render "PE42 OK." using Morse code with 2000Hz tones and "Farnsworth" speed of 13 WPM for characters and the default 5 WPM overall. Note that the position of options in the command line is irrelevant; all options are processed before any rendering is done.

$ helpme -w20

Make the urgent problem alert sound, then use the (default) NATO rendering of "November" "India" "Charlie", switch the default rendering, and repeat forever. Thus, "NIC" is alternately rendered as NATO and Morse versions. Notice that the * is treated as part of the loop syntax, not as the Morse punctuation character. Incidentally, the command line option causes the Morse to be rendered at a rather fast 20 WPM.

$ helpme '(1{2}34 5)6'

Use the (default) NATO rendering of "One", then render "Two" 34 times, then render "Five" (without a wordbreak pause), and repeat the entire sequence for a total of 6 times.

$ helpme

Use the (default) NATO rendering of "Alpha", pause for a single wordbreak, render "Bravo", pause for two wordbreaks, render "Charlie", set duration to 4 seconds, pause for 4 seconds, and render "Delta".

$ helpme

Set duration to 1/2 second, then play a tone with a frequency of 440Hz.

If you want, you can even play music with helpme. Here are Taps and Hornpipe. Ok, I didn't say it would sound good. ;-)

One minor technical detail to keep in mind: in this version, audio rendering does not begin until the entire input has been read. This was done because intermixing reads of the input with audio rendering would occassionally cause timing glitches that would make the audio rendering less understandable.

The Code

The full source code of helpme, helpme.c, is freely available as a full public domain release. The code as distributed only will work on an IA32 PC (Pentiums or Athlons of any flavor should work).

There are only three compilation options that you may want to alter:

To compile the program:

cc helpme.c -o helpme -O6
strip helpme

If you need helpme to be compiled to the absolute minimum image size, you probably will want to look at things like uClibc, a C library for embedded systems. Using this library and statically linking, a completely standaone helpme is less than 40K bytes! If you're really tight for space, bzip2 can compress that file to about 20K bytes.

The use of ioctl() calls requires access permission on /dev/console, which usually requires root priviledges for a process not using the console as its standard input. If you instead tell helpme to use direct accesses to I/O ports, it needs access rights to those ports and also permission to temporarily disable interrupts around some critical I/O code, again requiring root priviledges. Thus, either way, helpme generally must run with root priviledges. Once compiled, you can mark it as set uid root by executing the following two commands while logged-in as root:

chown root helpme
chmod +s helpme

Because helpme has been placed in the public domain, it is entirely up to you to determine fitness for your application. Neither the author, Prof. Hank Dietz, nor the University of Kentucky, are to be held responsible for any problems that may occur. That said, we will try to fix reported bugs (in our copious spare time ;-).

Version History

20020910: The initial release. There are no known bugs at the time of release.

20020920: The original version used the hardware timestamp counter to do highly-precise timing... but that level of precision really isn't needed. Using gettimeofday() is about 1000X less accurate, but is still good enough. This change also allowed all the unsigned long long stuff to become unsigned int. The Morse code support also was made more compliant with standards and three command line options were added: -h to specify the Morse tone frequency in Hz, -w to specify the Morse speed in words per minute, and -f to set "Farnsworth" timing (sending dots and dashes at a higher rate with spaces at a lower rate). The defaults are -h1500 -w5 -f5. The -w5 default is MUCH slower than in 20020910; a more proficient Morse user would want -w13 or higher. Specifying -w5 -f13 gives a novice the sound of 13 WPM, but with spaces enlarged for an overall speed of 5 WPM. Three other options also were added: -v adds the version as though "20020920 " were typed, -n adds the hostname up to the first ".", and -- means read the standard input even if there was stuff to render on the command line. There also were a number of coding changes made to reduce size of the program.

20021009: A few typos corrected on this WWW page. The corrections will be echoed in the next version.

20021024: A few more typos corrected on this WWW page. The corrections will be echoed in the next version.

References (actually more like a mini-FAQ)

Morse code was developed by Samuel Morse in the 1840s. As described here, the original Morse code was somewhat different from what we use now, which should more correctly be called something like "International Morse Code."

A "Phonetic Alphabet" as we describe it here is not a set of phonetic symbols to describe the sounds in a language, but rather a set of words that can be used to more clearly distinguish the individual letter each word represents. This type of phonetic alphabet seems to have originated in military applications, probably around 1900. The particular set of words we use is the one that, according to this US Navy History, was adopted in 1957. From sometime in the 1950s, it has been the standard for NATO (North Atlantic Treaty Organization), ICAO (International Civil Aviation Organization), ITU (International Telecommunications Union), and the FAA (Federal Aviation Administration). It also is commonly used for radio call signs, etc. From it's military heritage, especially NATO naval signal codes, a few idiomatic sequences have commonly known special meanings. For example, "Bravo Zulu" means "well done." Another common idiomatic phrase is "Sierra Hotel" for "extremely capable" (according to this, it is really an abbreviation for "Sh*t Hot").

In case you are wondering which voice synthesis packages were considered before going with Morse and NATO rendering of text, there are really only two freely available alternatives that seemed viable. The most practical alternative seems to be rsynth 2.0, which is fairly compact and sounds a lot like the old Votrax synthesizer (but doesn't need any special hardware). Festival is a newer system that seems much more capable, but it also is significantly harder to strip down for standalone use in an audio diagnostic renderer. Of course, there are many other systems freely available, including: KPE80 - A Klatt Synthesiser and Parameter Editor, Emacspeak, FreeTTS, and Flite (festival-lite, a simplified Festival that, when stripped and compressed by bzip2 fits in 2.5MB). In fairness, the text-to-speech stuff really isn't all that bad in itself, but by the time the sound is passed through a random PC's speaker (even using 8-bit PWM), the combination of defects makes it very difficult to understand. Add to that the fact that you'll be listening in a rather noisy machine room and it just isn't good enough. In fact, even when I recorded myself saying various text phrases and played that back, it was very difficult to catch every word.

The code for using the PC speaker has a bit of a history. Back in 1994, we developed a multi-voice music compiler to generate code that would play the music using the PC speakers on the nodes of our Linux PC clusters. It was done as a demonstration of the cheap barrier synchronization and global functions supported by aggregate function communication: each new note was randomly assigned to a different node in the cluster, which all nodes agreed upon. In fact, early versions barrier synchronized with each toggle of a PC speaker. Many better PC speaker drivers have been built since 1994, including a variety of ways to make the PC speaker appear to be an 8-bit sound card (clever uses of 8-bit PWM), but these techniques require lots more data and really do not improve the sound quality all that much. Thus, the only newer stuff that we've really used is the Linux kernel support for ioctl().

Where did the NATO audio data come from? Me. I recorded myself using Microsoft .wav files, 8-bit, 8K samples/second, in my too-noisy office using a laptop PC. I wrote simple (and ugly) software to convert the .wav files into various compressed formats. After trying quite a few variations on both desktop and laptop PCs, I found that the more expensive methods actually sounded slightly better on some machines, but far worse on others. Run-length encoded 1-bit data, still at 8K samples/second, wasn't great on any machine... but it wasn't terrible on any machine either, and it is very compact. That's how the tables you see in helpme.c are encoded. Although I doubt I'll change the encoding, it is quite possible that a future version will replace those tables with an improved set of recordings....

Why is the program called helpme? Remember the original Star Trek Episode 77: The Savage Curtain? In that episode, Surak is captured and apparently screams out in pain "Help Me, Spock!" Lincoln goes to rescue him and discovers that Surak already was dead, and the evil aliens demonstrate how they imitated Surak's voice, and then how they will imitate Lincoln's voice saying "Help Me, Kirk!" once he's dead. Since helpme essentially calls for help for a dead or injured node of a cluster or farm, this name seemed as appropriate as anything else we could think of. It also conveys the idea that this tool only should be used in such desperate situations; it is not intended as a general-purpose audio interface.

Author Contact Info

If you have any questions or comments, contact:

Professor Hank Dietz, James F. Hardymon Chair in Networking
College of Engineering
Electrical and Computer Engineering Department
453 Anderson Hall
(Office 469 Anderson Tower, Lab 672 Anderson Tower)
Lexington, KY 40506-0046

Office Phone: (859) 257 4701
Lab Phone:    (859) 257 9695
Fax :         (859) 257 3092
Home URL:

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The Aggregate. The only thing set in stone is our name.