Software support

Support

Frequently Asked Questions

Installation

Q. Can OxMetrics software be installed on a network?
Q. I installed under the Adminstrator account, why can other users not see the modules in GiveWin?
Q. Does network installation require administrator access?

Yes, OxMetrics software is able to run from a server over a network.

Because the OxMetrics software installs the module information under HKEY_CURRENT_USER in the registry, it will not be visible when installing under an administrator account, and then trying to run it under another account.

No, administrator access is not required. Below is some more detailed installation information.


The relevant installation information for GiveWin to work with its client modules such as PcGive, STAMP and TSP is stored in the registry. The module and other persistent information (most recently used files, etc.) for GiveWin is stored under HKEY_CURRENT_USER. Even a restricted user has access to this. Note that HKEY_CURRENT_USER is user specific.

Other important information is under HKEY_CLASSES_ROOT, this regards ActiveX automation (allowing PcGive and TSP to communicate with GiveWin) and file types (such as the .gwg file type). A user with restricted privileges has no access to this, so the network administrator has to replicate this information across users.

If the installation is done on a server to which the users connect from other computers, then the network admninstrator has tools to roll out the install the the user's registry. Subsequently, GiveWin will read HKEY_CLASSES_ROOT, but does not need write access. Then the HKEY_CURRENT_USER\GiveWin.2 key can also be installed (this contains the module information).

Updating the registry can also be done `by hand'. Modules can be made to register themselves with (for x: substitute the correct path):

    x:\givewin2\bin\givewin.exe /regserver
    x:\givewin2\bin\pcgive.exe /regserver
etc.
Modules do self register on start-up as well: if the user starts GiveWin from an icon, and then PcGive from an icon (or start menu), it will show next time in the modules list. The module information can be updated this way with restricted privileges, but permanent recording of the rest needs administrator rights (just once, so can be done by the administrator, especially when the registry information of the client machines is `reset' everytime).

Q. How does GiveWin use the Registry?

Under Windows persistent settings are stored in the system registry.

GiveWin automatically updates the registry settings when it is run. Givewin /regserver will just update the registry without running GiveWin.

The entries in HKEY_CLASSES_ROOT are for file types:

 .fl (GiveWin batch files)
 .in7 (GiveWin data files)
 .gwg (GiveWin graphics files)
and  
 GiveWin.2 (GiveWin server entry)
 OXMATED.OxMatEdCtrl.1(ActiveX matrix control - only used by PcNaive)
as well as entries in HKEY_CLASSES_ROOT\CLSID for automation and the ActiveX matrix control.

All persistent data is stored in HKEY_CURRENT_USER under Software\GiveWin.2\GiveWin including the list of available modules.

GiveWin will update the registry everytime it is run, to ensure that it is run properly. The entries in HKEY_CLASSES_ROOT cannot be set by users with restricted privileges. In that case, the system administrator has to ensure the program is properly installed.

The above registry entries can be created with the following commands:

    givewin /regserver
    regserver oxmated.ocx
using regserver.exe from GiveWin2\bin (or the system regsvr32). Most modules also support the /regserver command line argument.

Q. Clicking on PcGive results in ever more windows being opened!!??

We've had a few reports of this happening occasionally when the software is being run as a client from Terminal Server. We have no cure at this stage. However, the problem seems not to occur when PcGive (and other modules) is started from inside GiveWin. So we recommend this approach to avoid the problem.

Q. Why does PcNaive crash when an advanced DGP dialog is opened?

The error message is something like: `An unsupported operation was attempted'. This happens when the ActiveX control for the matrix editor is not installed correctly. To fix this, open a Command Prompt (MS-DOS) window, and locate the GiveWin\bin folder (the default would be C:\Program Files\GiveWin\bin). Then type:
    regserver oxmated.ocx
This should fix the problem when PcNaive is next run.

Ox

Q. `Cannot show draw window!' What does this mean?

There are two versions of Ox: Ox Professional and Ox Console. Ox Console cannot display graphics (but can save them to disk). Ox Professional, on the other hand, displays graphs in GiveWin. Whenever you see the `Cannot show draw window!' message in the output from Ox Console, there would have been a graph to see with Ox Professional.

Q. Does Ox have integers?
Q. I multiply two large positive integers in Ox, and the result is negative. Why?
Q. How do I compute factorials and binomial coefficients in Ox?

Ox has many variable types, including integers, double precision real values (`doubles'), matrices, strings, arrays of any types, objects, etc. The presence of integers and scalar doubles distinguishes Ox from many other matrix languages.
There are several reasons why Ox has integers:

  • addition, subtraction and multiplication are exact;
  • matrix indexing involves integers;
  • efficiency of single index operations.
The scalar double is mainly present for efficiency reasons.

In Ox, each expression has a type, e.g.:

  • concatenating two strings yields a string;
  • multiplying two matrices gives a matrix;
  • adding two integers gives an integer;
  • dividing two integers gives a double.
In languages with explicit type declaration (as in almost all low-level languages) the result of an expression is coerced into the type of the variable (so 2/3 will be 0 when assigned to an integer). In Ox, however, the type is determined implicitly, and a variable inherits the type of the expression. Therefore x becomes a double in x=2/3, while x="a"~"b" makes x a string.

All arithmetic on a computer has limitations, and Ox does not escape these. Integers range from -2^31 to 2^31-1 (the corresponding constants, defined in oxfloat.h, are INT_MIN and INT_MAX). When integer computations overflow or underflow, the result just wraps around. So, adding 1 to the largest integer gives the largest negative value! It is rare to encounter this in practice. One case I have been contacted about several times is recursive evaluation of the factorial function, n! = n!*(n-1)*...*1; 0! = 1. Successive multiplication by integers keeps the result as an integer, and, when overflow occurs, negative numbers could result.

The following program illustrates.

    #include <oxstd.h>
    factint(const n)
    {
        if (n <= 1)
            return 1;
        return n * factint(n - 1);
    }
    main()
    {
        for (decl i = 2; i < 18; ++i)
        {
            println("%3d", i, "! = ",
                "%15.15g", factorial(i),
                " ", factint(i));
        }
    }

The function factint calls itself recursively, until the integer 1 is returned. All subsequent multiplications involve integers, with the computations going wrong from 13! onwards (the correct numbers on the left-hand side are computed with the built-in function factorial, which was new in Ox 3.2):

  2! =               2 2
  3! =               6 6
  4! =              24 24
  5! =             120 120
  6! =             720 720
  7! =            5040 5040
  8! =           40320 40320
  9! =          362880 362880
 10! =         3628800 3628800
 11! =        39916800 39916800
 12! =       479001600 479001600
 13! =      6227020800 1932053504
 14! =     87178291200 1278945280
 15! =   1307674368000 2004310016
 16! =  20922789888000 2004189184
 17! = 355687428096000 -288522240

Switching to real numbers requires changing one line in the program:

    factdouble(const n)
    {
        if (n <= 1)
            return 1.0;
        return n * factdouble(n - 1);
    }

This allows the function to go much further, until 170! The floating point computations using doubles are also subject to limitations:

  • the largest value is approximately 1.79e+308;
  • when overflow occurs, the result is infinity;
  • about 15 of precision digits are available;
  • as a consequence there is an ε such that 1.0+ε=1.0; this is the machine precision, DBL_EPSILON (about 2.2e-16).
So when can only obtain the first 15 digits of the larger factorials (the magnitude of the outcome is, of course, correct).

Switching to doubles gave the factorial function a larger range. In most situations, the factorial is part of an expression which has an offsetting denominator. An example is the binomial coefficient. Computing 200!/(0!200!) using the factorial function results in .NaN, because it involves +.Inf/+.Inf. Using binomial(200,0) instead, gives the correct answer 1. A similar success could have been achieved with the loggamma function: log(n!) = logΓ(n+1), i.e. taking logs, and then the exponent: exp(loggamma(201) - loggamma(1) - loggamma(201))

DPD

Q. What does the `Warning: invertgen: singular matrix' message mean?

DPD/Ox uses generalized inverses in the estimation procedure. The following expression is used in the DPD code (line 1496 in version 1.21):

  mzhzinv = invertgen(mzhzinv, 30);    /* replace zhz by inverse */
In this statement: Sumi Zi'HiZi is inverted. The invertgen routine will print a warning if the matrix is singular, and continue with the generalized inverse. The most common situation in which this happens is when there are many GMM-type instruments.

Strictly there is no problem with this, and if the two-step coefficients are similar to the one-step coefficients, and both look reasonable compared to results for the same model from other estimators (eg. OLS levels, Within) then there is probably nothing to worry about. However this computational problem can be a signal that too many instruments are used (specifically, in some of the cross-section equations, relative to the cross-section dimension of your panel). It is advisable to check that the results are robust to using a smaller instrument set. Note that an option is available to print out the full instrument set, this can be helpful to understand what is happening, especially regarding the GMM instruments.

 


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