Saint's Log

9Jul/100

Changing Screen Resolution of Ubuntu in Virtual Box

As suggested on one of the Ubuntu forums, the key here is to install the VirtualBox guest  additions. Having done so on my system, I ran these commands:

cd /media/VBOXADDITIONS_3.2.6_63112/
sudo ./VBoxLinuxAdditions-x86.run

Rebooting my virtual machine and maximizing the VirtualBox window left me running Ubuntu at my native screen resolution of 1680x1050 :).

Update: On VirtualBox 4.1.2, use the virtual machine's Devices -> Install Guest Additions ... menu item. The ISO Disc should be automatically mounted, and allowing autorun to continue should complete the installation. The Virtualbox website has more information on guest additions.

8Jul/100

Excel Macro to Merge First Two Cells of Each Column

Once in a while you may run into an Excel spreadsheet in which the first two rows have been used for column labels as a way to wrap text. Cleaning this up involves the straightforward task of merging the first two cells of each column. This rather tedious task is thankfully easily automated with an Excel VBA macro. See the code samples below:

Sample 1:

Sub MergeFirstTwoCellsInEachColumn()
    ' Bound the range selection as Ctrl+End would.
    ' See http://www.ozgrid.com/forum/showthread.php?t=17070
    Dim lastCol As Integer
    Dim row1LastCol As Integer
    Dim row2LastCol As Integer

    row1LastCol = Range("A1").currentRegion.End(xlToRight).Column
    row2LastCol = Range("B1").currentRegion.End(xlToRight).Column

    lastCol = WorksheetFunction.Max(row1LastCol, row2LastCol)

    ' Select the first two rows
    Rows("1:2").Select

    ' Merge the first two cells of each column
    For i = 1 To lastCol
        Dim columnCells

        columnCells = Selection.Columns(i).Cells

        Dim finalColumnText

        ' Concatenate contents of cells in rows 1 and 2 in this column
        ' separating them with a space
        finalColumnText = Trim(columnCells(1, 1) & " " & columnCells(2, 1))

        ' Clear both cells and store the new value in the first cell
        Selection.Columns(i).Value = ""
        Selection.Columns(i).Cells(1, 1) = finalColumnText

        ' Merge the cells
        Selection.Columns(i).Merge
    Next i
End Sub

One side effect of this code is that it merges cells in the columns up to the end of the range that would be selected if you pressed Ctrl + End. The columns to the right of this range are not merged, in effect leaving two rows in the spreadsheet for the headings. Enter Sample 2:

Sub MergeFirstTwoCellsInEachColumn2()
    ' Select the first two rows
    ' Bound the range selection as Ctrl+End would.
    ' See http://www.ozgrid.com/forum/showthread.php?t=17070
    Dim lastCol As Integer
    Dim row1LastCol As Integer
    Dim row2LastCol As Integer

    row1LastCol = Range("A1").currentRegion.End(xlToRight).Column
    row2LastCol = Range("B1").currentRegion.End(xlToRight).Column

    lastCol = WorksheetFunction.Max(row1LastCol, row2LastCol)

    ' Select the first two rows
    Rows("1:2").Select

    ' Combine the contents of the first two cells of each column
    For i = 1 To lastCol
        Dim columnCells
        Dim finalColumnText

        columnCells = Selection.Columns(i).Cells

        ' Concatenate contents of cells in rows 1 and 2 in this column
        ' separating them with a space
        finalColumnText = Trim(columnCells(1, 1) & " " & columnCells(2, 1))

        ' Store the new value in the first cell
        Selection.Columns(i).Cells(1, 1) = finalColumnText
    Next i

    ' Delete row 2
    Rows("2").Delete
End Sub

In MergeFirstTwoCellsInEachColumn2, the new column headings are simply written to the top cell and when this has been done for all columns, row two is deleted. This is perhaps the more elegant solution for most spreadsheets. A few comments on the code:

row1LastCol = Range("A1").currentRegion.End(xlToRight).Column

This line determines the last non-blank column in row 1. The currentRegion property of the Range object returns a "range bounded by any combination of blank rows and blank columns". When called on the Range("A1") object, it effectively selects the same region as Ctrl + End. It's then straightforward to inspect the End property and get the corresponding Column.

lastCol = WorksheetFunction.Max(row1LastCol, row2LastCol)

lastCol is the greater of the last columns in the first two rows (needed in case both rows don't have the same column number as the last column). This lastCol value is important because without it, Excel will chew lots of CPU running the macro on all the columns beyond those spanned by the input data.

2Jul/100

Where is the org.apache.bcel package located?

While reading through the JPF core source code (and other JPF extensions as well), you may come across classes like JavaClass, ClassParser, etc. These classes are part of the Byte Code Engineering Library and are in the org.apache.bcel package. In case you are interested in easily reading the corresponding source in your favorite editor (Eclipse in my case), download the appropriate source from the BCEL download page.

Filed under: JPF No Comments
1Jul/103

Installing and Running Java Path Finder (JPF)

The NASA AMES site has the necessary documentation for this procedure (and all else JPF). Nonetheless, I'm documenting the process here to save me some time the next time I need to do this since all commands will be in one spot.

For this project, I was running a Windows 7 box but these instructions should be easy to port to Linux other platforms. You will need to install the latest version of the Java Runtime Environment (JRE) and the Java Development Kit (JDK). Without the JDK installed (and included in your PATH environment variable), you will get the famous "javac is not recognized as an internal or external command." These tools can be found on Sun's website. Proceed to the command line and verify that these commands list the most up to date recent Java version available (JDK 6 Update 20 as of this posting).

javac -version
java -version

You will also need Mercurial to install JPF. For windows users, it may be easier to install TortoiseHg since it will automatically add the hg command to the PATH [needs confirmation]. On my system, I installed the JPF core into a JPF folder I created in my home folder. To do so, drop to the command line then:

cd %HOMEPATH%
mkdir jpf
cd jpf
hg clone http://babelfish.arc.nasa.gov/hg/jpf/jpf-core

To build the source and run the test suite:

cd jpf-core
bin/ant test

This ant script requires the JAVA_HOME environment variable to be set (on Windows anyway). I set it to my JDK installation path.

Note: for my initial checkout, I cloned http://babelfish.arc.nasa.gov/hg/jpf but expecting to get the whole tree, but the subrepositories were empty! All the extensions must be separately cloned. Before running the Racer example mentioned on the JPF page, you need to set up the site.properties file. This file should be placed in a folder called ".jpf" in the user's home directory. Attempting to run the example before setting up this file will give you the error message: "gov.nasa.jpf.JPFClassLoaderException: no classpath entry for gov.nasa.jpf.JPF found (check site.properties)".

cd %HOMEPATH%
mkdir .jpf
cd .jpf

echo # JPF site configuration > site.properties
echo # >> site.properties
echo jpf-core = ${user.home}/jpf/jpf-core >> site.properties
echo # >> site.properties
echo # numeric extension >> site.properties
echo jpf-numeric = ${user.home}/jpf/jpf-numeric >> site.properties
echo extensions+=${jpf-numeric} >> site.properties
echo # >> site.properties
echo # annotation-based program properties extension >> site.properties
echo jpf-aprop = ${user.home}/jpf/jpf-aprop >> site.properties
echo extensions+=,${jpf-aprop} >> site.properties
echo # >> site.properties
echo #... and all your other installed projects >> site.properties
echo # >> site.properties

Verify that site.properties has been successfully created. Now we can run the example:

java -jar build/RunJPF.jar src/examples/Racer.jpf

Et voila! You should now see output like:

JavaPathfinder v5.0 - (C) 1999-2007 RIACS/NASA Ames Research Center

====================================================== system under test
application: Racer.java

====================================================== search started: 7/1/10 5:51 PM
10
10

====================================================== error #1
gov.nasa.jpf.listener.PreciseRaceDetector
race for: "int Racer.d"
  main at Racer.main(Racer.java:16)
                "int c = 420 / racer.d;               // (4)"  : getfield
  Thread-0 at Racer.run(Racer.java:7)
                "d = 0;                               // (2)"  : putfield

====================================================== snapshot #1
thread index=0,name=main,status=RUNNING,this=java.lang.Thread@0,target=null,priority=5,lockCount=0,suspendCount=0
  call stack:
        at Racer.main(Racer.java:16)

thread index=1,name=Thread-0,status=RUNNING,this=java.lang.Thread@272,target=Racer@271,priority=5,lockCount=0,suspendCount=0
  call stack:
        at Racer.run(Racer.java:7)

====================================================== results
error #1: gov.nasa.jpf.listener.PreciseRaceDetector "race for: "int Racer.d"    main at Racer.main(Race..."

====================================================== statistics
elapsed time:       0:00:00
states:             new=9, visited=1, backtracked=4, end=2
search:             maxDepth=5, constraints=0
choice generators:  thread=8, data=0
heap:               gc=8, new=278, free=32
instructions:       2956
max memory:         15MB
loaded code:        classes=68, methods=988

====================================================== search finished: 7/1/10 5:51 PM
Filed under: JPF 3 Comments