A collection of coding snippets, tips, hints and random thoughts.
It is more mature and feature-rich, compared to gitx. But it is closed source. However, it is free (as in beer) for the time being in the App Store. So far, the program seems really nice. Let’s see how long I will continue using it, and if I’ll go back to gitx at some point.
XCode 4 has always been incredibly slow for me. The first release, 4.0, was especially bad. But that was just a .0 version. The next release 4.1 is much better, but it has also severe drawbacks, concerning performance. Everytime I start it, and not even do much with it, my system gets incredibly slow. That is on both a C2D 2.8 GHz MBP and also on a quad-core i7 MBP. Both machines come with 4 GB of RAM, and after firing XCode up and loading a large project, still at least 500 MB of it remains free. However, speed is abysmal. I just found the tool vmmap in OS X, and it gives me this output:
==== Summary for process 32136
ReadOnly portion of Libraries: Total=265.8M resident=114.4M(43%) swapped_out_or_unallocated=151.5M(57%)
Writable regions: Total=16.2G written=149.6M(1%) resident=360.9M(2%) swapped_out=6156K(0%) unallocated=15.9G(98%)
REGION TYPE VIRTUAL
=========== =======
CG backing stores 19.4M
CG image 268K
CG raster data 2840K
CG shared images 3472K
CoreAnimation 180K
CoreGraphics 16K
CoreImage 108K
CoreServices 1704K
IOKit 61.2M
MALLOC 337.4M see MALLOC ZONE table below
MALLOC (reserved) 15.6G reserved VM address space (unallocated)
MALLOC freed, no zone 30.5M
MALLOC guard page 64K
MALLOC metadata 128.8M
Memory tag=240 4K
Memory tag=242 12K
Memory tag=243 4K
Memory tag=249 156K
Memory tag=251 64K
OpenCL 60K
OpenGL GLSL 1372K
OpenGL GLSL (reserved) 128K reserved VM address space (unallocated)
SQLite page cache 14.6M
STACK GUARD 56.1M
Stack 19.7M
VM_ALLOCATE 16.1M
__CI_BITMAP 80K
__DATA 33.9M
__IMAGE 1256K
__LINKEDIT 59.5M
__TEXT 206.4M
__UNICODE 544K
mapped file 72.9M
shared memory 13.6M
=========== =======
TOTAL 16.7G
TOTAL, minus reserved VM space 1.1G
So the virtual memory space that XCode takes is more than 16 GB! The actual memory taken is “only” 1.1 GB, which is still huge, but my Emacs also takes 500 MB with tons of C++, Python and LaTeX buffers open.
The question is: can the unallocated, but reserved 16 GB address space degrade the performance? I have too little knowledge of the workings of virtual memory on Intel CPUs under OS X. But this value seems incredibly huge.
Update: I have asked a question on Stackoverflow, and have gotten some useful answers. What did help was removing my build/ folder from the git. Accidentally, a colleague checked in four files in the build/ folder. This made Xcode very slow, since it was checking the git status during compilation all the time. Still, Xcode 4 is much slower than Xcode 3 after this. So I also upgraded our machines to have at least 8 GB of RAM. This was definitely much of an improvement. It seems that development machines using Xcode 4 should have 8 GB RAM minimum. The more, the better…
I am currently writing a lot of text in Emacs, and I need to work on multiple files in parallel. So I use the split window functionality a lot. With C-x o you can switch to the next split window. However, it would be nice to go backward as well. The solution is simple, and is given on Stackoverflow and some other blogs:
(defun prev-window ()
(interactive)
(other-window -1))
(global-set-key (kbd "C-x p") 'prev-window)
Just put this in you init.el, and you can cycle backwards using C-x p.
If you ever need to delete the “active” branch in a git repository, you need to first switch the active branch. Because you cannot delete the branch you are sitting on… You cannot checkout a branch, as you would usually do. You have to change the symbolic reference called HEAD. You can do this with the symbolic-ref command:
$ git branch
* deletethis
somebranch
$ git symbolic-ref HEAD refs/heads/somebranch
$ git branch
deletethis
* somebranch
$ git branch -d deletethis
There is a very useful utility called security(1) in OS X, which lets you manipulate your keychain from the command line. You can easily im- and export keys and certificates using this. This is especially useful for AppStore developers, who code on multiple Macs. Having the signing keys in sync is kind of a challenging solution, if you don’t use keychain syncing via MobileMe. For example you can import a key like this into your login keychain:
$ security list-keychains
"/Users/yourguy/Library/Keychains/login.keychain"
"/Library/Keychains/System.keychain"
$ security import -k /Users/yourguy/Library/Keychains/login.keychain somekey.pem
1 key imported.
Hope this helps.
As a reminder for myself, here is how you can codesign an OS X application for the AppStore on the command line:
codesign -f -s "3rd Party Mac Developer Application: Your Company" -v YourApp.app
productbuild --component YourApp.app /Applications --sign "3rd Party Mac Developer Installer: Your Company" YourApp.pkg
There is a lot more to do, of course, like having the correct bundle ID set, but this speeds up codesigning, if you do not use XCode to build your application.
For iOS it is pretty similar, except you don’t need the productbuild:
codesign -f -s "iPhone Distribution: Your Company" -v YourApp.app
I recently started using matplotlib together with PyQt, and I love it. It’s awesome and has many more features compared to PyQWT. However, I needed to save the plots to a PDF file. Here is how you do that:
import matplotlib.backends.backend_pdf
...
@QtCore.pyqtSlot()
def printPlots(self):
filename,_ = QtGui.QFileDialog.getSaveFileName(self, "Save plots as PDF file", "", "Portable Document File (*.pdf)")
if filename == "":
return
pp = matplotlib.backends.backend_pdf.PdfPages(filename)
pp.savefig(self.plotFigure)
pp.close()
Assuming that your figure is called self.plotFigure. You can connect the above slot to a QAction and map it to some nice menu item or shortcut.
I just had a funny thought. In Python you can write:
if not someObject is None:
someObject.doSomething()
else:
print "someObject is None!"
This reads a bit strange. So what if you could alias “not … is None” to “… is Something”?
if someObject is Something:
someObject.doSomething()
else:
print "someObject is None!"
>>> Something = not None
>>> Something
True
>>> A = [1,2,3]
>>> if A is Something:
... print "This is something"
... else:
... print "This is nothing"
...
This is nothing
>>>
Someone at Carbon Five posted a nice article about XCode 4 and using external dependencies. For XCode 3, I already know how to use direct dependencies and static libraries. The above article seems pretty well explained, though I have not yet tested it. I will try to give some feedback once I have the time to try it myself.