DOSpad Math - on iPad 2

The Problem:  This whole effort has been driven by the math problems in DOSbox.  I fixed these on my first Blackberry Playbook version, and then later, on my Android gDOSbox stuff, and the GNUplot37 and APL's that I put up on the Google Play Store.  But DOSpad, the DOSbox inplementation on my hacked iPad has math problems.  I had to use a hacked/jailbroken iPad, since Apple iStore does *not* allow any programming languages or interpreters, and locks you into the "sandbox" where you cannot even save your own files to your own device.    The essense of the problem is shown in pic on screen right - the "Math Overflow Error" in a simple Fortran program that calculates sine using a Taylor series.  And it gets worse in GNUplot, with crazy number values appearing on the axis of graphs.

On the iPad1, running DOSpad, the math fails.  But running my repaired version (DOSpad Math) in an Xcode iPad device simulator, the same program calculates correctly.

Using Xcode to Deploy To a Real iPad 2

The Solution:   The solution here was to create a math-fixed version of DOSbox for the iPad that could actually be deployed to a real iPad.  This turns out to be a non-trivial project.  Something that should be a "./configure .. make .. make install" effort (10 minutes, maybe) on a Linux box, turns into a long, multi-day effort, with a few very late night search missions thru most of the IOS stuff on Stack Overflow.  After installing 4 different versions of Xcode (standardized on ver. 6.3.2, as I still am trying to get my new  "DOSpad Math" version of DOSbox onto by beloved iPad1).   But I have succeeded in getting a deployed version (using Xcode 7.1.1) to an iPad2, where I have confirmed the math routines run.  The picture at right, shows GNUplot37 running correctly in the Xcode Device Simulator.  Just getting the DOSpad fork, and the DOSbox stuff to compile under Xcode was an unbelievable amount of work, involving all-night head banging... Real "heavy metal" effort... Cool

And here is "DOSpad Math" running GNUplot37 on an iPad2. The massive amount of floating-point calcs required to draw a 3-D surface in GNUplot are a good test of an emulator's FPU (floating point unit) math processing capabilities. But I'm not sure if my developer credentials that code-signed the iPad's deployment will trigger what we used to call a "time-bomb", and stop the app from working in a week. Plus, I cannot migrate any GNUplot files, data-series, or workspaces until and unless I jailbreak the iPad2. But the proof-of-concept works. The iPad2 with it's little ARM chip, can be a powerful workstation you can slip in your pocket - if only Apple would be more sensible, and accommodate its developer community. They could allow FTP access to local storage, the way Android has always done. This would make the iPad vastly more useful. Apple might consider acting less like an abusive commandant of the IOS "jail", and more like a helpful concierge of a high-end hotel! Wouldn't that be a viable and profitable strategy? :)