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iSYSTEMTechBlog: Floating Point compare Precision adjustable

Since winIDEA build 9.11.69 the precision of floating point comparisons is adjustable.

When would that affect you? Well, every time you calculate with floating point numbers...

A floating point number is represented in a computer by several significant digits used for the number and an exponent, both in binary format. A definite dezimal number e.g. 0,1 can have an indefinite periodic binary representation e.g. 0,0001100110011. In a computer only the first digits of that periodic number are stored which may lead to inaccurateness in calculations, e.g.  will 10*0,1 in a computer result in 1,0? Well, it depends on the implementation...

Modern computers have additional to the main CPU (e.g. using 64 bits) a floating point unit (FPU e.g. using 80 bits). Assume you assign x=y=1; and compare cos(x) == cos(y); It can happen that this comparison is not true if cos(x) has been buffered (in memory 64 bit and therefore rounded) while cos(y) has been processed directly from the FPU (80 bit and was not rounded).

To solve this dilemma you can set the tolerable error due to rounding in floating point arithmetic - the so called machine epsilon. When you calculate the absolute error of a floating point comparison, it must be smaller or equal to epsilon (float x, y;): 
(x-y)<=epsilon

Since winIDEA build 9.11.69 you can now set the value for Floating point compare precision in menu Debug/ Debug Options/ Symbols.

iSYSTEMTechBlog: Profiler's professional Export Capabilities

winIDEA's profiler allows you to export your recorded data filtered by sophisticated patterns.

Beside you see the dialog for Profiler's Export.

After having specified a File name to export the data to, you set the export Format. Formats available are plain Text, XML, CSV and the so called Text1.
When you select Text1 format you can adjust the output format of many settings in the Options dialog (see screenshot below).

Scope defines the scope of data to export.
All Areas exports all areas.
Selection exports only areas currently selected in the profiler window.
Filter exports areas which match the specified filter wildcard pattern.
Only areas with recorded activity will be exported when "Export only active areas" is checked.

Time scope sets if the "entire session" or the selected range only  is exported.

In a multitasking environment specify the Context for which data is exported. This selection is only available if profiler session has recorded context switches.

In Information specify what type of data is exported. Statistics includes information like total time and percentage of time spent in the area, number of activations, etc. Timline exports time information e.g. for data time and value that was written and for functions time and state of activation. Data Object Mappings exports a mapping table for data objects e.g. task IDs.

Launch Associated Viewer tells the system to launch the viewer after export.

 

 

For detailed information on the Profiler export capabilities and examples see the Analyzer.pdf that is included in winIDEA's Technical Notes (Menu Help/ Technical Notes/ Analyzer.pdf).

iSYSTEMTechBlog: MPC5xxxx TLB write access Support

winIDEA supports since build 9.11.63 MPC5xxx TLB (Translation Lookaside Buffer) write access. TLB entries can now be written via MemoryWrite functions (included in isystem.connect API set).

To access a specific TLB entry, the access address encodes the TLB index in bits 16-31 and the MAS register (MMU Assist Registers) in bits 0-15.

The TLB manipulation functions are provided via isystem.connect's CMPC5xxxController class.

Example:
import isystem.connect as ic

cmgr = ic.ConnectionMgr()
cmgr.connectMRU('')

# get MPC5xxx controller
MPCCtrl = ic.CMPC5xxxController(cmgr)

# get TLB 3
TLB = MPCCtrl.getTLB(3)

# change RPN to 0x40800000 physical
TLB.m_dwMAS3 = 0x40800000 | (TLB.m_dwMAS3 & 0xFFF)

# set TLB 3
MPCCtrl.setTLB(3, TLB)

 

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