Uploaded image for project: 'Embedded Software & Tools'
  1. Embedded Software & Tools
  2. EXT_EP-10056

Rounding error in floating point division of constant values

    XMLWordPrintable

Details

    • Bug
    • Status: Accepted
    • Low
    • Resolution: Unresolved

    Description

      The attached file contains this line ...

         if (delay  >= ( (unsigned short) (20e-3/(1e-3)) ) )

      Thus, you would expect the variable delay to be compared with the value 20.

      Build it ...

      % cl2000 -s try1.c

      Then inspect the resulting assembly file to see these lines ...

      ;----------------------------------------------------------------------
;   5 | if (delay  >= ( (unsigned short) (20e-3/(1e-3)) ) )
;----------------------------------------------------------------------
        MOVW      DP,#_delay            ; [CPU_ARAU]
        MOV       AL,@_delay            ; [CPU_ALU] |5|
        CMPB      AL,#19                ; [CPU_ALU] |5|
        B         $C$L1,LO              ; [CPU_ALU] |5|

      It is not compared again 20, but 19.

       

      Attachments

        Activity

          People

            syncuser TI User
            syncuser TI User
            Votes:
            0 Vote for this issue
            Watchers:
            2 Start watching this issue

            Dates

              Created:
              Updated: