Databases
StackOverflow2013
Postsdbo
POStrange, float type parameter passing in function in windows
 

Note that there are some explanatory texts on larger screens.

plurals
  1. POStrange, float type parameter passing in function in windows
    primarykey
    data
    text
    <p>There is a piece of code confuse me, which runs in windows! Here is the code:</p> <pre><code>#define point_float2uint(x) *((unsigned int *)&amp;x) float divide_1000(float y) { float v = y / 1000.0f; return v; } float divide_1000(int y) { float v = float(y) / 1000.0f; return v; } void float_test(void) { int num[5] = {67975500, 67251500, 67540620, 69435500, 70171500}; for (int i = 0; i &lt; 5; ++i) { int a = num[i]; float af_f = divide_1000(float(a)); float af_i = divide_1000((a)); printf("src num:%d, af_f:%f, %x, af_i:%f, %x\n", num[i], af_f, point_float2uint(af_f), af_i, point_float2uint(af_i)); } } </code></pre> <p>Here is the output, compiled by vs2005:</p> <pre><code>src num:67975500, af_f:67975.507813, 4784c3c1, af_i:67975.500000, 4784c3c0 src num:67251500, af_f:67251.507813, 478359c1, af_i:67251.500000, 478359c0 src num:67540620, af_f:67540.625000, 4783ea50, af_i:67540.617188, 4783ea4f src num:69435500, af_f:69435.507813, 47879dc1, af_i:69435.500000, 47879dc0 src num:70171500, af_f:70171.507813, 47890dc1, af_i:70171.500000, 47890dc0 </code></pre> <p>The question is: why I use the "<strong>divide_1000</strong>", get the different result in windows? This is not what I want! And I find that not all the integer result in different, but some just like the code above. </p> <p>Here is the the output, comipled by gcc4.4.5 in debian:</p> <pre><code>src num:67975500, af_f:67975.507812, 4784c3c1, af_i:67975.507812, 4784c3c1 src num:67251500, af_f:67251.507812, 478359c1, af_i:67251.507812, 478359c1 src num:67540620, af_f:67540.625000, 4783ea50, af_i:67540.625000, 4783ea50 src num:69435500, af_f:69435.507812, 47879dc1, af_i:69435.507812, 47879dc1 src num:70171500, af_f:70171.507812, 47890dc1, af_i:70171.507812, 47890dc1 </code></pre> <p>I get the same result in useing different function "<strong>divide_1000</strong>". That's what I want.</p>
    singulars
    1. PO
      singulars
      1. PTAnswer
    1. This table or related slice is empty.
    1. PTQuestion
    1. UShdbean
    1. UShdbean
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. PO
      singulars
      1. PTAnswer
    1. VO
      singulars
      1. POStrange, float type parameter passing in function in windows
      1. This table or related slice is empty.
      1. VTUpMod
    2. VO
      singulars
      1. POStrange, float type parameter passing in function in windows
      1. USDRC
      1. VTFavorite
    1. COPlease read [What Every Computer Scientist Should Know About Floating-Point Arithmetic](http://docs.oracle.com/cd/E19957-01/806-3568/ncg_goldberg.html).
      singulars
      1. POStrange, float type parameter passing in function in windows
      1. USSome programmer dude
    2. CO@JoachimPileborg the question here maybe is for example why in other compilers the result is different, what kind of optimizations they are addressing differently from one another?
      singulars
      1. POStrange, float type parameter passing in function in windows
      1. USDRC
    3. CO@Joachim Pileborg Thank you for your help. But I think I know what's wrong with Floating-Point. Which confuse me is, why there are different results between first way and second way? Is there is an answer in "What Every Computer Scientist Should Know About Floating-Point Arithmetic"?
      singulars
      1. POStrange, float type parameter passing in function in windows
      1. UShdbean
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload