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round result of floating point calcualtion

Hello,

I have a problem with the accuracy of the result when I divide 2 float values.

This is the line in my source Code:

 dds_word.long_dds = 2.147483648E16 / 7.1312E7

The result which I get is 3.011392E8

The unrounded result is 3.0113916845E8

There is no difference when I work with float or double variables. Is there any possibility to get more accuracy?

Parents

0 Jan Hauschildt over 21 years ago in reply to Graham Cole

I have solved the problem.
Here is the solution which I use. I hope I will get no problem with the timing.


unsigned long test_value;
unsigned int result;
unsigned long test_freq;


         dds_word.long_dds = 0;
         test_value = 0x04C4B400;
         for (i=0; i<7; i++)
            {
            result = test_value / test_freq;
            test_value = test_value - (result * test_freq);
            test_value = test_value << 4;
            dds_word.long_dds += result;
            dds_word.long_dds = dds_word.long_dds << 4;
            }
         result = test_value / test_freq;
         dds_word.long_dds += result;

Thx at all for help.

Jan

Reply

0 Jan Hauschildt over 21 years ago in reply to Graham Cole

I have solved the problem.
Here is the solution which I use. I hope I will get no problem with the timing.


unsigned long test_value;
unsigned int result;
unsigned long test_freq;


         dds_word.long_dds = 0;
         test_value = 0x04C4B400;
         for (i=0; i<7; i++)
            {
            result = test_value / test_freq;
            test_value = test_value - (result * test_freq);
            test_value = test_value << 4;
            dds_word.long_dds += result;
            dds_word.long_dds = dds_word.long_dds << 4;
            }
         result = test_value / test_freq;
         dds_word.long_dds += result;

Thx at all for help.

Jan

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