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Altera_Forum
Honored Contributor I
743 Views

Does logarithm megafunction do well??

Hello Sir, 

 

I am using ALTFP_LOG megafunction in my application, 

so when i verify this ip core, i get abnormal results for 

particular integer values. 

 

If i give particular inputs of few numbers to ALTFP_LOG, 

i was unable to get the accurate values to the given inputs. 

 

For example, i'm using counter as input data block to generate some values 

for the inputs of ALTFP_LOG megafunction, 

 

or say that i'm using ALTFP_CONVERT to convert Integer-to-Float from the  

counter due to input format of ALTFP_LOG megafunction. 

 

and for the input values respected output values are given below.. 

 

x - ln(x) 

 

1 - 0 

2 to 4 - 1 

5 to 12 - 2 

13 to 33- 3 

34 to 92- 4 

 

so on... 

 

but if we see the value of ln(92) = 4.5217885770490403096412170747265, 

but here we see 4 as output.. 

 

as we check for the value for some hundred's or thousand's number, 

 

the IP ALTFP_LOG megafunction output will not be correct. 

 

 

So i would like to know how accurate this IP core is? 

what i must do to get expected or accurate result.. 

 

Please kindly do the needful..
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Altera_Forum
Honored Contributor I
27 Views

Did you ever look at the float output numbers?