Wrong Decimal Calculations

RE: Wrong Decimal Calculations

Puspendu Pal — Thu, 26 Oct 2017 18:41:08 GMT

Agreed with James,

In our project, we used combination of fixed() and round() functions to over come this issue.

RE: Wrong Decimal Calculations

James — Thu, 26 Oct 2017 13:04:24 GMT

Hi @Vaibhav,

This looks likely to be a rounding error due to Floating Point Arithmetic. I believe Appian uses the Java Primitive double for Number(decimal) under the hood, which is a 64-bit IEEE 754 floating point. IEEE 754 is the technical standard for floating-point computation, this is the most widely used standard for floating point arithmetic and number formats.

The issue is that some numbers have an infinite number of digits, and can not be represented with 100% precision with only 64-bits. But it's not just Pi that can be affected by this, something as simple as 1/10, or 0.1 can be affected.

For instance, the below code would print false to the console in Java:

double x1 = 0.3;

double x2 = 0.1 + 0.1 + 0.1;

StdOut.println(x1 == x2);

However, the below code would print true:

double z1 = 0.5;

double z2 = 0.1 + 0.1 + 0.1 + 0.1 + 0.1;

StdOut.println(z1 == z2);

This is just a limitation of the IEEE 754 standard, and there's few ways to get around it. To do so purely in Appian will require some rouding work around, or similiar, as suggest by @manikandanp13

Financial Java applications often use the BigDecimal Class, which provides more precision through larger storage of numbers and more robust mathematical functions. You could consider building a plugin that would allow access to the BigDecimal Class and it's functionality. I did a quick search on shared components and found https://forum.appian.com/suite/tempo/records/item/lMBCLGOdlMUpdGVqW3dQaIKmclBmvvNEj8vu_cjb7T-5YiPr4Fu8ly5Yj1s09uenE4RYzA8zKyx7eiUhe2kLnO1l8v4PFM9U_yr4yMcNagKDuviUQ/view/summary

Some additional reading that goes more into the Rounding issue of Floating Point Arithmetic:

https://docs.oracle.com/cd/E19957-01/806-3568/ncg_goldberg.html

https://introcs.cs.princeton.edu/java/91float/

Best Regards

RE: Wrong Decimal Calculations

manikandanp13 — Thu, 26 Oct 2017 02:15:13 GMT

absolutely; This calculation produce 92000 - (7000.27 + 73000.27 + 2000.33 + 9999.13) => -1.455192e-011 i.e. - 0.00000000001455192
Please refer results when use round function.
= round ((92000 - (7000.27 + 73000.27 + 2000.33 + 9999.13)),0) => -0
= round ((92000 - (7000.27 + 73000.27 + 2000.33 + 9999.13)),20) => -1.455192e-011
= round ((92000 - (7000.27 + 73000.27 + 2000.33 + 9999.12)),0) => 0
= round ((92000 - (7000.27 + 73000.27 + 2000.33 + 9999.12)),20) => 0.01

not sure have use some mathematical functions as best practices when do mathematical operations

RE: Wrong Decimal Calculations

aloks0189 — Wed, 25 Oct 2017 22:22:34 GMT

Hi Vaibhav Tandale It's really weird, i believe it's better you raise a support ticket to Product Team, because it's normal calculation and it should work.