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size_fact API shows different project values from Web Site
Hi,
I am working on one report to use Open HUB API to get man-month values of freeware component, i.e. https://github.com/blackducksoftware/ohloh_api/blob/master/reference/size_fact.md .
For Linux Kernel, the latest man-month value is shown as 12,625.
However, the website (https://www.openhub.net/p/3141/estimated_cost ) shows 5,876 person-years which is equal to 70,512 man-months.
May I know the reason that they have so big differences and how to get the correct value from API?
Thank you.
Hulei
Hi Hulei;
The estimated cost is based upon the COCOMO model, which is a formula for projecting a cost for a project based upon Effort Applied (man months), Development Time, and People Required.
The Size Fact is calculated by summing the number of man-months assigned by walking the project history. This is a completely different approach from COCOMO and has different inaccuracies, such as the fact that a full month is counted even if only one commit was made within a month.
Given the challenges with COCOMO, and that we use only the Basic Model, I would recommend using the Size Fact data since that is based upon actual commit activity.
Hi Peter,
Thank you for the reply. It helps us to understand the differences.
May I know if there is an API to get the estimated cost based upon the COCOMO model, if we want to have a report containing values shown in website?
Thanks,
Hulei
Hi Hulei;
We do not provide COCOMO values in our API, but you may be able to reproduce the value using coefficient values of a=2.4 and b=1.05. A post on our blog talks briefly about our use of COCOMO:
http://blog.openhub.net/project_codebase_cost/
Hi Peter,
This information is quite useful. Thanks a lot.
Best regards,
Hulei