Sample broken, Debug.Assert fails, RMW doesn't update output reference

[tskarman]

These two samples run into a failed assertion around Debug.Assert(output == value + 20);.

• https://github.com/microsoft/FASTER/blob/main/docs/_pages/home.md
• https://github.com/microsoft/FASTER/blob/main/docs/_docs/20-fasterkv-basics.md

While this sample that is not using the ref output signature of RMW but does a separate .Read() does not fail the assertion.

• https://github.com/microsoft/FASTER/blob/main/docs/_docs/01-quick-start-guide.md

From skimming the sample source it looked to me like the samples are using an implementation that is incomplete. But since the sample snippet from the docs doesn't actually use the sample source, there is prob. more going on so I'll leave the interpretation to you.

Blame links with line numbers to quickly jump to the respective samples:

Failing:

• https://github.com/microsoft/FASTER/blame/main/docs/_pages/home.md#L113
• https://github.com/microsoft/FASTER/blame/main/docs/_docs/20-fasterkv-basics.md#L388

Not failing:

• https://github.com/microsoft/FASTER/blame/main/docs/_docs/01-quick-start-guide.md#L53

[badrishc]

Good catch, the samples were assuming that the IFunctions implementation copies the new value to output, which SimpleFunctions did not. We have fixed SimpleFunctions to perform this copy to output. Note that you can always (recommended) write your own IFunctions implementation, extending from FunctionsBase or SimpleFunctions, for whatever behavior you desire. This commit fixes the issue for our in-built SimpleFunctions: 39af951 so that the samples work as they currently are.

[tskarman]

thank you! :-)