"compare the results with benchmarks" and do what?
FLOPS means you need
1) FLOPs per some unit of work.
2) time for that unit of work.
Let's say you have some input file that does 1,000 iterations through some loop. The loop is a handy unit of work. It gets executed 1,000 times. It takes an hour.
The loop has some adds and multiplies and a few divides and a square root. You can count adds, multiplies and divides. You can count this in the source, looking for +, * and /. You can find the assembler-language output from the compiler, and count them there, too. You may get different numbers. Which one is right? Ask your boss.
You can count the square roots, but you don't know what it really does in terms of multiplies and adds. So, you'll have to do something like benchmark multiply vs. square root to get a sense of how long a square root takes.
Now you know the FLOPS in your loop. And you know the time to run it 1,000 times. You know FLOPS per second.
Then you look at LINPACK and find you're slower. Now what? Your program isn't LINPACK, and it's slower than LINPACK. Odds are really good that your code will be slower. Unless your code was written and optimized over the same number of years a LINPACK, you'll be slower.
Here's the other part. Your processor has some defined FLOPS rating against various benchmarks. Your algorithm is not one of those benchmarks, so you fall short of the benchmarks. Is this bad? Or is this the obvious consequence of not being a benchmark?
What's the actionable outcome going to be?
Measurement against some benchmark code base is only going to tell you that you're algorithm isn't the benchmark algorithm. It's a foregone conclusion that you'll be different; usually slower.
Obviously, the result of measuring against LINPACK will be (a) you're different and therefore (b) you need to optimize.
Measurement is only really valuable when done against yourself. Not some hypothetical instruction mix, but your own instruction mix. Measure your own performance. Make a change. See if your performance -- compared with yourself -- get better or worse.
FLOPS don't matter. What matters is time per unit of work. You'll never match the design parameters of your hardware because you're not running the benchmark that your hardware designers expected.
LINPACK doesn't matter. What matters is your code base and the changes you're making to change performance.