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Rounding errors in vcd simulator time #560

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nturley opened this issue Dec 12, 2020 · 2 comments
Closed

Rounding errors in vcd simulator time #560

nturley opened this issue Dec 12, 2020 · 2 comments
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@nturley
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nturley commented Dec 12, 2020

As a consequence of #535, there's rounding errors in simulation time. I'm guessing this isn't a huge deal if your timescale is small enough and you are just plotting the result but I was trying to analyze simulation output and I was seeing the clock frequency move around a little bit during the simulation which was confusing.

To reproduce

I was working through the example here

sim = Simulator(dut)
sim.add_clock(1e-6) # 1 MHz

result

$comment Generated by nMigen $end
$date 2020-12-12 10:12:39.508725 $end
$timescale 100 ps $end
$scope module top $end
$var wire 1 0 ovf $end
$var wire 16 1 count $end
$var wire 1 2 clk $end
$var wire 1 3 rst $end
$var wire 1 4 en $end
$upscope $end
$enddefinitions $end
#0
$dumpvars
00
b0 1
02
03
04
$end
#5000
12
#10000
02
#15000
12
#20000
02
#24999
12
#29999
02
#34999
12
#40000
02
#45000
@whitequark
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whitequark commented Dec 12, 2020 •
edited

Isn't this issue just a duplicate of #535? The rounding errors are the exact problem that issue exists for.

@nturley
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nturley commented Dec 12, 2020

Fair enough.

@nturley nturley closed this as completed Dec 12, 2020
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@whitequark @nturley