SDC: Fix approximate equality condition Signed-off-by: Tomasz Michalak <tmichalak@antmicro.com>

diff --git a/sdc-plugin/buffers.cc b/sdc-plugin/buffers.cc
index c997bfa..cb54743 100644
--- a/sdc-plugin/buffers.cc
+++ b/sdc-plugin/buffers.cc

@@ -35,13 +35,13 @@
 
 void Pll::CheckInputClockPeriod(RTLIL::Cell* cell, float input_clock_period) {
     float abs_diff = fabs(ClkinPeriod() - input_clock_period);
-    bool approx_equal = abs_diff < max(ClkinPeriod(), input_clock_period) * kApproxEqualFactor;
+    bool approx_equal = abs_diff < max(ClkinPeriod(), input_clock_period) * 10 * std::numeric_limits<float>::epsilon();
     if (!approx_equal) {
 	log_cmd_error(
-	    "CLKIN[1/2]_PERIOD isn't approximately equal (+/-%.2f%%) to the virtual clock constraint "
+	    "CLKIN[1/2]_PERIOD doesn't match the virtual clock constraint "
 	    "propagated to the CLKIN[1/2] input of the clock divider cell: "
 	    "%s.\nInput clock period: %f, CLKIN[1/2]_PERIOD: %f\n",
-	    kApproxEqualFactor * 100, RTLIL::id2cstr(cell->name), input_clock_period, ClkinPeriod());
+	    RTLIL::id2cstr(cell->name), input_clock_period, ClkinPeriod());
     }
 }
 

diff --git a/sdc-plugin/buffers.h b/sdc-plugin/buffers.h
index 72beb0b..5f51535 100644
--- a/sdc-plugin/buffers.h
+++ b/sdc-plugin/buffers.h

@@ -61,8 +61,7 @@
 
    private:
     // Approximate equality check of the input clock period and specified in
-    // CLKIN[1/2]_PERIOD parameter kApproxEqualFactor specifies the percentage
-    // of the maximum accepted difference
+    // CLKIN[1/2]_PERIOD parameter
     void CheckInputClockPeriod(RTLIL::Cell* cell, float input_clock_period);
 
     // Fetch cell's parameters needed for further calculations
@@ -83,8 +82,6 @@
     float divclk_divisor;
     float clk_mult;
     float clk_fbout_phase;
-    // Approximate equality factor of 1%
-    const float kApproxEqualFactor = 0.01;
 };
 
 #endif  // _BUFFERS_H_