rearrange equation to reduce a number of divisions

Author: markelov208

applications/GeoMechanicsApplication/custom_utilities/constitutive_law_utilities.cpp

@@ -188,14 +188,15 @@ double ConstitutiveLawUtilities::CalculateK0NCFromFrictionAngleInRadians(double
 double ConstitutiveLawUtilities::UndrainedExcessPorePressureIncrement(const Properties& rProperties,
                                                                       double VolumetricStrainIncrement)
 {
-    const auto c_f              = 1.0 / rProperties[BULK_MODULUS_FLUID];
-    const auto c_s              = 1.0 / rProperties[BULK_MODULUS_SOLID];
-    const auto porosity         = rProperties[POROSITY];
-    const auto biot_coefficient = rProperties[BIOT_COEFFICIENT];
-    const auto denominator      = porosity * c_f + (biot_coefficient - porosity) * c_s;
-    KRATOS_ERROR_IF(abs(denominator) <= std::numeric_limits<double>::epsilon())
+    const double k_f              = rProperties[BULK_MODULUS_FLUID];
+    const double k_s              = rProperties[BULK_MODULUS_SOLID];
+    const double porosity         = rProperties[POROSITY];
+    const double biot_coefficient = rProperties[BIOT_COEFFICIENT];
+
+    const double denominator = porosity * k_s + (biot_coefficient - porosity) * k_f;
+    KRATOS_ERROR_IF(std::abs(denominator) <= std::numeric_limits<double>::epsilon())
         << "Non-physical values: denominator < epsilon." << std::endl;
-    return biot_coefficient / denominator * VolumetricStrainIncrement;
+    return biot_coefficient * (k_f * k_s) / denominator * VolumetricStrainIncrement;
 }
 
 } // namespace Kratos