Add flag to start running the homotopy path ...

... in negative direction first.

Belonging to [master]:
  - #2040

SimulationRuntime/c/simulation/solver/nonlinearSolverHomotopy.c

@@ -42,6 +42,7 @@
 #include <stdlib.h>
 #include <string.h> /* memcpy */
 
+#include "simulation/options.h"
 #include "simulation/simulation_info_json.h"
 #include "util/omc_error.h"
 #include "util/varinfo.h"
@@ -2250,15 +2251,15 @@ int solveHomotopy(DATA *data, threadData_t *threadData, int sysNumber)
       if (runHomotopy == 1) {
         solverData->h_function = wrapper_fvec;
         solverData->hJac_dh = wrapper_fvec_der;
-        solverData->startDirection = 1.0;
+        solverData->startDirection = omc_flag[FLAG_HOMOTOPY_NEG_START_DIR] ? -1.0 : 1.0;
         debugInt(LOG_INIT, "Homotopy run: ", runHomotopy);
         debugDouble(LOG_INIT,"startDirection = ", solverData->startDirection);
       }
 
       if (runHomotopy == 2) {
         solverData->h_function = wrapper_fvec;
         solverData->hJac_dh = wrapper_fvec_der;
-        solverData->startDirection = -1.0;
+        solverData->startDirection = omc_flag[FLAG_HOMOTOPY_NEG_START_DIR] ? 1.0 : -1.0;
         debugInt(LOG_INIT, "Homotopy run: ", runHomotopy);
         debugDouble(LOG_INIT,"Try again with startDirection = ", solverData->startDirection);
       }

SimulationRuntime/c/util/simulation_options.c

@@ -52,6 +52,7 @@ const char *FLAG_NAME[FLAG_MAX+1] = {
   /* FLAG_HOMOTOPY_MAX_LAMBDA_STEPS */    "homMaxLambdaSteps",
   /* FLAG_HOMOTOPY_MAX_NEWTON_STEPS */    "homMaxNewtonSteps",
   /* FLAG_HOMOTOPY_MAX_TRIES */           "homMaxTries",
+  /* FLAG_HOMOTOPY_NEG_START_DIR */       "homNegStartDir",
   /* FLAG_HOMOTOPY_ON_FIRST_TRY */        "homotopyOnFirstTry",
   /* FLAG_HOMOTOPY_TAU_DEC_FACTOR */      "homTauDecFac",
   /* FLAG_HOMOTOPY_TAU_DEC_FACTOR_PRED */ "homTauDecFacPredictor",
@@ -160,6 +161,7 @@ const char *FLAG_DESC[FLAG_MAX+1] = {
   /* FLAG_HOMOTOPY_MAX_LAMBDA_STEPS */    "[int (default size dependent)] maximum lambda steps allowed to run the homotopy path",
   /* FLAG_HOMOTOPY_MAX_NEWTON_STEPS */    "[int (default 20)] maximum newton steps in the homotopy corrector step",
   /* FLAG_HOMOTOPY_MAX_TRIES */           "[int (default 10)] maximum number of tries for one homotopy lambda step",
+  /* FLAG_HOMOTOPY_NEG_START_DIR */       "start to run along the homotopy path in the negative direction",
   /* FLAG_HOMOTOPY_ON_FIRST_TRY */        "directly use the homotopy method to solve the initialization problem",
   /* FLAG_HOMOTOPY_TAU_DEC_FACTOR */      "[double (default 10.0)] decrease homotopy step size tau by this factor if tau is too big in the homotopy corrector step",
   /* FLAG_HOMOTOPY_TAU_DEC_FACTOR_PRED */ "[double (default 2.0)] decrease homotopy step size tau by this factor if tau is too big in the homotopy predictor step",
@@ -294,6 +296,8 @@ const char *FLAG_DETAILED_DESC[FLAG_MAX+1] = {
   "  maximum newton steps in the homotopy corrector step",
   /* FLAG_HOMOTOPY_MAX_TRIES */
   "  maximum number of tries for one homotopy lambda step",
+  /* FLAG_HOMOTOPY_NEG_START_DIR */
+  "  start to run along the homotopy path in the negative direction",
   /* FLAG_HOMOTOPY_ON_FIRST_TRY */
   "  If the model contains the homotopy operator, directly use the homotopy method to solve the initialization problem.\n"
   "  Without this flag, the solver first tries to solve the initialization problem without homotopy and only uses homotopy as fallback option.",
@@ -540,6 +544,7 @@ const int FLAG_TYPE[FLAG_MAX] = {
   /* FLAG_HOMOTOPY_MAX_LAMBDA_STEPS */    FLAG_TYPE_OPTION,
   /* FLAG_HOMOTOPY_MAX_NEWTON_STEPS */    FLAG_TYPE_OPTION,
   /* FLAG_HOMOTOPY_MAX_TRIES */           FLAG_TYPE_OPTION,
+  /* FLAG_HOMOTOPY_NEG_START_DIR */       FLAG_TYPE_FLAG,
   /* FLAG_HOMOTOPY_ON_FIRST_TRY */        FLAG_TYPE_FLAG,
   /* FLAG_HOMOTOPY_TAU_DEC_FACTOR */      FLAG_TYPE_OPTION,
   /* FLAG_HOMOTOPY_TAU_DEC_FACTOR_PRED */ FLAG_TYPE_OPTION,

SimulationRuntime/c/util/simulation_options.h

@@ -60,6 +60,7 @@ enum _FLAG
   FLAG_HOMOTOPY_MAX_LAMBDA_STEPS,
   FLAG_HOMOTOPY_MAX_NEWTON_STEPS,
   FLAG_HOMOTOPY_MAX_TRIES,
+  FLAG_HOMOTOPY_NEG_START_DIR,
   FLAG_HOMOTOPY_ON_FIRST_TRY,
   FLAG_HOMOTOPY_TAU_DEC_FACTOR,
   FLAG_HOMOTOPY_TAU_DEC_FACTOR_PRED,