ss fixed

LLNL · Oct 1, 2024 · 78355ea · 78355ea
1 parent 60288dd
commit 78355ea
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Showing 3 changed files with 33 additions and 45 deletions.
diff --git a/examples/arkode/C_serial/ark_analytic_lsrk.out b/examples/arkode/C_serial/ark_analytic_lsrk.out
@@ -19,24 +19,24 @@ Analytical ODE test problem:
    ---------------------
 
 Final Statistics:
-Current time                 = 10.00665828381666
-Steps                        = 1674
-Step attempts                = 1683
+Current time                 = 10.01502208413611
+Steps                        = 1655
+Step attempts                = 1899
 Stability limited steps      = 0
-Accuracy limited steps       = 1682
-Error test fails             = 8
+Accuracy limited steps       = 1657
+Error test fails             = 2
 NLS step fails               = 0
 Inequality constraint fails  = 0
 Initial step size            = 1.930101110942615e-10
-Last step size               = 0.01925923265882638
-Current step size            = 0.01925923265882638
-RHS fn evals                 = 170959
+Last step size               = 0.019701
+Current step size            = 0.019701
+RHS fn evals                 = 168573
 RHS fn evals for Dom. Eigs.  = 0
 Number of dom_eig updates    = 1
-Avr. num. of stages taken    = 101.58
-Max. num. of stages taken    = 197
+Avr. num. of stages taken    = 88.77
+Max. num. of stages taken    = 199
 Max. num. of stages allowed  = 200
 Max. spectral radius         = 1010000.00
 Min. spectral radius         = 1010000.00
 
-ACCURACY at the final time = 1.01918e-13
+ACCURACY at the final time   = 1.18794e-13
diff --git a/examples/arkode/C_serial/ark_analytic_ssprk.out b/examples/arkode/C_serial/ark_analytic_ssprk.out
@@ -19,18 +19,18 @@ Analytical ODE test problem:
    ---------------------
 
 Final Statistics:
-Current time                 = 10.02392134053359
-Steps                        = 1116
-Step attempts                = 1119
+Current time                 = 10.02454272679074
+Steps                        = 1113
+Step attempts                = 1114
 Stability limited steps      = 0
-Accuracy limited steps       = 1119
-Error test fails             = 3
+Accuracy limited steps       = 1114
+Error test fails             = 1
 NLS step fails               = 0
 Inequality constraint fails  = 0
 Initial step size            = 1.930101110942615e-10
-Last step size               = 0.0257563455221273
-Current step size            = 0.0257563455221273
-RHS fn evals                 = 10071
+Last step size               = 0.02575789911873572
+Current step size            = 0.02575789911873572
+RHS fn evals                 = 10028
 Current stages taken         = 9
 
-ACCURACY at the final time = 2.35984e-09
+ACCURACY at the final time = 2.3602e-09
diff --git a/src/arkode/arkode_lsrkstep.c b/src/arkode/arkode_lsrkstep.c
@@ -983,34 +983,22 @@ int lsrkStep_TakeStepRKL(ARKodeMem ark_mem, sunrealtype* dsmPtr, int* nflagPtr)
     if (retval != ARK_SUCCESS) { return (retval); }
   }
 
-  /* determine the number of required stages */
-  /* Start by finding an ss value which is for sure less than the next req_stages 
-  and still large enough to reduce the number of for iterations*/
-  int ss = SUNRfloor(
-    SUNRsqrt(TWO * SUNRabs(ark_mem->h) * step_mem->sprad + THREE) - ONE);
-  /* Increase ss values by 1 each time to find the least feasible req_stages */
-  for (; ss <= step_mem->stage_max_limit; ss++)
-  {
-    if ((SUNSQR(ss) + ss - TWO) >= TWO * (SUNRabs(ark_mem->h) * step_mem->sprad))
+  int ss = SUNRceil((SUNRsqrt(SUN_RCONST(9.0) + SUN_RCONST(8.0) * SUNRabs(ark_mem->h) * step_mem->sprad) - ONE) / TWO);
+  step_mem->req_stages = SUNMAX(2, ss);
+  if (ss >= step_mem->stage_max_limit)
+  {
+    if (!ark_mem->fixedstep)
     {
-      step_mem->req_stages = SUNMAX(ss, 2);
-      break;
+      hmax = ark_mem->hadapt_mem->safety * (SUNSQR(ss) + ss - TWO) / (TWO * step_mem->sprad);
+      ark_mem->eta = hmax / ark_mem->h;
+      *nflagPtr    = ARK_RETRY_STEP;
+      return (ARK_RETRY_STEP);
     }
-    if (ss >= step_mem->stage_max_limit)
+    else
     {
-      if (!ark_mem->fixedstep)
-      {
-        hmax = ark_mem->hadapt_mem->safety * (SUNSQR(ss) + ss - TWO) / (TWO * step_mem->sprad);
-        ark_mem->eta = hmax / ark_mem->h;
-        *nflagPtr    = ARK_RETRY_STEP;
-        return (ARK_RETRY_STEP); 
-      }
-      else
-      {
-        arkProcessError(ark_mem, ARK_STEP_FIXED_SIZE_FAIL, __LINE__, __func__, __FILE__,
-                "Unable to achieve stable results: Either reduce the step size or increase the stage_max_limit");
-        return (ARK_STEP_FIXED_SIZE_FAIL);
-      }
+      arkProcessError(ark_mem, ARK_STEP_FIXED_SIZE_FAIL, __LINE__, __func__, __FILE__,
+              "Unable to achieve stable results: Either reduce the step size or increase the stage_max_limit");
+      return (ARK_STEP_FIXED_SIZE_FAIL);
     }
   }