From 06a019a9709560e03de00eef9f9edc37511410ab Mon Sep 17 00:00:00 2001
From: Matthias Wachs <wachs@net.in.tum.de>
Date: Thu, 12 Jan 2012 16:27:58 +0000
Subject: - more mlp

---
 src/ats/gnunet-service-ats_addresses_mlp.c | 90 ++++++++++++++++++++++++++++++
 src/ats/gnunet-service-ats_addresses_mlp.h | 16 ++++++
 2 files changed, 106 insertions(+)

diff --git a/src/ats/gnunet-service-ats_addresses_mlp.c b/src/ats/gnunet-service-ats_addresses_mlp.c
index 734d07a13..946a2848d 100644
--- a/src/ats/gnunet-service-ats_addresses_mlp.c
+++ b/src/ats/gnunet-service-ats_addresses_mlp.c
@@ -38,6 +38,85 @@
 static struct GAS_MLP_Handle *GAS_mlp;
 
 
+/**
+ * Solves the MLP problem
+ * @return GNUNET_OK if could be solved, GNUNET_SYSERR on failure
+ */
+int
+mlp_solve_lp_problem (struct GAS_MLP_Handle *mlp)
+{
+  int res;
+
+  /* LP presolver?
+   * Presolver is required if the problem was modified and an existing
+   * valid basis is now invalid */
+  if (mlp->presolver_required == GNUNET_YES)
+    mlp->control_param_lp.presolve = GLP_ON;
+  else
+    mlp->control_param_lp.presolve = GLP_OFF;
+
+
+  /* Solve LP problem to have initial valid solution */
+lp_solv:
+  res = glp_simplex(mlp->prob, &mlp->control_param_lp);
+  if (res == 0)
+  {
+    /* The LP problem instance has been successfully solved. */
+  }
+  else if (res == GLP_EITLIM)
+  {
+    /* simplex iteration limit has been exceeded. */
+    // TODO Increase iteration limit?
+  }
+  else if (res == GLP_ETMLIM)
+  {
+    /* Time limit has been exceeded.  */
+    // TODO Increase time limit?
+  }
+  else
+  {
+    /* Problem was ill-defined, retry with presolver */
+    if (mlp->presolver_required == GNUNET_NO)
+    {
+      mlp->presolver_required = GNUNET_YES;
+      goto lp_solv;
+    }
+    else
+    {
+      /* Problem was ill-defined, no way to handle that */
+      GNUNET_log_from (GNUNET_ERROR_TYPE_ERROR,
+          "ats-mlp",
+          "Solving LP problem failed: glp_simplex error 0x%X", res);
+      return GNUNET_SYSERR;
+    }
+  }
+
+  /* Analyze problem status  */
+  res = glp_get_status (mlp->prob);
+  switch (res) {
+    /* solution is optimal */
+    case GLP_OPT:
+    /* solution is feasible */
+    case GLP_FEAS:
+      break;
+
+    /* Problem was ill-defined, no way to handle that */
+    default:
+      GNUNET_log_from (GNUNET_ERROR_TYPE_ERROR,
+          "ats-mlp",
+          "Solving LP problem failed, no solution: glp_get_status 0x%X", res);
+      return GNUNET_SYSERR;
+      break;
+  }
+
+  /* solved sucessfully, no presolver required next time */
+  mlp->presolver_required = GNUNET_NO;
+
+  return GNUNET_OK;
+}
+
+
+
 /**
  * Init the MLP problem solving component
  *
@@ -62,10 +141,21 @@ GAS_mlp_init (struct GNUNET_TIME_Relative max_duration, unsigned int max_iterati
 
   /* Init LP solving parameters */
   glp_init_smcp(&GAS_mlp->control_param_lp);
+#if DEBUG_MLP
+  GAS_mlp->control_param_lp.msg_lev = GLP_MSG_ALL;
+#else
+  GAS_mlp->control_param_lp.msg_lev = GLP_MSG_OFF;
+#endif
   GAS_mlp->control_param_lp.it_lim = max_iterations;
   GAS_mlp->control_param_lp.tm_lim = max_duration.rel_value;
+
   /* Init MLP solving parameters */
   glp_init_iocp(&GAS_mlp->control_param_mlp);
+#if DEBUG_MLP
+  GAS_mlp->control_param_mlp.msg_lev = GLP_MSG_ALL;
+#else
+  GAS_mlp->control_param_mlp.msg_lev = GLP_MSG_OFF;
+#endif
   GAS_mlp->control_param_mlp.tm_lim = max_duration.rel_value;
 
   return GNUNET_OK;
diff --git a/src/ats/gnunet-service-ats_addresses_mlp.h b/src/ats/gnunet-service-ats_addresses_mlp.h
index e57fb22bc..9272a2914 100644
--- a/src/ats/gnunet-service-ats_addresses_mlp.h
+++ b/src/ats/gnunet-service-ats_addresses_mlp.h
@@ -33,6 +33,8 @@
 #ifndef GNUNET_SERVICE_ATS_ADDRESSES_MLP_H
 #define GNUNET_SERVICE_ATS_ADDRESSES_MLP_H
 
+#define VERBOSE GNUNET_EXTRA_LOGGING
+#define DEBUG_MLP GNUNET_EXTRA_LOGGING
 
 #define MLP_MAX_EXEC_DURATION   GNUNET_TIME_relative_multiply(GNUNET_TIME_UNIT_SECONDS, 3)
 #define MLP_MAX_ITERATIONS      INT_MAX
@@ -68,6 +70,20 @@ struct GAS_MLP_Handle
    */
   unsigned int max_iterations;
 
+
+  /* state information */
+
+  /**
+   * Do we need to use the LP presolver?
+   *
+   * If the problem addresses were added or removed and the last basis was we
+   * need to use the presolver.
+   * presolver_required == GNUNET_YES
+   *
+   * If values were modified, we can reuse a valid basis
+   * presolver_required == GNUNET_NO
+   */
+  int presolver_required;
 };
 
 /**
-- 
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