More price updates

data/global_stocks.csv

-plumCropItem,V1
-FruitVeg,182.092751337307
-WheatBarleyOats,879.537641313273
-Pulses,46.532195
-Starchy Roots,410.796684630225
-Oilcrops,378.961539547602
-MaizeMilletSorghum,810.753713560517
-Sugar,1484.01363920056
-Rice (Paddy Equivalent),439.184612481259
-Ruminants,412.1217514
-Monogastrics,45.6726812
+plumCropItem,V1
+FruitVeg,182.092751337307
+WheatBarleyOats,879.537641313273
+Pulses,46.532195
+Starchy Roots,410.796684630225
+Oilcrops,378.961539547602
+MaizeMilletSorghum,810.753713560517
+Sugar,1484.01363920056
+Rice (Paddy Equivalent),439.184612481259
+Ruminants,412.1217514
+Monogastrics,45.6726812
+Energy crops,20
\ No newline at end of file

src/ac/ed/lurg/InternationalMarket.java

@@ -69,7 +69,7 @@ public class InternationalMarket {
 			GlobalPrice prevPrice = worldPrices.get(crop);
 			double imports = totalImportCommodities.containsKey(crop) ? totalImportCommodities.get(crop) : 0.0;
 			double exportsBeforeTransportLosses = totalExportCommodities.containsKey(crop) ? totalExportCommodities.get(crop) : 0.0;
-			LogWriter.print(timestep.getYear() + " Updating " + crop.getGamsName() + " prices : ");
+			LogWriter.println(timestep.getYear() + " Updating " + crop.getGamsName() + " prices");
 			GlobalPrice adjustedPrice = prevPrice.createWithUpdatedMarketPrices(imports, exportsBeforeTransportLosses, timestep, totalProduction.get(crop));
 			LogWriter.println( String.format("Price for %s updated from %s to %s \n", crop.getGamsName(), prevPrice, adjustedPrice));
 			worldPrices.put(crop, adjustedPrice);

src/ac/ed/lurg/country/GlobalPrice.java

@@ -67,50 +67,47 @@ public class GlobalPrice {
 
 	public GlobalPrice createWithUpdatedMarketPrices(double newImports, double newExportAmountBeforeLoss, Timestep timestep, double production) {
 
-		double transportLossRate = (!ModelConfig.SHOCKS_POSSIBLE) ? ModelConfig.TRANSPORT_LOSSES : ModelConfig.getParameter(Parameter.TRANSPORT_LOSSES, timestep.getYear());
-		double newTransportLosses = newExportAmountBeforeLoss * transportLossRate;
-		double exportsAfterTransportLosses = newExportAmountBeforeLoss - newTransportLosses;
-		
-		if (newImports > 0 || exportsAfterTransportLosses > 0) {
-			double oldDiff = 0;
-			if (timestep.getTimestep() == timestepId)  // if recomputing for same year need to back our previous adjustment
-				oldDiff = exportAmountBeforeLoss - transportLosses - importAmount;
-			double newDiff = newExportAmountBeforeLoss - newTransportLosses - newImports;
-			double updatedStock = stockLevel + newDiff - oldDiff;
-			
-			LogWriter.println(String.format(" global stocks from %.2f to %.2f due to newDiff %.2f oldDiff %.2f", stockLevel, updatedStock, newDiff, oldDiff));
+		if (newImports > 0 || newExportAmountBeforeLoss > 0) {
+			double oldDiff = timestep.getTimestep() != timestepId ? 0.0 : exportAmountBeforeLoss - transportLosses - importAmount; // if recomputing for same year need to back our previous adjustment
+			double transportLossRate = (!ModelConfig.SHOCKS_POSSIBLE) ? ModelConfig.TRANSPORT_LOSSES : ModelConfig.getParameter(Parameter.TRANSPORT_LOSSES, timestep.getYear());
+			double newTransportLosses = newExportAmountBeforeLoss * transportLossRate;
+			double stockChange = newExportAmountBeforeLoss - newTransportLosses - newImports - oldDiff;
+			double updatedStock = stockLevel + stockChange;
+				
+			LogWriter.println(String.format("     imports %.2f, exports %.2f", newImports, newExportAmountBeforeLoss - newTransportLosses));
+			LogWriter.println(String.format("     updatedStock %.2f, previous %.2f (last timestep %.2f), stockChange %.2f, oldDiff %.2f", updatedStock, stockLevel, stockLevel-oldDiff, stockChange, oldDiff));
 			if (updatedStock < 0)
 				LogWriter.println(String.format("Global stocks are below zero"));
 			
-			double newPrice, adjustment;
+			double adjustment;
 			double financialSpeculationMultiplier = (!ModelConfig.SHOCKS_POSSIBLE)? 1.0 : ModelConfig.getParameter(Parameter.FINANCIAL_SPECULATION_MULTIPLIER,timestep.getYear());
 
 			if (!ModelConfig.MARKET_ADJ_PRICE) {
 				adjustment = 1;
 			}
 			else if (ModelConfig.PRICE_UPDATE_BY_MARKET_IMBALANCE) {
-				double ratio = (newImports-exportsAfterTransportLosses)/(newImports-exportsAfterTransportLosses+production);
-				adjustment =  Math.exp(ratio * ModelConfig.MARKET_LAMBA);
-				LogWriter.println(String.format("Price update market imbalance: adjustment= %.4f, imports %.1f, exports %.1f", adjustment, newImports, getExportsAfterTransportLosses()));
+				double ratio = stockChange/(production-stockChange);
+				adjustment =  Math.exp(-ratio * ModelConfig.MARKET_LAMBA);
+				LogWriter.println(String.format("     initally imbalance ratio= %.4f", ratio));
 			}
 			else {
-				double ratio = (stockTarget - updatedStock) / stockTarget;
-				
-				if (ratio >= 0) {
-					adjustment = 1 + ModelConfig.MARKET_LAMBA * ratio/(1 - ratio*ratio);
-					if (adjustment > ModelConfig.MAX_PRICE_INCREASE || ratio > 1)
-						adjustment = ModelConfig.MAX_PRICE_INCREASE;  // default to max up change
-				}
-				else {
-					adjustment = 1 / ( 1 - ModelConfig.MARKET_LAMBA * ratio/(1 - ratio*ratio));
-					if (adjustment < ModelConfig.MAX_PRICE_DECREASE  || ratio < -1)
-						adjustment = ModelConfig.MAX_PRICE_DECREASE;  // default to max down change
-				}
+				if (stockChange >= 0) // stock increasing, so decrease price.  stockChange is positive so adjustment < 1
+					adjustment = 1 - ModelConfig.MARKET_LAMBA * stockChange/production;
+				else // stock decreasing, so increase price.  stockChange is negative so adjustment > 1
+					adjustment = 1 - ModelConfig.MARKET_LAMBA * stockChange/Math.max(0, stockLevel);
 				
-				LogWriter.println(String.format("Price update from stock target: adjustment= %.4f, ratio= %.4f", adjustment, ratio));
+				LogWriter.print(String.format("     initally adjustment= %.4f", adjustment));
 			}
 			
-			newPrice = exportPrice * adjustment * financialSpeculationMultiplier;
+			if (adjustment < ModelConfig.MAX_PRICE_DECREASE)
+				adjustment = ModelConfig.MAX_PRICE_DECREASE;  // default to max down change
+
+			if (adjustment > ModelConfig.MAX_PRICE_INCREASE)
+				adjustment = ModelConfig.MAX_PRICE_INCREASE;  // default to max up change
+			
+			LogWriter.println(String.format(", after limit %.4f", adjustment));
+
+			double newPrice = exportPrice * adjustment * financialSpeculationMultiplier;
 			return new GlobalPrice(timestep.getTimestep(), newPrice, updatedStock, stockTarget, newImports, newExportAmountBeforeLoss, newTransportLosses);			
 		}
 		else {
@@ -127,5 +124,4 @@ public class GlobalPrice {
 	public double getStockChange() {
 		return exportAmountBeforeLoss - transportLosses - importAmount;
 	}
-}
-
+}
\ No newline at end of file