CSOWOPT Process
To access this process:
- Simulate ribbon >> Conditional Simulation >> Ore Waste.
- View the Find Command screen, select CSOWOPT and click Run.
- Enter "CSOWOPT" into the Command Line and press <ENTER>.
See this process in the Command Table.
Process Overview
Note: This is a superprocess and running it may have an effect on other Datamine files in the project.
This process identifies ore and waste blocks in a conditionally simulated model by minimizing the cost of incorrectly classifying ore as waste or waste as ore.
Reserves are calculated for a range of costs and prices for each cutoff, allowing the sensitivity of the reserves to changes in these parameters to be quantified.
The CSOWOPT process carries out the following functions:
- Inputs a conditionally simulated block model statistics file as created by CSMODEL.
- Inputs a range of processing costs and metal prices as defined by a minimum value, maximum value and increment. A single cost or price is selected by setting the minimum equal to the maximum.
- Calculates whether each block is ore or waste by minimizing the cost of misclassifying ore as waste or waste as ore for each combination of cost, price and cutoff.
- Creates a reserves table of tonnes and grade classified by cost, price and cutoff.
- Creates an output model identifying ore and waste blocks for each cutoff. This model is only created for the minimum cost and minimum price values
Input STATMOD Mode
This model must have been created as the output STATMOD model by the CSMODEL process. Details of the fields in this model are given in the description for CSMODEL. The fields used by the CSOWOPT process are;
- the 13 standard model fields (IJK, XC, XINC, NX, XMORIG, etc)
- MEAN: the mean grade for all realizations.
- PAx: the probability that the grade of the cell exceeds cutoff x.
- GAx: the grade of the cell above cutoff x.
- GBx: the grade of the cell below cutoff x.
Method
The decision as to whether a block is ore or waste is usually made by comparing the estimated grade of the block with a cutoff grade. There are four possible consequences of this decision:
- The true grade of the block is above cutoff and the block is sent to the mill
- The true grade of the block is above cutoff and the block is sent to the waste dump
- The true grade of the block is below cutoff and the block is sent to the waste dump
- The true grade of the block is below cutoff and the block is sent to the mill
The method used by CSOWOPT minimizes the cost of misclassifying ore and waste, cases 2 and 4 above. If the costs of mining ore and waste are equal, then the value of a block can be defined as:
Value = Revenue - Cost
where
Revenue = Mill Recovery (R) * Price (P) * Grade (G)
Cost = Cost of Mining and Milling (C)
So
Value = R*P*G - C
There are two types of value, potential and actual:
- The potential value of a block is the value of the block if the correct decision is made.
- The actual value of a block is the value of the block given the decision that was made.
The loss in value due to the decision is then the actual value minus the potential value. For cases 1 and 3 the actual and potential values are the same, so there is no loss due to the decision. However cases 2 and 4 give the following loses:
- Ore sent to waste dump: loss of potential value i.e. -(R*P*G - C)
- Waste sent to mill: actual difference between revenue and cost i.e. R*P*G - C
Since the grade G is actually a random variable, not a constant, there is a probability p that the grade is above cutoff. Therefore:
Total loss = (1-p) * (R*P*G - C) - p * (R*P*G - C)
This can be expressed as:
Expected loss = (1-p) * (R*P*GB - C) - p * (R*P*GA - C)
where GA is the grade above cutoff and GB the grade below cutoff.
A block is sent to the mill if the expected loss as a result of this decision is less than the expected loss from sending the block to the waste dump. The breakeven point occurs when the two loses are equal, which is when:
(1-p) * (R*P*GB - C) = - p * (R*P*GA - C)
Solving this for p gives:
p = (GB - C/(R*P)) / (GB - GA)
The probability that the block exceeds the cutoff grade is stored in field PAx in the input STATMOD model for cutoff x. The GA and GB values are also stored in the model as fields GAx and GBx respectively. Therefore by comparing the value of probability p with the value of PAx, the decision can be made as to whether the block should be classified as ore or waste:
- if PAx > p, then the block is classified as ore
- if PAx < p, then the block is classified as waste
Prices and Costs
Parameters COSTMIN, COSTMAX and COSTINC allow a range of processing costs to be specified. Cost includes both the mining and milling cost; it is assumed that mining cost is the same for ore and waste. Reserves are calculated for each cost COSTMIN, COSTMIN+1*COSTINC, COSTMIN+2*COSTINC, etc while the value is less than or equal to COSTMAX. If only a single cost is required then COSTMAX should be set equal to COSTMIN, or just left blank. Prices are specified in a similar way using parameters PRICEMIN, PRICEMAX and PRICEINC.
Care should be taken with the units in which costs and prices are specified. If the original grade units were in g/t then the fields GAx and GBx will also be in g/t. Then the cost should be in currency/t ( and the price should be in currency/g. If the grade units are % then prices should be multiplied by 0.01.
| Grade | Cost | Price | Price Multiplying Factor | Comment |
g/t | $/t | $/g | 1 |
|
| % | $/t | $/kg | 1/100 = 0.01 | Adjust for % |
| % | $/t | $/lb | 2204/100 = 22.04 | Adjust
for % and |
For example, if the metal price is 0.80 $/lb then the price value entered should by 0.80 * 22.04 = 17.632
Output OREMOD File
The output OREMOD file is a block model containing the 0/1 flags for each cutoff showing whether the cell is waste/ore for that cutoff. MEAN is the mean grade of the cell averaged over all realizations, and VARIANCE is the grade variance over all the realizations. Note that the model is only calculated for the minimum cost (COSTMIN) and minimum metal price (PRICEMIN). These two values are saved as implicit fields (not stored explicitly) in the model data definition. If you want to create the model for a cost and price value that are not the minimum, then you will need to rerun the process for just a single value of cost and price.
Field | Stored | Description |
IJK | Yes | IJK index |
XC | Yes | X coordinate of centre of parent cell |
YC | Yes | Y coordinate of centre of parent cell |
ZC | Yes | Z coordinate of centre of parent cell |
XINC | Yes | Parent cell size in the X direction |
YINC | Yes | Parent cell size in the Y direction |
ZINC | Yes | Parent cell size in the Z direction |
MEAN | Yes | Arithmetic mean grade |
VARIANCE | Yes | Variance |
OR0 | Yes | 0/1 flag showing waste/ore for cutoff 0 |
OR0.5 | Yes | 0/1 flag showing waste/ore for cutoff 0.5 |
.... | .... | .... |
OR9 | Yes | 0/1 flag showing waste/ore for cutoff 9 |
XINC | Yes | Parent cell size in the X direction |
YINC | Yes | Parent cell size in the Y direction |
ZINC | Yes | Parent cell size in the Z direction |
XMORIG | No | X origin of model |
YMORIG | No | Y origin of model |
ZMORIG | No | Z origin of model |
NX | No | Number of parent cells in the X direction |
NY | No | Number of parent cells in the Y direction |
NZ | No | Number of parent cells in the Z direction |
COST | No | Mining/milling cost (COSTMIN) |
PRICE | No | Metal price (PRICEMIN) |
Program Limits
Maximum number of costs = 30
Maximum number of prices = 30
System Files
_csolog.txt - Log file. Only useful if there is a problem.
_cso_*.txt - Temporary system files. These will be deleted if the process terminates cleanly.
_sp*.dm - Temporary Datamine files. These will be deleted if the process terminates cleanly.
All files matching the template _cso_*.txt and _sp*.dm are deleted as the process terminates. Therefore you should not use any of these file names for your own work.
Input Files
Name | Description | I/O Status | Required | Type |
STATMOD | Conditionally simulated block model statistics file. This file will have been created as the output STATMOD file by CSMODEL, and must include the fields PAx, GAx and GBx for at least one value of cutoff grade x. | Input | Yes | Block Model |
Output Files
Name | I/O Status | Required | Type | Description |
RESERVES | Output | Yes | Table | Output reserves file containing total tonnes and grade for blocks calculated as ore, classified by processing cost, metal price and cutoff. |
OREMOD | Output | No | Block Model | Output block model. This file includes flag field OWx which equals 1 if the block is ore and 0 if it is waste, for each cutoff x, for processing cost COSTMIN and metal price PRICEMIN . |
PLOT | Output | No | Plot | Template name for output plot file(s) showing tonnes, grade and/or metal above cutoff (Y axis) against cutoff (X axis). The PLOT file template name should be a maximum of 23 characters. A single character is added to this name to create the actual file name, as follows: G - Grade T - Tonnes M - Metal The parameters GPLOT , TPLOT and MPLOT define which plots to create. A minimum of 2 cutoffs must have been defined in order for the PLOT file(s) to be created. |
Example
!CSOWOPT
&STATMOD(statmod1),&RESERVES(reserve2),&OREMOD(oremod1),
@COSTMIN=30,@COSTMAX=40,@COSTINC=10,
@PRICEMIN=10,@PRICEMAX=12,@PRICEINC=2,
@RECOVERY=90,@DENSITY=2.5
Output Window
CSOWOPT
Initializing ....
Validating data ....
Accumulating reserves ....
Reserves for cost = 30 ....
Reserves for cost = 40 ....
The following files have been created:
reserve2: reserves above
cutoff file - 40 records
ocmodel: ore-waste model - 507 records
for
cost=30, price=10
Output RESERVES file
======================================================================
Filename c:\database\cond_sim\reserve2.dm
FILE CREATED BY SYSTEM USING SORTX ON
03/05/13
----------------------------------------------------------------------
FILE CONTAINS 40 RECORDS EACH
OF LENGTH 5
----------------------------------------------------------------------
FIELD TYPE WORD.NO STORED START DEFAULT
----------------------------------------------------------------------
COST N 1 Y 1 -
PRICE N 1 Y 2 -
CUTOFF N 1 Y 3 -
TONNES N 1 Y 4 -
GRADE N 1 Y 5 -
======================================================================
COST PRICE CUTOFF TONNES GRADE
======================================================================
30.0 10.0 0.0 1267500.0 5.52761
30.0 10.0 1.0 1267500.0 5.52761
30.0 10.0 2.0 1265000.0 5.53367
30.0 10.0 3.0 1240000.0 5.582169
30.0 10.0 4.0 1240000.0 5.582169
30.0 10.0 5.0 1167500.0 5.693158
30.0 10.0 6.0 1020000.0 5.857114
30.0 10.0 7.0 712500.0 6.196659
30.0 10.0 8.0 395000.0 6.587609
30.0 10.0 9.0 160000.0 6.992255
30.0 12.0 0.0 1267500.0 5.52761
30.0 12.0 1.0 1267500.0 5.52761
30.0 12.0 2.0 1265000.0 5.53367
30.0 12.0 3.0 1262500.0 5.539289
30.0 12.0 4.0 1247500.0 5.568272
30.0 12.0 5.0 1167500.0 5.693158
30.0 12.0 6.0 1020000.0 5.857114
30.0 12.0 7.0 712500.0 6.196659
30.0 12.0 8.0 395000.0 6.587609
30.0 12.0 9.0 160000.0 6.992255
40.0 10.0 0.0 1267500.0 5.52761
40.0 10.0 1.0 1267500.0 5.52761
40.0 10.0 2.0 1255000.0 5.547242
40.0 10.0 3.0 1147500.0 5.719683
40.0 10.0 4.0 1075000.0 5.825967
40.0 10.0 5.0 1075000.0 5.825967
40.0 10.0 6.0 990000.0 5.908365
40.0 10.0 7.0 712500.0 6.196659
40.0 10.0 8.0 395000.0 6.587609
40.0 10.0 9.0 160000.0 6.992255
40.0 12.0 0.0 1267500.0 5.52761
40.0 12.0 1.0 1267500.0 5.52761
40.0 12.0 2.0 1262500.0 5.537447
40.0 12.0 3.0 1212500.0 5.62963
40.0 12.0 4.0 1207500.0 5.63791
40.0 12.0 5.0 1165000.0 5.697874
40.0 12.0 6.0 1020000.0 5.857114
40.0 12.0 7.0 712500.0 6.196659
40.0 12.0 8.0 395000.0 6.587609
40.0 12.0 9.0 160000.0 6.992255
40 RECORDS LISTED
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