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• How do I work out IEEE 754 64-bit Floating Point Double Precision?

  - by yousef gassar

  enter code herehello i have done it in 32 but i could dont do it in 62bits please i need help I am stuck on this question and need help. I don't know how to work it out. This is the question. Below are two numbers represented in IEEE 754 64-bit Floating Point Double Precision, the bias of the signed exponent is -1023. Any particular real number ‘N’ represented in 64-bit form (i.e. with the following bit fields; 1-bit Sign, 11-bit Exponent, 52-bit Fraction) can be expressed in the form ±1.F2 × 2X by substituting the bit-field values using formula (IV.I): N = (-1) S × 1.F2 × 2(E – 1023) for 0 < E < 2047.........................….(IV.I) Where N= the number represented, S=Sign bit-value, E=Exponent=X +1023, F=Fraction or Mantissa are the values in the 1, 11 and 52-bit fields respectively in the IEEE 754 64-bit FP representation. Using formula (IV.I), express the 64-bit FP representation of each number as: (i) A binary number of the form:- ±1.F2 × 2X (ii) A decimal number of the form:- ±0.F10 × 10Y {limit F10 to 10 decimal places} Sign 0 1 Exponent 1000 0001 001 11 Fraction 1111 0111 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 52 Sign 1 1 Exponent 1000 0000 000 11 Fraction 1001 0010 0001 1111 1011 0101 0100 0100 0100 0010 1101 0001 1000 52 I know I have to use the formula for each of the these but how do I work it out? Is it like this? N = (-1) S × 1.F2 × 2(E – 1023) = 1 x 1.1111 0111 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 0000 x 1000 0001 00111 (-1023)?

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• This is more a matlab/math brain teaser than a question

  - by gd047

  Here is the setup. No assumptions for the values I am using. n=2; % dimension of vectors x and (square) matrix P r=2; % number of x vectors and P matrices x1 = [3;5] x2 = [9;6] x = cat(2,x1,x2) P1 = [6,11;15,-1] P2 = [2,21;-2,3] P(:,1)=P1(:) P(:,2)=P2(:) modePr = [-.4;16] TransPr=[5.9,0.1;20.2,-4.8] pred_modePr = TransPr'*modePr MixPr = TransPr.*(modePr*(pred_modePr.^(-1))') x0 = x*MixPr Then it was time to apply the following formula to get myP , where µij is MixPr. I used this code to get it: myP=zeros(n*n,r); Ptables(:,:,1)=P1; Ptables(:,:,2)=P2; for j=1:r for i = 1:r; temp = MixPr(i,j)*(Ptables(:,:,i) + ... (x(:,i)-x0(:,j))*(x(:,i)-x0(:,j))'); myP(:,j)= myP(:,j) + temp(:); end end Some brilliant guy proposed this formula as another way to produce myP for j=1:r xk1=x(:,j); PP=xk1*xk1'; PP0(:,j)=PP(:); xk1=x0(:,j); PP=xk1*xk1'; PP1(:,j)=PP(:); end myP = (P+PP0)*MixPr-PP1 I tried to formulate the equality between the two methods and seems to be this one. To make things easier, I ignored from both methods the summation of matrix P. where the first part denotes the formula that I used, while the second comes from his code snippet. Do you think this is an obvious equality? If yes, ignore all the above and just try to explain why. I could only start from the LHS, and after some algebra I think I proved it equals to the RHS. However I can't see how did he (or she) think of it in the first place.

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• How to implement Excel Solver functionality in C#?

  - by Vic

  Hi, I have an application in C#, I need to do some optimization calculations, like Excel Solver Add-in does, one option is certainly to write my own solver implementation, but I'm kind of short of time, so I'm looking into libraries that already exist that can help me with this. I've been trying the Microsoft Solver Foundation, which seems pretty neat and cool, the problem is that it doesn't seem to work with the kind of calculations that I need to do. At the end of this question I'm adding the information about the calculations I need to perform and optimize. So basically my question is if any of you know of any other library that I can use for this purpose, or any tutorial that can help to do my own solver, or any idea that gives me a lead to solve this issue. Thanks. Additional Info: This is the data I need to calculate: I have 7 variables, lets call them var1, var2,...,var7 The constraints for these variables are: All of them need to be 0 <= varn <= 0.5 (where n is the number of the variable) The sum of all the variables should be equal to 1 The objective is to maximize the target formula, which in Excel looks like this: (MMULT(TRANSPOSE(L26:L32),M14:M20)) / (SQRT(MMULT(MMULT(TRANSPOSE(L26:L32),M4:S10),L26:L32))) The range that you see in this formula, L26:L32, is actually the range with the variables from above, var1, var2,..., varn. M14:M20 and M4:S10 are ranges with data that I get from different sources, there are more likely decimal values. As I said before, I was using Microsoft Solver Foundation, I modeled pretty much everything with it, I created functions that handle the operations of the target formula, but when I tried to solve the model it always fail, I think it is because of the complexity of the operations. In any case, I just wanted to show these data so you can have an idea about the kind of calculations that I need to implement.

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• Pass a range into a custom function from within a cell

  - by Luis

  Hi I'm using VBA in Excel and need to pass in the values from two ranges into a custom function from within a cell's formula. The function looks like this: Public Function multByElement(range1 As String, range2 As String) As Variant Dim arr1() As Variant, arr2() As Variant arr1 = Range(range1).value arr2 = Range(range2).value If UBound(arr1) = UBound(arr2) Then Dim arrayA() As Variant ReDim arrayA(LBound(arr1) To UBound(arr1)) For i = LBound(arr1) To UBound(arr1) arrayA(i) = arr1(i) * arr2(i) Next i multByElement = arrayA End If End Function As you can see, I'm trying to pass the string representation of the ranges. In the debugger I can see that they are properly passed in and the first visible problem occurs when it tries to read arr1(i) and shows as "subscript out of range". I have also tried passing in the range itself (ie range1 as Range...) but with no success. My best suspicion was that it has to do with the Active Sheet since it was called from a different sheet from the one with the formula (the sheet name is part of the string) but that was dispelled since I tried it both from within the same sheet and by specifying the sheet in the code. BTW, the formula in the cell looks like this: =AVERAGE(multByElement("A1:A3","B1:B3")) or =AVERAGE(multByElement("My Sheet1!A1:A3","My Sheet1!B1:B3")) for when I call it from a different sheet.

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• ColdFusion 9 ORM - Securing an object at a low level...

  Hiya: I wonder if anybody has an idea on this... I'm looking at securing a low level object in my model (a "member" object) so by default only certain information can be accessed from it. Here's a possible approach (damn sexy if it would work!): 1) Add a property called "locked" - defaulting to "true" to the object itself. It appears that the only option to do this, and not tie it to a db table column, is to use the formula attribute that takes a query. So to default locked to TRUE I've got: <cfproperty name="locked" formula="select 1" /> 2) Then, I overwrite the existing set-ers and get-ers to use this: e.g. <cffunction name="getFullname" returnType="string"> <cfscript> if (this.getLocked()) { return this.getScreenName(); } else { return this.getFullname(); } </cfscript> </cffunction> 3) When i use it like this: <p> #oMember.getFullName()# </p> shows the ScreenName (great!) but... When I do this: <cfset oMember.setLocked(false)> <p> #oMember.getFullName()# </p> Just hangs!!! It appears that attempting to set a property that's been defined using "formula" is a no-no. Any ideas? Any other way we can have properties attached to an ORM object that are gettable and settable without them being present in the db? Ideas appreciated!

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• Hibernate collection mapping Problem

  - by Geln Yang

  Hi, There is a table Item like, code,name 01,parent1 02,parent2 0101,child11 0102,child12 0201,child21 0202,child22 Create a java object and hbm xml to map the table.The Item.parent is a Item whose code is equal to the first two characters of its code : class Item{ String code; String name; Item parent; List<Item> children; .... setter/getter.... } <hibernate-mapping> <class name="Item" table="Item"> <id name="code" length="4" type="string"> <generator class="assigned" /> </id> <property name="name" column="name" length="50" not-null="true" /> <many-to-one name="parent" class="Item" not-found="ignore"> <formula> <![CDATA[ (select i.code,r.name from Item i where (case length(code) when 4 then i.code=SUBSTRING(code,1,2) else false end)) ]]> </formula> </many-to-one> <bag name="children"></bag> </class> </hibernate-mapping> I try to use formula to define the many-to-one relationship,but it doesn't work!Is there something wrong?Or is there other method? Thanks! ps,I use mysql database.

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• Hibernate mapping Problem

  - by Geln Yang

  Hi, There is a table Item like, code,name 01,parent1 02,parent2 0101,child11 0102,child12 0201,child21 0202,child22 Create a java object and hbm xml to map the table.The Item.parent is a Item whose code is equal to the first two characters of its code : class Item{ String code; String name; Item parent; List<Item> children; .... setter/getter.... } <hibernate-mapping> <class name="Item" table="Item"> <id name="code" length="4" type="string"> <generator class="assigned" /> </id> <property name="name" column="name" length="50" not-null="true" /> <many-to-one name="parent" class="Item" not-found="ignore"> <formula> <![CDATA[ (select i.code,r.name from Item i where (case length(code) when 4 then i.code=SUBSTRING(code,1,2) else false end)) ]]> </formula> </many-to-one> <bag name="children"></bag> </class> </hibernate-mapping> I try to use formula to define the many-to-one relationship,but it doesn't work!Is there something wrong?Or is there other method? Thanks! ps,I use mysql database.

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• Excel 2010: if( , , "") not treated the same as blank for pivot table group by date

  - by Confused

  I'm trying to group by date in an Excel 2010 pivot table. The column with dates (i.e., the one want to group by), should be the latest date of 2 other columns if neither is null, or blank. i.e., with a formula like: =IF(AND(A4 <> "", B4 <> ""), MAX(A4,B4), "") Normally, this ""in the IF() formula acts the same as an empty cell. In this case, it is preventing me from grouping by date in the Pivot Table. If I filter the date column by (Blanks), then clear the contents of all those cells, then the pivot table does group by date ok. i.e., "" is not being treated the same as an empty cell.

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• Automatically keeping two excel data tables in-sync (w/out VBA)

  - by Neil

  I'm putting together a workbook for tracking a stock portfolio. The primary sheet contains a table with the list of the transactions. From this I would like to create an overview table on another sheet with only one row per unique stock symbol that includes things like cost basis, returns, etc. The problem is that nothing I've tried updates the overview table correctly when rows are added to the transaction table. The closest I've got is something like the following: http://www.get-digital-help.com/2009/04/14/create-a-unique-alphabetically-sorted-list-extracted-from-a-column/ However, this requires applying that formula to every cell in the primary column of the overview sheet. And even then the range of the table isn't extended down to include new rows as they become valid. Essentially I'm looking for a way that auto-adds rows to a table and copies the formula based on a different table changing without using VBA. Trivial example data Sheet1 Symbol Type Shares Price F Buy 100 12 MSFT Buy 100 25 MSFT Sell 50 28 F Buy 100 16 Sheet2 Symbol Quantity F 200 MSFT 50

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• 255 Character limit on VLOOKUP

  - by zod

  Using excel 2003, the formula: =VLOOKUP(D1 ,A1:B135, 2) fails if the length of D1 exceeds 255 characters (i.e. the list has some text longer then 255 characters, D1 has the same text value, and VLOOKUP returns #VALUE!). MATCH seems to suffer from the same character limit. I cannot find any official confirmation of these limits, for example here: http://office.microsoft.com/en-us/excel-help/vlookup-HP005209335.aspx or here: http://office.microsoft.com/en-us/excel-help/excel-specifications-and-limits-HP005199291.aspx?CTT=3 I know that excel has a 255 limit on the length of text used in formulae, but it suggests connate should work (it does not in this case, and I am not using strings in the formula, but referencing another cell). Can somebody confirm that these limit exist (it is always possible I am doing something else wrong)? More importantly, does anyone know of a way around them? Thanks

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• LibreOffice Calc SEARCH and FIND functions

  - by TTT

  I am trying to process some data in Calc. One of the steps involve finding if a certain string is part of one of the column. I tried using FIND and SEARCH functions. Both behave in the same way and I am not getting correct results. E.g. Say I have following strings in Column A NY SF LON CAN US and am trying to put following formula in column C =SEARCH("NY",A2) The result is - cell C2 will have 1 (which is correct) but if the same formula is copied to other cells in column C - it gives me "#VALUE!" error and I am unable to find out why ? Any one has any ideas ? Thanks in advance TT

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• Val2 function in iWork Numbers?

  - by David.Chu.ca

  Is there equivalent Excel Val2() function in Numbers? I want to get value of a cell, which contains formula. What I need to get the result text from the cell. The following is example data: A B C ? 0 what? For example, in cell A1 I have a function like: =Right(C1) which is the end character of string in C1. Then I need to use the result of A1 in B1 =Count(C$1:C1, A1 = "?") As you can see, the result is 0. I think that A1 in above expression is referring to the formula of A1, instead of its result. Is there anything available like this in Numbers? =Count(C$1:C1, Val2(A1) = "?")

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• Excel: Conditional Formatting (Highlighting) Values Based on Another Worksheet

  - by ScottSEA

  I have a workbook that has two worksheets. The first worksheet is simply a list of the first 78,498 prime numbers in a single column, A1-A78498. The second worksheet has a grid of numbers from 1 to n. The goal is to highlight the cells with prime numbers in the grid by referencing the prime number values in the other worksheet. Is this possible, and if so, how? edit I have named the column with my prime numbers "PRIMES1T". I would like the formula to work for the entire worksheet, regardless of size, but my excel-fu is extremely weak. If at all possible, I would like to be able to enter the formula in the dialog box for conditional formatting (as below): I have tried =NOT(ISNA(MATCH(A:Z,PRIMES1T,0) (only A-Z, but have to start somewhere) with no luck.

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• Microsoft Excel IF/THEN statement for Words

  - by user1667462

  Right now I have an excel spreadsheet. In Cells A1 and down I have cities listed. In Cells B1 and down I have some generic information with the word CITY in it. What I want to know if there is a formula to replace the word CITY that is in the contents of Cell B1 with the contents in Cell A1. For instance... Cell A1 has "Daytona Beach, FL" Cell B1 has "Compare mortgage & refinance rates from different mortgage lenders and brokers in CITY. Find the home refinance rate you were looking for in CITY." I need a formula that replaces "CITY" in B1 with "Dayton Beach, FL" in A1. Is this possible? Thank you for your help!

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• COUNTIFS over multiple worksheets

  - by Alison

  I am trying to make COUNTIFS go across two worksheets in the same excel file (Final Driver Forecast Model), just on different tabs. I need it to count if a driver returns between a certain time, then to put a 1 in that time slot. For example if a driver returns at 2:30 p.m. on the 27th, then the formula will put in a 1 in the July 27th slot from 2:00 p.m.-4:00 p.m. I have tried two different formulas the first is =COUNTIF3D(Bid Sheet '[1]Bid Sheet 1'!O4:O110,">="&B76,O4:O110,"<="&C76) This is looking at the worksheet called Bid Sheet 1 and the column O4 through O110 and deciding if the time fits in the time slot of B76 00:00 (12 a.m.) and C 76 2:00 a.m. The second formula I tried to do the exact same thing =COUNTIF3D(O4:O110,">="B76,O4:O110,"<="&C76,"FinalDriverForecastModel',Bid Sheet 1") Neither is working and they both give me #NAME? when I hit enter......What am I doing wrong?

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• Showing name of row instead of excel cell name

  - by Kare

  I am having extremely long formulas over an extremely big sheet. At the moment I am tracking the formulas with the Formula Auditing Tool. However, my idea would be to just replace for example in a formula like this: =IF(AND(ROUND($GX19-SUM(0)/$M$12;2)<=0;$AK$7=1);0;$M$12*$M$22/$K$62 My idea would be to replace the excel cell names with the table row names they are in. Like: =IF(AND(ROUND( "Income" -SUM(0)/ "Debt" ;2)<=0; "Percentage" =1);0; "Investment" * "Debt of house" / "Investment costs" Is there any way to achive sth. like that in excel? I appreciate your inputs!!!

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• displaying python's autodoc to the user (python 3.3)

  - by Plotinus

  I'm writing a simple command line math game, and I'm using python's autodoc for my math algorithms to help me remember, for example, what a proth number is while i'm writing the algorithm, but later on I'll want to tell that information to the user as well, so they'll know what the answer was. So, for example I have: def is_proth(): """Proth numbers and numbers that fit the formula k×2^n + 1, where k are odd positive integers, and 2^n > k.""" [snip] return proths and then I tried to make a dictionary, like so: definitions = {"proths" : help(is_proth)} But it doesn't work. It prints this when I start the program, one for each item in the dictionary, and then it errors out on one of them that returns a set. And anyway, I don't want it displayed to the user until after they've played the game. Help on function is_proth in module __main__: is_proth() Proth numbers and numbers that fit the formula k×2^n + 1, where k are odd positive integers, and 2^n > k. (END) I understand the purpose of autodoc is more for helping programmers who are calling a function than for generating userdoc, but it seems inefficient to have to type out the definition of what a proth number is twice, once in a comment to help me remember what an algorithm does and then once to tell the user the answer to the game they were playing after they've won or lost.

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• Implement Budget Allocation in DAX for Power Pivot and Tabular #powerpivot #tabular #ssas #dax

  - by Marco Russo (SQLBI)

  Comparing sales and budget, or costs and budget, is a very common operation. However, it is often the case that you have different granularities for different tables containing budget and the data to compare with. There are two ways to do that: you can limit the comparison to the granularity that is common to the two tables, or you can allocate the budget where it’s not defined. For example, if you have a budget defined by quarter and category, you might want to allocate it by month and product. In this way, you will do the comparison as you had a more granular definition of the budget, without actually having to do the manual job of allocating data (usually in an Excel worksheet!). If you want to do budget allocation in DAX, you can use the Budget Patterns we published on DAX Patterns. If you come from and MDX/OLAP background, at first you might find it hard to solve the problem of not having attribute hierarchies that helps you in propagating the budget values to lower hierarchical levels. However, I think that once you get used to DAX, you will find the behavior very predictable and easy to “debug” also for more complex allocation formula. You just have to be careful in writing the DAX formula, but probably the pattern we wrote should help you designing the right data model, without creating physical relationships to the budget table! This pattern is also based on the Handling Different Granularities scenario I discussed a couple of weeks ago.

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• How do you put price on your source code?

  - by deviDave

  I was asked to sell the source code of small utility app I did years ago with existing users of this app. I tried investigating how to put price on the source code and haven't come up with a good solution so far. I first tried searching the net, but information I found there are somehow far from reality. Then I found a few people how also sold their source code with users as well. But their price seems unrealistic (too high). For example, one person had an app which price was around $200 for 1 user and he had 80 users. He sold the source with users for $30k. How did he come up with this price? Is it a good price if I charge the code by formula: num_of_users x app_price + app_price x num_of_new_users_in_one_year ? This means that I count the price by selling each user for the price of the app then adding the amount of money I earn in 1 year from this app. If this is a good formula, what shall I do with sources who do not have users yet?

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• Monster's AI in an Action-RPG

  - by Andrea Tucci

  I'm developing an action rpg with some University colleagues. We've gotton to the monsters' AI design and we would like to implement a sort of "utility-based AI" so we have a "thinker" that assigns a numeric value on all the monster's decisions and we choose the highest (or the most appropriate, depending on monster's iq) and assign it in the monster's collection of decisions (like a goal-driven design pattern) . One solution we found is to write a mathematical formula for each decision, with all the important parameters for evaluation (so for a spell-decision we might have mp,distance from player, player's hp etc). This formula also has coefficients representing some of monster's behaviour (in this way we can alterate formulas by changing coefficients). I've also read how "fuzzy logic" works; I was fascinated by it and by the many ways of expansion it has. I was wondering how we could use this technique to give our AI more semplicity, as in create evaluations with fuzzy rules such as IF player_far AND mp_high AND hp_high THEN very_Desiderable (for a spell having an high casting-time and consume high mp) and then 'defuzz' it. In this way it's also simple to create a monster behaviour by creating ad-hoc rules for every monster's IQ category. But is it correct using fuzzy logic in a game with many parameters like an rpg? Is there a way of merging these two techniques? Are there better AI design techniques for evaluating monster's chooses?

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• SQL SERVER – Introduction to PERCENT_RANK() – Analytic Functions Introduced in SQL Server 2012

  - by pinaldave

  SQL Server 2012 introduces new analytical functions PERCENT_RANK(). This function returns relative standing of a value within a query result set or partition. It will be very difficult to explain this in words so I’d like to attempt to explain its function through a brief example. Instead of creating a new table, I will be using the AdventureWorks sample database as most developers use that for experiment purposes. Now let’s have fun following query: USE AdventureWorks GO SELECT SalesOrderID, OrderQty, RANK() OVER(ORDER BY SalesOrderID) Rnk, PERCENT_RANK() OVER(ORDER BY SalesOrderID) AS PctDist FROM Sales.SalesOrderDetail WHERE SalesOrderID IN (43670, 43669, 43667, 43663) ORDER BY PctDist DESC GO The above query will give us the following result: Now let us understand the resultset. You will notice that I have also included the RANK() function along with this query. The reason to include RANK() function was as this query is infect uses RANK function and find the relative standing of the query. The formula to find PERCENT_RANK() is as following: PERCENT_RANK() = (RANK() – 1) / (Total Rows – 1) If you want to read more about this function read here. Now let us attempt the same example with PARTITION BY clause USE AdventureWorks GO SELECT SalesOrderID, OrderQty, ProductID, RANK() OVER(PARTITION BY SalesOrderID ORDER BY ProductID ) Rnk, PERCENT_RANK() OVER(PARTITION BY SalesOrderID ORDER BY ProductID ) AS PctDist FROM Sales.SalesOrderDetail s WHERE SalesOrderID IN (43670, 43669, 43667, 43663) ORDER BY PctDist DESC GO Now you will notice that the same logic is followed in follow result set. I have now quick question to you – how many of you know the logic/formula of PERCENT_RANK() before this blog post? Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: Pinal Dave, PostADay, SQL, SQL Authority, SQL Function, SQL Query, SQL Scripts, SQL Server, SQL Tips and Tricks, T SQL, Technology

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• Implement Budget Allocation in DAX for Power Pivot and Tabular #powerpivot #tabular #ssas #dax

  - by Marco Russo (SQLBI)

  Comparing sales and budget, or costs and budget, is a very common operation. However, it is often the case that you have different granularities for different tables containing budget and the data to compare with. There are two ways to do that: you can limit the comparison to the granularity that is common to the two tables, or you can allocate the budget where it’s not defined. For example, if you have a budget defined by quarter and category, you might want to allocate it by month and product. In this way, you will do the comparison as you had a more granular definition of the budget, without actually having to do the manual job of allocating data (usually in an Excel worksheet!). If you want to do budget allocation in DAX, you can use the Budget Patterns we published on DAX Patterns. If you come from and MDX/OLAP background, at first you might find it hard to solve the problem of not having attribute hierarchies that helps you in propagating the budget values to lower hierarchical levels. However, I think that once you get used to DAX, you will find the behavior very predictable and easy to “debug” also for more complex allocation formula. You just have to be careful in writing the DAX formula, but probably the pattern we wrote should help you designing the right data model, without creating physical relationships to the budget table! This pattern is also based on the Handling Different Granularities scenario I discussed a couple of weeks ago.

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• Takeaways From CSO Roundtable New York

  - by Naresh Persaud

  Thanks to everyone who attended the Chief Security Officer Roundtable in New York last week. We were lucky to have Dennis Brixus, CSO of McGraw-Hill  as a guest speaker. In addition, Jeff Henley, provided a board level perspective on security. Amit Jasuja discussed Oracle's security formula.  A few takeaways from Jeff's talk that were interesting: Security is a board level issue. The challenge at the board level is that boards have short attention span. The CSO needs to be vigilant in educating the board on the strategic importance of security. Every CSO needs to think about cost. The CSO has to look at the economics of security and demonstrate fiduciary responsibility. We have to think of security as a business enabler. Security is the enabler that helps us expand into new markets and connect better with our customers and partners. While the CSO can't prevent every threat, we have to expect the CSO to have a plan. Oracle security-formula View more PowerPoint from OracleIDM

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• How AlphaBlend Blendstate works in XNA when accumulighting light into a RenderTarget?

  - by cubrman

  I am using a Deferred Rendering engine from Catalin Zima's tutorial: His lighting shader returns the color of the light in the rgb channels and the specular component in the alpha channel. Here is how light gets accumulated: Game.GraphicsDevice.SetRenderTarget(LightRT); Game.GraphicsDevice.Clear(Color.Transparent); Game.GraphicsDevice.BlendState = BlendState.AlphaBlend; // Continuously draw 3d spheres with lighting pixel shader. ... Game.GraphicsDevice.BlendState = BlendState.Opaque; MSDN states that AlphaBlend field of the BlendState class uses the next formula for alphablending: (source × Blend.SourceAlpha) + (destination × Blend.InvSourceAlpha), where "source" is the color of the pixel returned by the shader and "destination" is the color of the pixel in the rendertarget. My question is why do my colors are accumulated correctly in the Light rendertarget even when the new pixels' alphas equal zero? As a quick sanity check I ran the following code in the light's pixel shader: float specularLight = 0; float4 light4 = attenuation * lightIntensity * float4(diffuseLight.rgb,specularLight); if (light4.a == 0) light4 = 0; return light4; This prevents lighting from getting accumulated and, subsequently, drawn on the screen. But when I do the following: float specularLight = 0; float4 light4 = attenuation * lightIntensity * float4(diffuseLight.rgb,specularLight); return light4; The light is accumulated and drawn exactly where it needs to be. What am I missing? According to the formula above: (source x 0) + (destination x 1) should equal destination, so the "LightRT" rendertarget must not change when I draw light spheres into it! It feels like the GPU is using the Additive blend instead: (source × Blend.One) + (destination × Blend.One)

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• How to translate formulas into form of natural language?

  - by Ricky

  I am recently working on a project aiming at evaluating whether an android app crashes or not. The evaluation process is 1.Collect the logs(which record the execution process of an app). 2.Generate formulas to predict the result (formulas is generated by GP) 3.Evaluate the logs by formulas Now I can produce formulas, but for convenience for users, I want to translate formulas into form of natural language and tell users why crash happened.(I think it looks like "inverse natural language processing".) To explain the idea more clearly, imagine you got a formula like this: 155 - count(onKeyDown) >= 148 It's obvious that if count(onKeyDown) 7, the result of "155 - count(onKeyDown) = 148" is false, so the log contains more than 7 onKeyDown event would be predicted "Failed". I want to show users that if onKeyDown event appears more than 7 times(155-148=7), this app will crash. However, the real formula is much more complicated, such as: (< !( ( SUM( {Att[17]}, Event[5]) <= MAX( {Att[7]}, Att[0] >= Att[11]) OR SUM( {Att[17]}, Event[5]) > MIN( {Att[12]}, 734 > Att[19]) ) OR count(Event[5]) != 1 ) > (< count(Att[4] = Att[3]) >= count(702 != Att[8]) + 348 / SUM( {Att[13]}, 641 < Att[12]) mod 587 - SUM( {Att[13]}, Att[10] < Att[15]) mod MAX( {Att[13]}, Event[2]) + 384 > count(Event[10]) != 1)) I tried to implement this function by C++, but it's quite difficult, here's the snippet of code I am working right now. Does anyone knows how to implement this function quickly?(maybe by some tools or research findings?)Any idea is welcomed: ) Thanks in advance.

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