aCalcout - Array Calculation Output Record

1. Introduction

The Array Calculation Output or "aCalcout" record is derived from the sCalcout (string calcout) record, which, in turn, is derived from the calcout record. The aCalcout record extends the calcout record by supporting array operands and expressions in addition to scalar operands and expressions. The record has 12 array fields (AA...LL) used as input variables for the expression, and it calls an extended version of the EPICS calculation engine that knows about arrays. The aCalcout record's output link is intended to write array or scalar data depending on the data type of the field to which it is linked, but this hasn't been implemented yet.

Here's a sample MEDM display of some of the the aCalcout record fields.


userArrayCalc.adl

 

2. Scan Parameters

The aCalcout record has the standard fields for specifying under what circumstances the record will be processed. See the EPICS Record Reference Manual for these fields and their use.

 

3. Input Links

The aCalcout record has 24 links with which it fetches values for use in expressions: 12 to scalar fields (INPA -> A, INPB -> B, . . . INPL -> L); and 12 to array fields (INAA -> AA, INBB -> BB, ...INLL -> LL). The fields can be database links, channel access links, or (scalar-fields only) constants. These link fields cannot be hardware addresses. In addition, the aCalcout record contains the fields INAV, INBV, . . . INLV, which indicate the status of the links to scalar fields, and the fields IAAV, IBBV, . . . ILLV, which indicate the status of the links to array fields.  These fields indicate whether or not the specified PV was found and a link to it established. See Section 6, Display Parameters for an explanation of these fields.

 See the EPICS Record Reference Manual for information on how to specify database links.
Field Summary Type DCT Initial Access Modify Rec Proc Monitor
INPA Input Link A INLINK Yes 0 No No N/A
INPB Input Link B INLINK Yes 0 No No N/A
... ... ... ... ... ... ... ...
INPL Input Link L INLINK Yes 0 No No N/A
INAA Input Link AA INLINK Yes 0 No No N/A
INBB Input Link BB INLINK Yes 0 No No N/A
... ... ... ... ... ... ... ...
INFLL Input Link LL INLINK Yes 0 No No N/A

 

4. Expressions

Like the Calcout record, the aCalcout record has a CALC field into which you can enter an expression for the record to evaluate when it processes. The resulting scalar value will be placed in the VAL field, and the resulting array value will be placed in the AVAL field. VAL can then be used by the OOPT field (see Section 5, Output Parameters) to determine whether or not to write to the output link or post an output event. Either VAL and AVAL can also be written to the output link. (If you elect to write an output value, the record will choose between VAL and AVAL, depending on the data type of the field at the other end of the output link.)

The CALC expression is actually converted to opcodes and stored in postfix notation in the RPCL field. It is this postfix expression which is actually evaluated. When the CALC field is changed at run-time, the record-support routine special() calls a function to check it, convert it to postfix, and evaluate it.
The record also has a second set of calculation-related fields described in Section 5, Output Parameters.
 
Field Summary Type DCT Initial Access Modify Rec Proc Monitor PP
CALC Calculation STRING[36] Yes 0 Yes Yes Yes No
VAL Value DOUBLE No 0 Yes Yes Yes No
RPCL Postfix NOACCESS No 0 No No N/A No
AVAL Array value DOUBLE No 0 Yes Yes Yes No

Expressions supported by the array calculation record can involve operands, algebraic operators and functions, trigonometric functions, relational operators, logical operators, array operators and functions, parentheses and commas, and the conditional '?:' operator. The expression can consist of any of these operators, as well as any of the values from the scalar and array input fields, which are the operands.

Unless otherwise stated, functions and operators behave as follows:

4.1. Operands

The expression can use the values retrieved from the input links as operands. These values retrieved from the input links are stored in the A-L, and AA-LL fields. The values to be used in the expression are simply referenced by the field name. For example, the values obtained from the INPA link is stored in the field A, and is referred to in an expression as 'A' (or 'a' -- case doesn't matter).

The number of elements of the array operands AA-LL is set at boot time by the field NELM. If an array value is received by the record with more or fewer elements, the array used by the aCalcout record will be truncated or padded at the end with zeros.

Field Summary Type DCT Initial Access Modify Rec Proc Monitor PP
A Input Value A DOUBLE No 0 Yes Yes/No* Yes Yes
B Input Value B DOUBLE No 0 Yes Yes/No* Yes Yes
... ... ... ... ... ... ... ... ...
L Input Value L DOUBLE No 0 Yes Yes/No* Yes Yes
AA Input array AA DOUBLE ARRAY No 0 Yes Yes/No* Yes Yes
BB Input array BB DOUBLE ARRAY No 0 Yes Yes/No* Yes Yes
... ... ... ... ... ... ... ... ...
LL Input array LL DOUBLE ARRAY No 0 Yes Yes/No* Yes Yes

* If a valid input link is associated with this field, then the record will not not permit it to be modified by a 'put' operation.

There are a few special operands not associated with input fields, but defined by the record (more exactly, defined by the calc engine the record uses to evaluate expressions). All but RNDM and ARNDM are constants.

PI 3.141592654
D2R Degrees to radians (PI/180)
R2D Radians to degrees (1/D2R)
S2R Arc seconds to radians (D2R/3600)
R2S Radians to arc seconds (1/S2R)
RNDM Random number between 0 and 1.
ARNDM Array of random numbers between 0 and 1.
IX Array [0,1,2,...].

4.2. Algebraic Functions/Operators

Op Description Example
ABS Absolute value (one-argument function) ABS(A)
SQRT Square root (one-argument function) (SQR is deprecated) SQRT(A)
MIN Minimum (two-argument function) MIN(A,B)
MAX Maximum (two-argument function) MAX(A,B)
CEIL Ceiling (one-argument function) CEIL(A)
FLOOR Floor (one-argument function) FLOOR(A)
INT Nearest integer (one-argument function) INT(A)
NINT Nearest integer (one-argument function) NINT(A)
LOG Log base 10 (one-argument function) LOG(A)
LN Natural logarithm (one-argument function) LN(A)
LOGE Deprecated synonym for 'LN' LOGE(A)
EXP Exponential function (unary) EXP(A)
^ Exponential (binary) (Same as '**'.) A^B
** Exponential (binary) (Same as '^'.) A**B
+ Addition (binary) A+B
- Subtraction (binary) A-B
* Multiplication (binary) A*B
/ Division (binary) A/B
% Modulo (binary) A%B
- Negate (unary) -A
NOT Negate (unary) NOT A
>& Max (binary) A>?B
<& Min (binary) A<?B

4.3. Trigonometric Functions

Op Description Example
SIN Sine (one-argument function) SIN(A)
SINH Hyperbolic sine (one-argument function) SINH(A)
ASIN Arc sine (one-argument function) ASIN(A)
COS Cosine (one-argument function) COS(A)
COSH Hyperbolic cosine (one-argument function) COSH(A)
ACOS Arc cosine (one-argument function) ACOS(A)
TAN Tangent (one-argument function) TAN(A)
TANH Hyperbolic tangent (one-argument function) TANH(A)
ATAN Arc tangent (one-argument function) ATAN(A)
ATAN2 Alternate form of arctangent (two-argument function) ATAN2(A,B)

4.4. Relational Operators

Op Description Example
>= Greater than or equal to A>=B
> Greater than A>B
<= Less than or equal to A<=B
< Less than A<B
!= Not equal to (same as '#') A!=B
# Not equal to (same as '!=') A#B
== Equal to (same as '=') A==B
= Equal to (same as '==') A=B

4.5. Logical Operators

Op Description Example
&& Logical AND A&&B
|| Logical OR A||B
! Logical NOT !A

4.6. Bitwise Operators

Op Description Example
| Bitwise OR A|B
OR Bitwise OR A OR B
& Bitwise AND A&B
AND Bitwise AND A AND B
XOR Bitwise Exclusive OR A XOR B
~ One's Complement ~A
<< Left shift A<<B
>> Right shift A>>B

4.7. Separators

The open and close parentheses are supported. Nested parenthesis are supported. Square and curly brackets are not available for use as separators, because they are being used as operators.
The comma is supported when used to separate the arguments of a binary function.
Spaces may occur between expression elements. Space is required between elements that would otherwise be parsed incorrectly. The parser always attempts to match the largest string of characters that constitute a recognized operator or variable. For example, A AND B could be shortened to A ANDB, because ANDB will be parsed as AND B. However, A AND B may not be shortened to AAND B, because AAND would be parsed as AA ND.

4.8. Conditional Expression

The C language's if-else (?:") operator is supported. The format is: 
 <expression> ? <expression-true result> : <expression-false  result>

4.9. Array-specific Functions/Operators

Most of the functions and operators that can work with arrays are simple generalizations of functions and operators that work with scalars. Such functions are not listed here. In this section are those functions or operators that apply only to arrays, and whose behavior is not a simple element-by-element rendition of some scalar function.

Op Description Example
AMIN Minimal element of array (one-argument function) AMIN(AA) -> scalar
AMAX Maximal element of array (one-argument function) AMAX('a','b','c') -> 'c'
ARR Convert argument to array (one-argument function) ARR(1) -> 1, 1, 1,...
[ Subarray AA[1,3] -> aa(1),aa(2),aa(3)
{ Subarray in place AA[1,3] -> 0, aa(1),aa(2),aa(3), 0,...
>> Array shift right. Move array elements by index. AA>>2
<< Array shift left. Move array elements by index. AA<<2 (same as AA>>-2)
AVG Average of array values AVG(AA)
STD Standard deviation of array values STD(AA)

4.10. Argument-array Operators

These operators represent the scalar/array fields of the aCalcout record as arrays of scalars/arrays. They are an alternative way of specifying the fields A-L and AA-LL.

Op Description Example
@ Scalar array element. Regard the numeric fields A-L as an array whose elements are numbered 0-11, and return the element whose number follows. Thus, @0 is another way of saying A. (unary operator) @A
@@ Array array element. Regard the array fields AA-LL as an array of arrays whose elements are numbered 0-11, and return the element whose number follows. Thus, @@1 is another way of saying BB. (unary operator) @@A

4.11. Examples

Algebraic

A + B + 10
Result is A + B + 10

Relational

(A + B) < (C + D)
Result is 1 if (A+B) < (C+D)
Result is 0 if (A+B) >= (C+D)

If-Else

(A+B)<(C+D)?E:F+L+10
Result is E if (A+B) < (C+D)
Result is F+L+10 if (A+B) >= (C+D)

(A+B)<(C+D)?E
Result is E if (A+B) < (C+D)
Result is unchanged if (A+B) >= (C+D)

Logical

A&B
Causes the following to occur:
  1. Convert A to integer
  2. Convert B to integer
  3. Perform bit-wise AND of A and B
  4. Convert result to floating point

Array

Notation: I'll use (1,2,3) to indicate an array. Note that [1,2] is not an array, but the subrange operator with arguments 1 and 2. The subrange operator must follow an array, like so: AA[2,5]. Similarly, {1,2} is not an array, but the subrange-in-place operator.

A + AA
where A=1 and AA = (1,2,3)
Result is (2,3,4).

A + DBL(AA)
where A=1 and AA=(1,2,3)
Result is 2. DBL returns the first array element.

AA+BB
where AA=(1,2,3) and BB=(7,8,9)
Result is (8,10,12). Element-by-element sum. Most operators behave in this way.

AA[2,4]
where AA = (1,2,3,4,5)
Result is (3,4,5).  (The first element of an array is numbered "0".)

AA[-3,-1]
where AA=(1,2,3,4)
Result is (2,3,4).  (The last element of an array is numbered "-1".)

AA{2,4}
where AA = (1,2,3,4,5,6)
Result is (0,0,3,4,5,0).  (Similar to the [] operator, but the selected subrange is left in place.)

Argument-array

@0
Result is the value of the numeric variable A. ("@0" is just another name for A.)

@@0
Result is the value of the array variable AA.

@(A+B)
Result is the value of the numeric variable whose number is given by the sum of A and B.

 

5. Output Parameters

These parameters specify and control the output capabilities of the aCalcout record. They determine when to write the output, where to write it, and what the output will be. The OUT link specifies the Process Variable to which the result will be written. The OOPT field determines the condition that causes the output link to be written to. It's a menu field that has six choices:

Every Timewrite output every time record is processed.
On Changewrite output every time VAL changes, i.e., every time the result of the expression changes.
When Zerowhen record is processed, write output if VAL is zero.
When Non-zerowhen record is processed, write output if VAL is non-zero.
Transition to Zerowhen record is processed, write output only if VAL is zero and last value was non-zero.
Transition to Non-zerowhen record is processed, write output only if VAL is non-zero and last value was zero.
NeverDon't write output ever.

  The DOPT field determines what data is written to the output link when the output is executed. The field is a menu field with two options: Use CALC or Use OCAL. If Use CALC is specified, when the record writes its output it will write the result of the expression in the CALC field, that is, it will write the value of the VAL [AVAL] field to a double [array] destination. If Use OCAL is specified, the record will instead write the result of the expression in the OCAL field, which result is contained in the OVAL field (array result in the OAV field). The OCAL field is exactly analogous to the CALC field and has the same functionality: it can contain an expression which is evaluated at run-time. Thus, if necessary, the record can use the result of the CALC expression to determine if data should be written and can use the result of the OCAL expression as the data to write.

 If the OEVT field specifies a non-zero integer and the condition in the OOPT field is met, the record will post a corresponding event. If the ODLY field is non-zero, the record pauses for the specified number of seconds before executing the OUT link or posting the output event. During this waiting period the record is "active" and will not be processed again until the wait is over. The field DLYA is equal to 1 during the delay period. The resolution of the delay entry is one clock tick, where the clock frequency is defined elsewhere (see epicsThreadSleepQuantum() in the EPICS Application Developer's Guide).

 The IVOA field specifies what action to take with the OUT link if the aCalcout record enters an INVALID alarm status. The options are Continue normally, Don't drive outputs, and Set output to IVOV. If the IVOA field is Set output to IVOV, the data entered into the IVOV field is written to the OUT link if the record alarm severity is INVALID.

Field Summary Type DCT Initial Access Modify Rec Proc Monitor PP
OUT Output Specification OUTLINK Yes 0 Yes Yes N/A No
OOPT Output Execute Option Menu Yes 0 Yes Yes No No
DOPT Output Data Option Menu Yes 0 Yes Yes No No
OCAL Output Calculation STRING[36] Yes Null Yes Yes No No
OVAL Output Value DOUBLE No 0 Yes Yes Yes No
OEVT Event To Issue SHORT Yes 0 Yes Yes No No
ODLY Output Execution Delay FLOAT Yes 0 Yes Yes No No
IVOV Invalid Output Action Menu Yes 0 Yes Yes No No
IVOA Invalid Output Value DOUBLE Yes 0 Yes Yes No No
OAV Output array value DOUBLE ARRAY NO 0 Yes Yes Yes No
WAIT Wait for completion? Menu Yes "NoWait" Yes Yes Yes No

The aCalcout record uses device support to write to the OUT link. Soft device supplied with the record is selected with the .dbd specification 

 field(DTYP,"Soft Channel")
This device support uses the record's WAIT field to determine whether to wait for completion of processing initiated by the OUT link before causing the record to execute its forward link. The mechanism by which this waiting for completion is performed requires that the OUT link have the attribute CA -- i.e., the link text looks something like

xxx:record.field CA NMS

Currently, the record does not try to ensure that WAIT and OUT are compatibly configured. If WAIT == "Wait", but the link looks like

xxx:record.field PP NMS

for example, then the record will not wait for completion before executing its forward link.

 

6. Display Parameters

These parameters are used to present meaningful data to the operator. Some are also meant to represent the status of the record at run-time. An example of an interactive MEDM display screen that displays the status of the aCalcout record is located here.

The EGU field contains a string of up to 16 characters which is supplied by the user and which describes the values being operated upon. The string is retrieved whenever the routine get_units is called. The EGU string is solely for an operator's sake and does not have to be used.

The HOPR and LOPR fields only refer to the limits of the VAL, HIHI, HIGH, LOW, and LOLO fields. PREC controls the precision of the VAL field.

The INAV-INLV and IAAV-ILLV fields indicate the status of the link to the PVs specified in the INPA-INPL and INAA-INLL fields, respectively. The fields can have three possible values:

 
Ext PV NC the PV wasn't found on this IOC and a Channel Access link hasn't been established.
Ext PV OK the PV wasn't found on this IOC and a Channel Access link has been established.
Local PV the PV was found on this IOC.
Constant the corresponding link field is a constant.

The OUTV field indicates the status of the OUT link. It has the same possible values as the INAV-INLV fields.

The CLCV and OLCV fields indicate the validity of the expression in the CALC and OCAL fields, respectively. If the expression is invalid, the field is set to one.

The DLYA field is set to one during the delay interval specified in ODLY.

See the EPICS Record Reference Manual, for more on the record name (NAME) and description (DESC) fields.

Field Summary Type DCT Initial Access Modify Rec Proc Monitor PP
EGU Engineering Units STRING [16] Yes Null Yes Yes No No
PREC Display Precision SHORT Yes 0 Yes Yes No No
HOPR High Operating Range FLOAT Yes 0 Yes Yes No No
LOPR Low Operating Range FLOAT Yes 0 Yes Yes No No
INAV Link Status of INPA Menu No 1 Yes No No No
INBV Link Status of INPB Menu No 1 Yes No No No
... ... ... ... ... ... ... ... ...
INLV Link Status of INPL Menu No 1 Yes No No No
OUTV OUT PV Status Menu No 0 Yes No No No
CLCV CALC Valid LONG No 0 Yes Yes No No
OCLV OCAL Valid LONG No 0 Yes Yes No No
DLYA Output Delay Active USHORT No 0 Yes No No No
NAME Record Name STRING [29] Yes 0 Yes No No No
DESC Description STRING [29] Yes Null Yes Yes No No
IAAV Link Status of INAA Menu No 1 Yes No No No
IBBV Link Status of INBB Menu No 1 Yes No No No
... ... ... ... ... ... ... ... ...
ILLV Link Status of INLL Menu No 1 Yes No No No
 

7. Alarm Parameters

The possible alarm conditions for the aCalcout record are the SCAN, READ, Calculation, and limit alarms. The SCAN and READ alarms are called by the record support routines. The Calculation alarm is called by the record processing routine when the CALC expression is an invalid one, upon which an error message is generated.

 The following alarm parameters which are configured by the user define the limit alarms for the VAL field and the severity corresponding to those conditions.

 The HYST field defines an alarm deadband for each limit. See the EPICS Record Reference Manual for a complete explanation of alarms and these fields.

Field Summary Type DCT Initial Access Modify Rec Proc Monitor PP
HIHI Hihi Alarm Limit FLOAT Yes 0 Yes Yes No Yes
HIGH High Alarm Limit FLOAT Yes 0 Yes Yes No Yes
LOW Low Alarm Limit FLOAT Yes 0 Yes Yes No Yes
LOLO Lolo Alarm Limit FLOAT Yes 0 Yes Yes No Yes
HHSV Severity for a Hihi Alarm Menu Yes 0 Yes Yes No Yes
HSV Severity for a High Alarm Menu Yes 0 Yes Yes No Yes
LSV Severity for a Low Alarm Menu Yes 0 Yes Yes No Yes
LLSV Severity for a Lolo Alarm Menu Yes 0 Yes Yes No Yes
HYST Alarm Deadband DOUBLE Yes 0 Yes Yes No No
 

8. Monitor Parameters

These parameters are used to determine when to send monitors for the value fields. The monitors are sent when the value field exceeds the last monitored field by the appropriate deadband, the ADEL for archiver monitors and the MDEL field for all other types of monitors. If these fields have a value of zero, every time the value changes, monitors are triggered; if they have a value of -1, every time the record is scanned, monitors are triggered.
Field Summary Type DCT Initial Access Modify Rec Proc Monitor PP
ADEL Archive Deadband DOUBLE Yes 0 Yes Yes No No
MDEL Monitor, i.e. value change, Deadband DOUBLE Yes 0 Yes Yes No No
 

9. Run-time Parameters

These fields are not configurable using a configuration tool and none are modifiable at run-time. They are used to process the record.

 The LALM field is used to implement the hysteresis factor for the alarm limits.

 The LA-LL fields are used to decide when to trigger monitors for the corresponding fields. For instance, if LA does not equal the value for A, monitors for A are triggered. The MLST and MLST fields are used in the same manner for the VAL field.

Field Summary Type DCT Initial Access Modify Rec Proc Monitor PP
LALM Last Alarmed Value DOUBLE No 0 Yes No No No
ALST Archive Last Value DOUBLE No 0 Yes No No No
MLST Monitor Last Value DOUBLE No 0 Yes No No No
LA Previous Input Value for A DOUBLE No 0 Yes No No No
LB Previous Input Value for B DOUBLE No 0 Yes No No No
... ... ... ... ... ... ... ... ...
LL Previous Input Value for A DOUBLE No 0 Yes No No No
LAA Previous Input Value for AA DOUBLE ARRAY No 0 Yes No No No
LBB Previous Input Value for BB DOUBLE ARRAY No 0 Yes No No No
... ... ... ... ... ... ... ... ...
LLL Previous Input Value for LL DOUBLE ARRAY No 0 Yes No No No
 

10. Record Support Routines

init_record

For each constant input link, the corresponding value field is initialized with the constant value if the input link is CONSTANT or a channel access link is created if the input link is PV_LINK.

 A routine postfix is called to convert the infix expression in CALC and OCAL to reverse polish notation. The result is stored in RPCL and ORPC, respectively.

 

process

See section 11.

 

special

This is called if CALC or OCAL is changed. special calls aCalcPostfix.

 

get_value

Fills in the values of struct valueDes so that they refer to VAL.

 

get_units

Retrieves EGU.

 

get_precision

Retrieves PREC.

 

get_graphic_double

Sets the upper display and lower display limits for a field. If the field is VAL, HIHI, HIGH, LOW, or LOLO, the limits are set to HOPR and LOPR, else if the field has upper and lower limits defined they will be used, else the upper and lower maximum values for the field type will be used.

 

get_control_double

Sets the upper control and the lower control limits for a field. If the field is VAL, HIHI, HIGH, LOW, or LOLO, the limits are set to HOPR and LOPR, else if the field has upper and lower limits defined they will be used, else the upper and lower maximum values for the field type will be used.

 

get_alarm_double

Sets the following values:

 upper_alarm_limit = HIHI

 upper_warning_limit = HIGH

 lower_warning_limit = LOW

 lower_alarm_limit = LOLO

 

11. Record Processing

11.1. process()

The process() routine implements the following algorithm:

 

1. Fetch all arguments.

 

2. Call routine aCalcPerform(), which calculates VAL from the postfix version of the expression given in CALC. If aCalcPerform() returns success, UDF is set to FALSE.

 

3. Check alarms. This routine checks to see if the new VAL causes the alarm status and severity to change. If so, NSEV, NSTA and LALM are set. It also honors the alarm hysteresis factor (HYST). Thus the value must change by at least HYST before the alarm status and severity changes.

 

4. Determine if the Output Execution Option (OOPT) is met. If it is met, either execute the output link (and output event) immediately (if ODLY = 0), or schedule a callback to do so after the specified interval. See the explanation for the execOutput() routine below.

 

5. Check to see if monitors should be invoked.

 

6. If no output delay was specified, scan forward link if necessary, set PACT FALSE, and return.

 

11.2. execOutput()

1. If DOPT field specifies the use of OCAL, call the routine aCalcPerform for the postfix version of the expression in OCAL. Otherwise, use VAL.

 

2. If the Alarm Severity is INVALID, follow the option as designated by the field IVOA.

 

3. If the Alarm Severity is not INVALID or IVOA specifies "Continue Normally", call device support to write the value of OVAL to device or PV specified by the OUT link, and post the event in OEVT (if non-zero).

 

4. If an output delay was implemented, process the forward link.

 

1. - Introduction
2. - Scan Parameters
3. - Input Links
4. - Expressions
4.1. - Operands
4.2. - Algebraic Functions/Operators
4.3. - Trigonometric Functions
4.4. - Relational Operators
4.5. - Logical Operators
4.6. - Bitwise Operators
4.7. - Separators
4.8. - If-Else
4.9. - Array-specific Functions/Operators
4.10. - Argument-array Operators
4.11. - Examples
5. - Output Parameters
6. - Display Parameters
7. - Alarm Parameters
8. - Monitor Parameters
9. - Run-time Parameters
10. - Record Support Routines
init_record
process
special
get_value
get_units
get_precision
get_graphic_double
get_control_double
get_alarm_double
11. - Record Processing
11.1. - process()
11.2. - execOutput()
Tim Mooney - March 27, 2006