Re: save array of floats into HDF5 as attribute

[Hinko Kocevar <hinkocevar@gmail.com>]

Hi Mark,

thanks for explaining! I managed to get the FTVL=CHAR waveforms to appear as strings in the HDF5 file, on another occasion.

What I want to save now are coefficients that need to be floats, chars (FTVL=CHAR) will not cut it.

I'll resort to defining 10 ai records instead of one waveform for now, since I need this in the coming days/weeks.

Will keep an eye on the #2 issue, though!

Thanks,

Hinko

On Tue, Sep 26, 2017 at 2:19 PM, Mark Rivers <rivers@cars.uchicago.edu> wrote:

I have updated the Github issue to raise the possibility of supporting arrays in NDAttributes by storing them as strings.

https://github.com/areaDetector/ADCore/issues/2

Mark

________________________________
From: Mark Rivers
Sent: Tuesday, September 26, 2017 7:12 AM
To: Hinko Kocevar; tech-talk@aps.anl.gov
Subject: RE: save array of floats into HDF5 as attribute

Hi Hinko,

> can I save an array of floats into HDF5 file through areaDetector Attribute?

No, unfortunately that is not possible.  There is a 4 year old issue in ADCore about this:
https://github.com/areaDetector/ADCore/issues/2

This is from NDAttribute.h

******************************************
/** Union defining the values in an NDAttribute object */
typedef union {
    epicsInt8    i8;    /**< Signed 8-bit integer */
    epicsUInt8   ui8;   /**< Unsigned 8-bit integer */
    epicsInt16   i16;   /**< Signed 16-bit integer */
    epicsUInt16  ui16;  /**< Unsigned 16-bit integer */
    epicsInt32   i32;   /**< Signed 32-bit integer */
    epicsUInt32  ui32;  /**< Unsigned 32-bit integer */
    epicsFloat32 f32;   /**< 32-bit float */
    epicsFloat64 f64;   /**< 64-bit float */
} NDAttrValue;

/** Structure used by the EPICS ellLib library for linked lists of C++ objects.
  * This is needed for ellLists of C++ objects, for which making the first data element the ELLNODE
  * does not work if the class has virtual functions or derived classes. */
typedef struct NDAttributeListNode {
    ELLNODE node;
    class NDAttribute *pNDAttribute;
} NDAttributeListNode;

/** NDAttribute class; an attribute has a name, description, source type, source string,
  * data type, and value.
  */
class epicsShareClass NDAttribute {
public:
    /* Methods */
    NDAttribute(const char *pName, const char *pDescription,
                NDAttrSource_t sourceType, const char *pSource, NDAttrDataType_t dataType, void *pValue);
    NDAttribute(NDAttribute& attribute);
    static const char *attrSourceString(NDAttrSource_t type);
    virtual ~NDAttribute();
    virtual NDAttribute* copy(NDAttribute *pAttribute);
    virtual const char *getName();
    virtual const char *getDescription();
    virtual const char *getSource();
    virtual const char *getSourceInfo(NDAttrSource_t *pSourceType);
    virtual NDAttrDataType_t getDataType();
    virtual int getValueInfo(NDAttrDataType_t *pDataType, size_t *pDataSize);
    virtual int getValue(NDAttrDataType_t dataType, void *pValue, size_t dataSize=0);
    virtual int getValue(std::string& value);
    virtual int setDataType(NDAttrDataType_t dataType);
    virtual int setValue(const void *pValue);
    virtual int setValue(const std::string&);
    virtual int updateValue();
    virtual int report(FILE *fp, int details);
    friend class NDArray;
    friend class NDAttributeList;


private:
    template <typename epicsType> int getValueT(void *pValue, size_t dataSize);
    std::string name_;              /**< Name string */
    std::string description_;       /**< Description string */
    NDAttrDataType_t dataType_;     /**< Data type of attribute */
    NDAttrValue value_;             /**< Value of attribute except for strings */
    std::string string_;            /**< Value of attribute for strings */
    std::string source_;            /**< Source string - EPICS PV name or DRV_INFO string */
    NDAttrSource_t sourceType_;     /**< Source type */
    std::string sourceTypeString_;  /**< Source type string */
    NDAttributeListNode listNode_;  /**< Used for NDAttributeList */
******************************************

So the value_ member is a union of the numeric data types, and it can store only a single value.

The exception is for strings, where the value is stored in the std::string string_ member.  There is effectively no length limit on strings.

If you change from DBR_NATIVE to DBR_STRING it will read the entire array as a string if the waveform record FTVL is CHAR.  So I was hoping this would work to read your array:

<Attribute name="GaussParams"  type="EPICS_PV" source="DTU:GaussParams"   dbrtype="DBR_STRING"  description="Gauss params"/>

However, I just tested this with a waveform record whose FTVL is DOUBLE and it only reads the first element, not the entire array.  I think that is something that would not be too hard to fix:  if the requested dbrtype=DBR_STRING then subscribe for callbacks on the entire array, not just the first element.

Would that be useful for you, i.e. having the array as a string rather than 10 numbers?

Mark

________________________________
From: tech-talk-bounces@aps.anl.gov [tech-talk-bounces@aps.anl.gov] on behalf of Hinko Kocevar [hinkocevar@gmail.com]
Sent: Tuesday, September 26, 2017 3:44 AM
To: tech-talk@aps.anl.gov
Subject: AD: save array of floats into HDF5 as attribute

Hi,

can I save an array of floats into HDF5 file through areaDetector Attribute?

XML definition:

<Attribute name="GaussParams"         type="EPICS_PV" source="DTU:GaussParams"                dbrtype="DBR_NATIVE"  description="Gauss params"/>

where PV is:

record(waveform, "$(P)$(R)GaussParams")
{
field(FTVL, "DOUBLE")
field(NELM, "10")
}


With the above, I only a single (first) value saved in the HDF5 file as opposed to all 10.

Thanks,
Hinko

--
.. the more I see the less I believe.., AE AoR

--

.. the more I see the less I believe.., AE AoR