Abstract: Threads of a computing environment are managed to improve system performance. Threads are migrated between processors to take advantage of single thread processing mode, when possible. As an example, inactive threads are migrated from one or more processors, potentially freeing-up one or more processors to execute an active thread. Active threads are migrated from one processor to another to transform multiple threading mode processors to single thread mode processors.

Abstract: A decimal multiplication mechanism for fixed and floating point computation in a computer having a coefficient mechanism without resulting leading zero detection (LZD) and process which assumes that the final product will be M+N digits in length and performs all calculations based on this assumption. Least significant digits that would be truncated are no longer stored, but retained as sticky information which is used to finalize the result product. Once the computation of the product is complete, a final check based on the examination of key bits observed during partial product accumulation is used to determine if the final product is truly M+N digits in length, or M+N?1 digits. If the latter is true, then corrective final product shifting is employed to obtain the proper result. This eliminates the need for dedicated leading zero detection hardware used to determine the number of significant digits in the final product.

Abstract: Mechanisms for utilizing a reduced lookup table circuit to perform an operation in a data processing device are provided. A first input value is input for selecting a subset of values from the reduced lookup table circuit. The reduced lookup table circuit stores only boundary cell values from a fully filled lookup table corresponding to the reduced lookup table circuit. The subset of values comprises only a subset of boundary cell values corresponding to the first input value. A second value is input and a comparison, by the reduced lookup table circuit, of the second value to each of the boundary cell values in the subset of boundary cell values is performed. The reduced lookup table circuit outputs an output value based on results of the comparison of the second value to each of the boundary cell values in the subset of boundary cell values.

Abstract: Machine instructions, referred to herein as a long Convert from Zoned instruction (CDZT) and extended Convert from Zoned instruction (CXZT), are provided that read EBCDIC or ASCII data from memory, convert it to the appropriate decimal floating point format, and write it to a target floating point register or floating point register pair. Further, machine instructions, referred to herein as a long Convert to Zoned instruction (CZDT) and extended Convert to Zoned instruction (CZXT), are provided that convert a decimal floating point (DFP) operand in a source floating point register or floating point register pair to EBCDIC or ASCII data and store it to a target memory location.

Abstract: Mechanisms for utilizing a reduced lookup table circuit to perform an operation in a data processing device are provided. A first input value is input for selecting a subset of values from the reduced lookup table circuit. The reduced lookup table circuit stores only boundary cell values from a fully filled lookup table corresponding to the reduced lookup table circuit. The subset of values comprises only a subset of boundary cell values corresponding to the first input value. A second value is input and a comparison, by the reduced lookup table circuit, of the second value to each of the boundary cell values in the subset of boundary cell values is performed. The reduced lookup table circuit outputs an output value based on results of the comparison of the second value to each of the boundary cell values in the subset of boundary cell values.

Abstract: Machine instructions, referred to herein as a long Convert from Zoned instruction (CDZT) and extended Convert from Zoned instruction (CXZT), are provided that read EBCDIC or ASCII data from memory, convert it to the appropriate decimal floating point format, and write it to a target floating point register or floating point register pair. Further, machine instructions, referred to herein as a long Convert to Zoned instruction (CZDT) and extended Convert to Zoned instruction (CZXT), are provided that convert a decimal floating point (DFP) operand in a source floating point register or floating point register pair to EBCDIC or ASCII data and store it to a target memory location.

Abstract: A processor includes a microarchitecture for working around a processing flaw, the microarchitecture including: at least one detector adapted for detecting a predetermined state associated with the processing flaw; and at least one mechanism to modify default processor processing behavior; and upon modification of processing behavior, the processing of an instruction involving the processing flaw can be completed by avoiding the processing flaw.

Abstract: A method, computer program product and a system for identifying decimal floating point addition operations that guarantee operand alignment and do not require alignment, normalization or rounding are provided. The method includes: receiving an instruction to perform an addition of a first operand and a second operand; extracting a first exponent (EXP) and a first most significant digit (MSD) from the first operand; extracting a second EXP and a second MSD from the second operand; and determining whether alignment between the first operand and the second operand is guaranteed, based on the first EXP, the first MSD, the second EXP and the second MSD.

Abstract: A system and method for converting from decimal floating point (DFP) into scaled binary coded decimal (SBCD). The system includes a mechanism for receiving a DFP number. The system also includes at least one of a mechanism for performing coefficient expansion on the DFP number to create a binary coded decimal (BCD) coefficient part of a SBCD number and a mechanism for performing exponent extraction on the DFP number to create an exponent part of the SBCD number.

Abstract: Error detection using parity compensation in binary coded decimal (BCD) and densely packed decimal (DPD) conversions, including a computer program product having a tangible storage medium readable by a processing circuit and storing instructions for execution by the processing circuit for performing a method. The method includes receiving formatted decimal data in a first format, the formatted decimal data consisting of a DPD format data or a BCD format data. One or more first parity bits are generated by converting the received data into a second format of the formatted decimal data, and by determining the parity of the data in the second format. One or more second parity bits are generated directly from the received data. An error flag is set to indicate an error in the data in the second format in response to the first parity bits not being equal to the second parity bits.

Abstract: A method for performing decimal division including receiving a scaled divisor and a scaled dividend into input registers. A subset of multiples of the scaled divisor is stored in a plurality of multiples registers. Quotient digits are calculated in response to the scaled divisor and the scaled dividend. Each quotient digit is calculated in three clock cycles by a pipeline mechanism. The calculating includes selecting a new quotient digit, and calculating a new remainder. Input to the calculating a new remainder includes data from one or more of the multiples registers.

Abstract: A method for implementing an adder including receiving a first and second operand. A sum of one or more corresponding digits from the first operand and the second operand is calculated. The calculating is performed by a plurality of adder blocks. Output from the calculating includes the sum of the corresponding digits and a carry out indicator for the corresponding digits. The sums of the corresponding digits and the carry out indicators in a carry chain are stored in an intermediate result register. Each of the sums in the intermediate result register is incremented by one. A selection between each of the sums and the sums incremented by one is performed. Input to the selecting includes the carry chain, and the output from the selecting includes a final sum of the first operand and the second operand. The final sum is stored in an output register.

Abstract: A method for performing a decimal floating point operation including receiving a first operand having a first coefficient and a first exponent into a first register. A second operand having a second coefficient and a second exponent are received into a second register. An operation, either addition or subtraction, associated with the first operand and the second operand is received. Three concurrent calculations are performed on the first operand and the second operand. The three concurrent calculations include: applying the operation to the first operand and the second operand based on a first assumption; applying the operation to the first operand and the second operand based on a second assumption; and applying the operation to the first operand and the second operand based on a third assumption. A final result is selected from the first result, the second result and the third result.

Abstract: A method for performing decimal multiplication including storing a multiplier and a multiplicand in operand registers, the multiplier including one or more digits. A running sum is stored in a shifter and initialized to zero. The method includes performing for each of the digits in the multiplier in order from least significant digit to most significant digit: creating a partial product of the digit and the multiplicand and adding the partial product to the running sum. The running sum is output as the result of multiplying the multiplier and the multiplicand. The performing and outputting are implemented by a mechanism that includes one or more two cycle adders connected to the operand registers, multiplicand multiples circuitry connected to the operand registers, and a result digits register connected to the two cycle adders.

Abstract: Binary code decimal (BCD) arithmetic add/subtract operations on two BCD numbers independent of which BCD number is of a greater magnitude include, responsive to the BCD arithmetic add/subtract operation being a subtract operation, performing a BCD arithmetic subtraction operation on a first BCD number and a second BCD number, the first BCD number having a first magnitude and the second BCD number having a second magnitude. The first magnitude is greater than, equal to, or less than the second magnitude. The performing includes: in parallel to a carry generation, partial sums or partial differences of the first and second BCD numbers are computer such that a final result in signed magnitude form is selectable from the partial sums or differences based on carry information without any post processing steps.

Abstract: A decimal multiplication mechanism for fixed and floating point computation in a computer having a coefficient mechanism without resulting leading zero detection (LZD) and process which assumes that the final product will be M+N digits in length and performs all calculations based on this assumption. Least significant digits that would be truncated are no longer stored, but retained as sticky information which is used to finalize the result product. Once the computation of the product is complete, a final check based on the examination of key bits observed during partial product accumulation is used to determine if the final product is truly M+N digits in length, or M+N?1 digits. If the latter is true, then corrective final product shifting is employed to obtain the proper result. This eliminates the need for dedicated leading zero detection hardware used to determine the number of significant digits in the final product.

Abstract: Several implementations and a design structure for decimal multiplication that uses a BCD 4221 encoding scheme, separate accumulation of partial products, accumulation of the partial products into a final product and conversion from and to a BCD 8421 coding scheme.

Abstract: A system for binary multiplication in a superscalar processor includes a first pipeline, an execution unit, and a first multiplexer; a first rotator in communication with one register of the first pipeline and the execution unit; and a leading zero detection register in communication with the execution unit and another register of the first pipeline; a second pipeline, a second execution unit, and a second multiplexer; a rotator in communication with one register of the second pipeline and the second execution unit; and a leading zero detection register in communication with the second execution unit and another register of the first pipeline; and a third pipeline, a binary multiplier in communication with a pair registers of the third pipeline; a general register; an operand buffer for obtaining first and second operands; and a bus for communication between the pipelines, the general register and the operand buffer.

Abstract: Error detection using parity compensation in binary coded decimal (BCD) and densely packed decimal (DPD) conversions, including a computer program product having a tangible storage medium readable by a processing circuit and storing instructions for execution by the processing circuit for performing a method. The method includes receiving formatted decimal data in a first format, the formatted decimal data consisting of a DPD format data or a BCD format data. One or more first parity bits are generated by converting the received data into a second format of the formatted decimal data, and by determining the parity of the data in the second format. One or more second parity bits are generated directly from the received data. An error flag is set to indicate an error in the data in the second format in response to the first parity bits not being equal to the second parity bits.

Abstract: Complex floating point instructions are executed under millicode control when it is not cost effective to implement its function in hardware. One of the disadvantages to executing complex instructions using millicode routines is that determining and accessing the instructions operands are costly for millicode performance. To determine what the source and target location are, the instruction text is parsed. Furthermore the millicode instruction stream must be modified to access the operand data from and write the result to the program registers specified by the complex floating point instruction. The invention overcomes these disadvantages by providing millicode with register indirect access to the program floating point registers.